Exam 1 Flashcards
(331 cards)
1
Q
Define hematopoiesis. Function
A
- Formation of blood cells in bone marrow
- Function: provide cellular elements of peripheral blood, delivery of o2 to tissues + host defense
2
Q
Define erythropoiesis. Location?
A
- Formation/production of RBCs that starts in embryonic yolk sac, continues in extramedullary organs (liver, spleen). Late fetal development is where erythropoiesis predominates in red marrow.
- If bone marrow is dysfunctional, liver and spleen can do hematopoiesis (called extramedullary hematopoiesis).
3
Q
What is a reticulocyte? Clinical use?
A
- Precursor to mature erythrocyte. Will be sent out from bone marrow to increase RBCs
- High retic count = potentially anemic process occurring.
4
Q
Define granulopoiesis.
A
- Production of cells in granulocytic lineage (N, E and B)
5
Q
What is a band? Clinical relevance?
A
- Precursor (slightly immature) granulocyte. Detected in CBC.
- If you suspect bacterial infection, will see an increase in these, which is called a left shift.
6
Q
Where are neutrophils found in the body? Where do they go to die?
A
- Circulating pool: blood in motion (~50%)
- Marginating pools: adhering to blood endothelial cells to extravasate (~50%) when called.
- Splenic phagocytes remove them from circulation when dead/dying.
7
Q
Monocytes vs macrophages
A
- Monocytes: circulating in blood (~8 hours), differentiate into macrophage when entering tissues.
- Macrophages: monocyte in tissue, lifespan of months to years.
8
Q
Define lymphopoiesis
A
- Production of cells in lymphocytic lineage (T, B lymphocytes and NK cells)
9
Q
Define thrombopoiesis
A
- Production of platelets (aka thrombocytes), which are anuclear cytoplasmic remnant of megakaryocytes.
10
Q
Function of platelets
A
- Hemostasis, limit bleeding and repair endothelium.
11
Q
Where are “dead” platelets processed?
A
- Liver or spleen
12
Q
Where are an emergency reserve of platelets in spleen found?
A
- Spleen
13
Q
Immature B cells express what? Mature B cells express what?
A
- Immature express IgM only
- Mature expresses IgM and IgD
14
Q
Describe T cell maturation
A
- Prothymocyte leaves bone marrow = blood = thymus (differentiation in mature T cells if fortunate, vast majority (>90%) die with +ve and –ve selection) = leave thymus to population lymphatic organs
15
Q
Precursor of thrombocytes
A
- Megakaryocytes undergo nuclear mitosis without cytoplasmic divisions (endomitosis) to produce large 32 N cell
- Each cell = 100-1000 platelets
16
Q
Chemical that stimulates thrombopoiesis
A
- Thrombopoietin, which promotes megakaryocyte production and stimulates endomitosis, which is cell division of megakaryocyte without cytoplasmic division.
17
Q
Lifespan of lymphocytes, RBCs, platelets and granulocytes
A
- Lymphocytes: years
- RBCs: ~ 4 months
- Platelets: 7-10 days
- Granulocytes: 6-8 hours, max a few days
- Monocytes/macrophages: monocytes hours to tissue then months to years
18
Q
Characteristics of HSCs
A
- Rise to progenitor cells of all lineages (multipotent)
- Highly proliferative
- Capable of self-renewal (making more of themselves) and differentiation (turning into something else)
- Not identifiable morphologically
19
Q
Function of stromal cells
A
- Provide microenvironment for differentiation of precursor cells. Primitive precursors bind firmly, maturing precursors are more non-adherent. Binding regulated by cell adhesion molecules.
- Examples of these cells = adipocytes, fibroblastoid cells and reticuloendothelial cells
20
Q
Roles that cytokines play.
A
- Drive cell differentiation pathways. There are progenitor cell cytokines (stem cell factors etc.) and end-stage cytokines to induce lineage-specific differentiation.
21
Q
What are granulocytes?
A
- Neutrophils, eosinophils and basophils
22
Q
G-CSF function. Clinical use?
A
- Released by macrophages at inflammatory site
- Circulates to bone marrow
- Function: production/release of granulocytes (mostly neutrophils) from bone marrow
- Clinical use:
1. ) Give to bone marrow stem cell donors to mobilize stem cells from BM to blood
2.) Give to patients who have had decreased granulopoiesis d/t chemotherapy. Will stimulate granulopoiesis.
23
Q
GM-CSF clinical use
A
- Increase myeloid cell recovery in bone marrow transplant patient. Note: more toxic than G-CSF = thrombosis and capillary leak syndrome
24
Q
EPO function. Clinical use?
A
- Produced by peritubular interstitial cells of kidney d/t hypoxia. Inhibition by high o2 pressure.
- Circulates to bone marrow
- Function: production and release of RBCs from bone marrow
- Clinical use: anemia d/t renal insufficiency
25
TGF-Beta function
- Downregulates stem cell growth/differentiation through downregulation of cell surface receptors for growth/differentiation cytokines
26
Make-up of bone marrow (yellow vs red) and contrast the bones that contain red marrow in a child vs. an adult
- Yellow: inactive, mainly adipose
- Red: active, hematopoiesis occurs here
- Child has all red marrow in 1st few years of life. By 18, red is found in ribs, sternum and pelvis. Extramedullary hematopoiesis can occur in spleen and liver.
27
Maturational changes that takes place during erythropoiesis as it matures in the bone marrow
- Cell size: large to small
- Nuclear:cytoplasmic ratio: high to low
- Nucleoli: present to no presence
- Cytoplasm stain: dark blue (basophilic) to light blue/reddish-pink indicating decrease in RNA
28
Absolute cell count vs differential count
- Absolute count: quantity of each cell type per volume
| - Differential count: relative count with % of each cell type
29
What is normal reticulocyte count?
- ~1% of RBCs
30
Which cells make up the largest component of bone marrow?
- Granulocytes
| - NLMEB
31
Why can RBCs not resynthesize damaged proteins?
- RBCs lose their nuclei before entering the circulation and mRNA disappears 1-2 days after release. Therefore there is no ability to replacement damaged molecules or to do protein synthesis.
32
Contrast intravascular and extravascular hemolysis
- Extravascular hemolysis: old RBCs that are inelastic are trapped by spleen and phagocytosed by macrophages. Bilirubin is the product of this process. Why? Macrophages process the Hb.
- Intravascular hemolysis: mechanical disruption leads to destruction of RBCs. Hemoglobin is the product of this process.
33
What is the purpose of RBC metabolism? What form of energy is required?
1. Keep iron reduced (Fe2+): NADH
2. Maintain K/Ca gradient: ATP
3. Keep protein thiol groups reduced: NADPH
4. Maintain cell shape: ATP
34
What is the source of ATP, ADH and NADPH in a RBC?
- ATP and NADH from glycolysis
| - NADPH from pentose phosphate pathway
35
What does a RBC do when there is too much ATP and it requires NADH?
- Problem is that you cannot keep doing glycolysis if the ATP/ADP ratio is offset, ie. you have too little ADP to ATP. Why? PG kinase and pyruvate kinase are ADP-requiring enzymes.
- Solution = energy clutch. Convert 1,3 BPG to 2,3 BPG and then to 3 PG via enzymes diphosphoglyceromutase and DPG phosphatase respectively, which bypasses the PG kinase reaction. Net result is no consumption of ADP, no production of ATP and still you can produce NADH.
36
Describe regulation of glycolysis, 2,3 bisphoglycerate synthesis (BPG) and PPP in RBC
- Glycolysis (production of NADH and ATP): hexokinase and PFK1 are inhibited by acidic pH, not responsive to standard triggers such as glucagon, epi and insulin.
- 2,3 BPG (production of NADH without consuming ADP or making ATP): diphosphoglyceromutase inhibited by low pH.
- PPP (production of NADPH): when NADPH is low, PPP pathway becomes active via activation of G6P DH enzyme.
37
Function of 2,3BPG with Hb
- When high, decreases affinity of o2 for Hb. When low, increases affinity. Ultimately though acidosis reduces 2,3BPG concentrations in RBCs and allows for increased delivery of o2 to hypoxic/acidic tissues when combined with lag times and Bohr effect (proton) at tissue level. See lecture for more information.
38
What is the role of the pentose phosphate pathway (PPP) in RBCS?
- Provide NADPH, which allows for antioxidant defense to occur in RBCs via glutathione reductase enzyme (keeps glutathione in reduced form).
39
Explain the importance of glutathione for the survival of RBCs.
1. Reduced glutathione donates electrons to convert h2o2 to h2o via glutathione peroxidase enzyme.
2. Reduced glutathione keeps sulfhydryl groups on proteins and enzymes in RBCs in reduced form.
** Note: oxidized glutathione is taken to reduced form via glutathione reductase, which requires NADPH.
40
G6P DH deficiency. Genetics/prevalence, pathology, signs, microscopy
- XR, prevalence in African/Med populations
- Pathology: non-spherocytic, hemolytic/normocytic anemia. Crises triggered by infections, h2o2 producing drugs and Fava beans.
- Signs: anemia, splenomegaly, jaundice
- Microscopy: bite cells (macrophages remove pieces of RBCs) under peripheral blood smear
41
Bite cells
- G6P DH deficiency
42
Pyruvate kinase deficiency. Genetics, pathology, signs, microscopy
- Genetics: hereditary, rare
- Pathology: cause of non-spherocytic hemolytic anemia. Not able to produce NADH. Crises not triggered by ROS as in G6P DH deficiency.
- Signs: anemia, splenomegaly, jaundice
- Microscopy: blebbing of membranes
43
What do RBCs fill with when losing metabolism? What do they spill out? What happens to shape?
- Fill with Ca
- Spill out K
- Lose biconcave shape
44
Enzymatic causes of non-spherocytic anemia
1. G6P DH deficiency: lack of NADPH = lack of antioxidant capacity, damaged RBC
2. Pyruvate kinase: lack of NADH/ATP, cannot keep Ca/K gradient, Ca fills cells, K leaves and lose shape.
45
What is the grey top tube used for?
- Inhibits glycolysis and is anticoagulant. Used for measuring glucose or lactate.
46
Describe the metabolism of cancer cells highlighting the role of HIF-1alpha and the Cori cycle.
- Tumor cells get energy from glycolysis. They operate under hypoxic conditions and expression HIF-1alpha, which = increases expression of gluc transporters and decreases activity of pyruvate decarboxylase complex. Since it then produces large amount of lactate, liver takes on this load via Cori cycle.
47
Defects that lead to spherocytic anemia (spherocytosis)
- Defects in cytoskeleton proteins lead to spherocytosis. AD inheritance prevalence = 1/2000.
- Most common defects = ankyrin mutation
- Less common = band 3, spectrin, protein 4.2 mutation
48
What is paroxysmal nocturnal hemoglobinuria? Describe pathology.
- Mutation in PIGA gene leads to a rare hemolytic anemia. Affected cells cannot synthesize the GPI anchor that tethers cell surface proteins to the membrane. These cells are susceptible to complement attack and therefore intravascular hemolysis occurs.
49
Which form of iron is useful in humans?
- Ferrous (Fe2+)
50
Why is free Fe2+ and Cu+ dangerous in the body?
- Electron captured from these onto oxygen to produce superoxide anion (o2-) and from h2o2 to produce OH- (hydroxyl radical), which is the worst radical).
51
Describe the dietary requirement for iron.
- ~ 10-20 mg/day. Note: plant iron is mostly Fe3+ and is not extracted very well. Animal iron is mostly heme-bound and more is taken up in comparison to plant iron (non-heme).
52
Where is iron hemostasis regulated? What are ways to lose iron from body?
- Uptake through release of Fe from enterocytes. Only way to lose iron is through blood loss, sloughed off intestinal/kidney cells and intravascular hemolysis (Hb in urine).
53
Describe the distribution of iron (functional vs storage pools) in the body.
- 80% in active form in Hb, Mb, cytochromes and transferrin (transporter protein of Fe).
- 20% in inactive form in ferritin (storage protein of Fe, water soluble form that is easily mobilized) or in hemosiderin (degradation form of ferritin, water insoluble and hard to mobilize).
54
What transports iron in the plasma?
- Transferrin
55
Where is iron stored?
- In ferritin in the following locations: enterocytes (temporary), liver, bone marrow and phagocytes
56
Describe iron uptake in duodenal enterocytes, passage to the plasma and then into cells.
- Fe2+ is transported into enterocytes via DMT1. Fe3+ form must first be reduced to Fe2+ via cytochrome on the apical membrane of the enterocytes. Heme is transported into the enterocyte via heme transporter.
- Once inside the cell, Fe associates with ferritin or exits the basolateral side of the cell via the ferroportin 1 transporter. It is oxidized into the Fe3+ via hephaestin on the basolateral aspect and then binds to transferrin.
- Transferrin binds transferrin receptors on cells, is endocytozed. Endosome is acidified causing release of Fe2+ from transferrin and movements of Fe2+ through DMT1 into cytoplasm where it can associate with ferritin (if stored).
57
Describe regulation of ferroportin 1
- Hepcidin (made by liver) inhibits passage of Fe from enterocyte into plasma by blocking the ferroportin 1 channel.
- When hepcidin is low, there is high uptake of Fe.
58
What is the pathological sign in a cell that Fe overload occurred?
- Hemosiderin = ferritin particle denature/degradation. In a hemolytic disorder, accumulation of ferritin and hemosiderin is seen in macrophages.
59
Function of hepcidin
- Regulation of iron uptake into the body. When high, ferroportin 1 channel on basolateral enterocyte is inhibited and Fe uptake cannot occur. When low, high uptake.
- Also regulates Fe release from macrophages.
60
Hereditary hemochromatosis is a defect in what?
- HFE, the upstream regulator of hepcidin. Mutation leads low hepcidin expression and therefore high Fe uptake into the body.
61
Regulation of synthesis of iron-handling proteins is through what mechanism? Explain. On what RNAs is the IRE (iron-response element) found? Describe what occurs when Fe levels are low and high.
- Post-transcriptional level.
- mRNAs are always present in the cell, but iron regulatory protein associates with the IRE (iron response element) hairpin loop. When associated, translation of mRNA cannot occur and you cannot synthesize protein.
- When Fe enters the cell, it binds to the iron regulatory protein, displacing it from the mRNA and now translation of iron-handling protein can occur.
- IREs are on the RNAs of ferritin (5’ UTR), ALA synthase (5’ UTR) and transferrin (3’ UTR) receptor. When iron binds to the regulatory protein associated with each of these, increase in translation of the respective protein occurs with the exception of the transferrin receptor RNA, where translation is repressed. Why? When Fe is high, don’t want receptor (transferrin) on cell surface to take up too much Fe, but you want to be able to handle the iron (ferritin and ALA synthase).
62
Is serum iron a good indicator for iron status in the body?
- No. Fe is stored or transferred as complex to protein mostly, so this value would provide no information about stores.
63
What does high TIBC mean? What does high transferrin saturation mean?
- Total iron binding capacity = unoccupied Fe sites on transferrin.
- TIBC = transferrin that isn’t occupied by Fe. When high, Fe stores are low.
- Transferrin saturation = transferrin that is occupied by Fe. When high, Fe stores are high.
64
What is serum ferritin?
- Fraction of ferritin present in body
65
What is the best measure for body iron stores?
- Ferritin. Not often used as you can find out stores through TIBC (if high, Fe stores low).
66
What is red cell protoporphyrin? What does a high value of this mean?
- Protoporphyrin is iron-free precursor of heme. High value = low Fe. This is sensitive early indicator of insufficient Fe.
67
Lab values for Fe status in the body
- Serum iron
- TIBC
- Transferrin saturation
- Serum ferritin
- Red cell protoporphyrin
68
Causes for iron deficiency
- Chronic blood loss
- Chronic dz (hepcidin production up = Fe intake inhibited)
- Poor dietary intake
- Intestinal parasites (compete for Fe)
- Malabsorptive dz (Celiac)
69
Describe the progression of iron deficiency anemia. What are the clinical values seen?
1. Iron depletion, serum ferritin decreases
2. Deficient erythropoiesis, protoporphyrin levels up, transferrin saturation decreases
3. Iron deficiency anemia (microcytic hypochromic anemia)
70
Causes of iron overload. Lab signs?
- Blood transfusion (Fe accumulates in macrophages)
- Slow erythropoiesis (renal failure)
- Hereditary hemochromatosis type 1 (HFE mutation = low hepcidin = increased iron uptake)
- Lab signs = high transferrin saturation
71
What is the regulated step of heme synthesis? What are the substrates for that reaction? How is this enzyme regulated?
- Glycine + succinly-CoA = ALA (aminolevulinic acid) via ALA synthase
- Heme feeds-back negatively on this enzyme to inhibit
72
Describe synthesis of heme. Note the committed step and regulation.
1. Glycine + succinyl-CoA = ALA (aminolevulinic acid) via ez: ALA synthase. Note this is regulated step. Heme inhibits this enzyme when [ ] too high.
2. ALA = PBG via ez: PBG synthase (aka ALA dehydratase)
3. Ez: PBG deaminase
4. Ez: UPG III synthase
5. UPG III = CPG III via ez: UPG III decarboxylase
6. Protoporphyrinogen IX + Fe2+ = heme via ez: ferrochelatase
73
How can you tell which porphyrias are photosensitive and which are not?
- Where is defect? If before UPG III synthesis, then not. If after, then it is. UPG III absorbs light in UV spectrum.
74
Acute intermittent porphyria (AIP). Pathology, signs/symptoms
- Pathology: PBG deaminase defect/deficiency causing ALA and PBG to accumulate in circulation and urine.
- Signs/symptoms: Dark red color (ALA and PBG), life-threatening with episodes of confusion and sharp abdominal pain. Drugs, etoh and starvation precipitate. Mnemonic = 5 Ps (painful abdomen, port-wine urin, polyneuropathy, psych disturbances, precipitated)
75
Porphyria cutanea tarda (PCT). Pathology, signs/symptoms
- Pathology: Defect/deficiency of UPG III decarboxylase leading to buildup of photosensitive porphyrins.
- Signs/symptoms: Porphyrins detected in urine, photosensitivity of skin leading to blistering of exposed skin.
76
Explain how etoh and certain drugs trigger a porphyria attack.
- Etoh consumptions and certain drugs will induce synthesis of cytochromes for production of P450. Cytochromes are heme dependent requiring porphyrin precursors.
77
Effect of lead on heme synthesis
- Inhibits ALA dehydratase (aka PBG synthase) and ferrochelatase. This leads to accumulation of ALA and other heme precusors. Symptoms similar to porphyrias.
78
Describe the quaternary structure of hemoglobin. Compare and contrast the structure and oxygen binding properties of hemoglobin and myoglobin.
- Hemoglobin structure: Tetramer, 2 alpha, 2 beta globin chains with interactions stabilized by non-covalent forces.
- Each subunit has a heme group that don’t bind o2 with equal affinity.
- Hb doesn’t bind efficiently at low o2 concentration, which is in contrast to Mb. As o2 increases, becomes more efficient at binding.
- Hb has sigmoid curve, Mb has hyperbolic curve.
79
How do 2,3-BPG, CO2 and H+ influence the oxygen affinity of hemoglobin? What is the physiological importance of these chemicals?
- 2,3 BPG, high CO2 and high [H+] (low pH) favors o2 dissociation from Hb. Physiologically this is important in peripheral tissues where this environment exists.
- Conversely in lungs where low CO2, low [H+] (high pH) exists, o2 association to Hb is favored.
80
What are the forms of Hb in adults? Which is most abundant?
- HbA (2 x alpha and 2 x beta globins): most abundant
| - HbA2 (2 x alpha and 2 x delta globins)
81
What are Hb F, Hb A, Hb A2, Hb Gower 1, Hb Gower 2 and Hb Portland? What is the subunit composition of each? At what stages of development is each hemoglobin form produced? Why do we care?
- Hb F = alpha2, gamma2
- Hb A = alpha2, beta2
- Hb A2 = alpha2, delta2
- Hb Gower 1 = zeta2, epsilon2
- Hb Gower 2 = alpha2, epsillon2
- Hb Portland = zeta2, gamma2
- Hb Gower and Portland are expressed in early embryonic development. They are replaced with Hb F, the major fetal Hb. As development progresses, there is a reciprocal switch between gamma-chain synthesis and beta-chain synthesis leading to replacement of Hb F with Hb A. Hb F
82
How do the oxygen-binding properties of the embryonic hemoglobins and Hb F differ from those of the adult forms? Why is this important? What is the molecular basis for the difference in oxygen affinity between Hb F and Hb A?
- Gower and Portland Hb have very high o2 affinity capturing o2 from mother and delivering it to fetus. This is necessary d/t the lack of functional circulatory system in early development.
- Hb F has Serine in gamma-chain. Hb A has His in beta-chain with higher affinity for 2,3 BPG. Since Hb F lacks BPG affinity, meaning there is increased affinity of Hb F for o2.
83
Which types of globin chain are considered α-like? Which are considered β-like? Describe the organization of the α-globin loci on its chromosome and the organization of the β-globin loci on its chromosome.
- Alpha-like = alpha and zeta found on c/s 16
- Beta-like = beta, gamma, delta and epsilon found on c/s 11
- C/s #16: zeta genes, psi genes (pseudo genes), alpha genes. HS-40 upstream of these genes.
- C/s #11: epsilon, gamma, psi gene (pseudo genes), delta and beta genes. LCR region upstream of these genes.
84
What are hemoglobinopathies? Groups of hemoglobinopathies?
- Disorders of hemoglobin
1. Structural variants: mutations that produce unstable Hbs. These are rare. More common: Hb S, Hb C and Hb E.
2. Thalassemias: imbalanced synthesis of globin chains
85
What are Heinz bodies?
- Unstable Hbs have a tendency to form insoluble complexes that become oxidized to methemoglobin (Fe3+) and subsequently form hemichrome. Aggregates precipitate as Heinz bodies and hemolytic anemia results.
86
Give examples of rare structural variants of Hb
- Hb-Helsinki: mutation in beta-subunit from Lys to Met at 2,3 BPG site = increased o2 affinity
- Hb-Kansas: mutation in beta-subunit from Asn to Thr at a1b2 contact site = decreased o2 affinity
- Hb M-Boston: alpha-subunit mutation (His-Tyr distal) form methemoglobin
- Hb M-Hyde Park: beta-subunit mutation (His-Tyr proximal) form methemoglobin
87
Hb S. What is it? Describe mutation and properties of the mutant Hb. Treatment?
- This is sickle cell disease, a structural variant of Hb.
- Mutation: Glut – Val in beta-globin chain at position #6
- Properties: deoxygenated Hb S polymerizes = distorted shape of RBC = lyse = chronic hemolytic anemia
- Note: heterozygotes = sickle cell trait, while homozygotes = sickle cell dz.
- Tx: hydroxyurea (HU) is an antineoplastic agent that increases expression of Hb F promoting the solubility of Hb. It reduces sickling, painful crises and hospitalizations d/t unknown mechanism.
88
Hb C. What is it? Describe mutation and properties of the mutant Hb.
- A structural variant of Hb, restricted to those of W. African origin.
- Mutation: Glut – Lys in beta-globin chain at position #6
- Properties: Hb C is less soluble than Hb A and precipitates leading to less flexible cells = hemolytic anemia. No sickling seen.
89
Hb E. What is it? Describe mutation and properties of the mutant Hb.
- A structural variant of Hb (most common of them, but least severe). Common in SE Asia.
- Mutation: Glut – Lys in beta-globin chain at position # 26 = ineffective synthesis.
- Properties: Mutant beta-globin isn’t synthesized effectively = imbalanced alpha-beta globin chain (mild thalassemia).
- Note: heterozygotes (trait) = asymptomatic. Homozygotes = typically microcytotic anemia, hypochromia.
90
What is thalassemia? Most common thalassemias? What is meant by α°, α+, β°, and β+ in relation to thalassemia?
- Thalassemia = reduced synthesis of either type of globin chain resulting in decreased functional tetramer in Hb leading to anemia.
- Most common = alpha and beta-thalassemia.
- Alpha (0) and beta (0) thalassemias = no functional globin chain produced
- Alpha+ and beta+ thalassemias = reduced amount of globin chain produced
91
Why are α-thalassemias manifest in both fetal and adult life?
- Two genes for alpha-globin on c/s 16
- Alpha chains are found in embryonic Hb (Gower 2, Hb F) and in adult Hb and therefore alpha-thalassemias can be found through development and adult life.
92
What are the four possible alpha-thalassemia states?
- States (a and b considered carrier states)
a. ) 3 functional / 1 defective = no clinical signs
b. ) 2 functional / 2 defective = mild thalassemic anemia
c. ) 1 functional / 3 defective = severe alpha-deficiency. In fetus, Bart’s hemoglobin (gamma4-tetramers) seen. After birth, Hb H (beta4-tetramers) seen. Both are poor o2 carriers. Hb H precipitates = hemolysis.
d. ) 4 defective = alpha(0) thalassemia. Only embryonic Hbs Gower and Portland can be produced. No adult Hb can be produced. Leads to Hb Bart’s hydrops fetalis syndrome, a lethal condition.
93
Bart’s hemoglobin
- Alpha-thalassemia with 1 functional alpha-globin gene and 3 defective. This Hb is gamma-4 tetramer in fetus and is a poor o2 carrier.
94
Hb H
- Alpha-thalassemia with 1 functional alpha-globin gene and 3 defective. This Hb is beta-4 tetramer after birth and is poor o2 carrier and precipitates in blood leading to hemolytic anemia.
95
Cause of alpha-thalassemias?
- Most often arise by deletion through homologous recombination (at meiosis)
- There are also various point mutations seen as in Hb-constant spring
96
Hb-constant spring. What is it? What is the mutation and the expected phenotype given this?
- This is alpha-thalassemia d/t point mutation. T is replaced with C leading to stop codon conversion to non-stop (glutamine). Alpha-globin chain has increased length.
- This Hb only contributes a small amount of total Hb as mRNA for this alpha-globin is unstable. This behaves like an alpha+ thalassemia
97
What are the beta-thalassemia states?
- Only one gene on c/s 11.
- 1 functional gene / 1 defective = asymptomatic (lower MCV, MCH, increased level Hb A2)
- Homozygous defect = severe phenotype?
98
Cause of beta-thalassemias?
- Deletion through homologous recombination events
99
What is HbLepore? How is HbLepore formed?
- Recombination event at c/s 11 deletes part of both beta and delta globin genes. This leads to the lepore fusion globin, which functions poorly as chain. Trait is asymptomatic, but disease is rare and severe.
100
Describe a case where a point mutation gives rise to a β+-thalassemia.
- Best characterized point mutations that give rise to these thalassemias affect splicing. Mutation away from true splice site (eg. T to A) leads to reduced message as splicing now occurs in both locations.
101
What is hereditary persistence of fetal hemoglobin?
- One type of deletion on c/s 11 leads to removal of both the beta and delta globin genes leaving only gamma genes on that c/s. This could lead to selection for RBCs that contain Hb F (alpha2, gamma2).
102
What are some advantages and disadvantages of the use of electrophoresis in the analysis of hemoglobin variants?
- Electrophoresis technique used typically in screening of neonate for hemoglobinopathies.
- Pro: cheap, easy
- Con: somewhat insensitive, if present at low concentrations, it might not be detected. Also some problems with co-migration of some Hb variants on gel
103
How is restriction fragment length polymorphism used to identify individuals who carry particular hemoglobin mutations?
- Restriction endonuclease is necessary to remove a known sequence and thereafter PCR primers amplify a region of globin gene that is suspected to have mutation. With this technique, you need to have a suspect mutation that you are searching for.
104
What are some important dietary sources of folate? What structural feature distinguishes dietary folates from the folate found in vitamin supplements?
- Folate (B9) in green leafy veg (spinach, lettuce, broccoli). Note: removed by prolonged cooking.
- Dietary folate exists as a family of compounds containing multiple glutamic acid residues. That found in vitamin supplements contains only one glutamic acid residue.
105
What enzyme converts folate to tetrahydrofolate (THF)? What drug is an inhibitor of this enzyme?
- THF = functional form. Folate converted to dihydrofolate, which is then converted to THF by dihydrofolate reductase.
- Inhibitor drug = methotrexate
106
What is the most oxidized form of THF? What is the most reduced form?
- Most oxidized = N10-formyl THF
| - Most reduced = N5-methyl THF
107
Function of THF
- One-carbon pool carrier
108
Which reaction is the source of most of the carbon in the one-carbon pool?
- Serine + THF = glycine + N5, N10-methylene-THF + water (ez = serine hydroxymethyltransferase)
109
Describe how dietary folate is absorbed in the intestine and then released into the circulation. What is the major form of THF in the circulation?
- Polyglutamate form of folic acid is hydrolyzed at brush border of intestinal lumen into monoglutamate form. This is absorbed into the intestinal cell and reduced and methylated into N5-methyl THF (most reduced) form. This is the form absorbed into the mesenteric circulation.
110
How is folate taken up from the circulation? What happens to folate inside the cell? Why is this modification important?
- N5-methyl THF (most reduced form) taken up via receptor-mediated endocytosis
- Once inside, it is metabolized and polyglutamate is added to retain folate within cells
111
What reactions require THF (or form)? Which appears to be of greatest clinical importance?
- Serine/glycine conversion, methionine synthesis, thymidylate synthesis, purine synthesis and histidine catabolism.
- Most importance = thymidylate synthesis where dUMP is converted to dTMP via thymidylate synthase. This is essential for DNA synthesis.
112
What is the ultimate source of all vitamin B12? What are some important dietary sources?
- Ultimate source = bacteria.
| - Dietary sources = liver, kidney, other meats, dairy and shellfish. NOT made by plant foods!
113
What are the metabolically active forms of vitamin B12?
- Adenosylcobalamin and methylcobalamin
114
Describe how vitamin B12 is liberated from food and absorbed in the intestine.
- B12 liberated from food in the stomach with secretions. Binds to R-proteins and travels to duodenum where pancreatic enzymes degrade R-protein, releasing B12, which then associates with IF (released from parietal cells in stomach). This complex is absorbed in ileum.
115
Describe how vitamin B12 is transported in the blood and taken up by tissues.
- Ileal mucosals cells make transcobalamin. B12 likely secreted into blood as complex with this. Taken up by cells via receptor-mediated endocytosis when complexed with TC. Note: most B12 in circulation is bound to haptocorrin.
116
Function of haptocorrin
- Most B12 in circulation is bound to haptocorrin. It is degraded by liver and B12 is secreted into bile. B12 again binds haptocorrin. It is digested in duodenum, B12 is released and binds intrinsic factor. This is reabsorbed in ileum and the process begins again. This is proposed as a circulating store of B12.
117
Pernicious anemia. Tx
- Lack of ability to absorb B12 from ileum d/t autoimmune dz leading to gastric atrophy and lack of IF production.
- Tx = IM injection or PO. In history, special diet containing liver was prescribed.
118
What is the Schilling test? Describe how Part 1 and Part 2 of the test are performed. What does an abnormal Part 1 but normal Part 2 tell you? How about abnormal Part 1 and Part 2?
- Schilling test: measures ability of patient to absorb B12
- Part 1: give oral load of radioactive B12, inject non-radioactive B12 to saturate circulating B12-binding proteins, start 24 hour urine catch, normal individuals excrete at least 7% of radioactivity within 24 hours.
- Part 2: give oral load of radioactive B12 with purified intrinsic factor and proceed as above.
- If part 1 abnormal and part 2 normal = pernicious anemia diagnosis (IF production defect)
- If both abnormal: defect in B12 absorption independent of IF production. Could be d/t transcobalaminc receptor defect.
119
Which metabolic processes require B12?
- Propionate metabolism: methylmalonyl-CoA mutase (requires adenosylcobalamin form)
- Homocysteine metabolism: methionine synthase (requires methylcobalamin form)
120
Describe the role of adenosylcobalamin in propionate metabolism. Describe deficiency in this?
- Propionate metabolism is necessary for feeding VOMIT (valine, odd chain FAs, methionine, isoleucine and threonine) into the TCA cycle.
- Methylmalonyl-CoA mutase requires B12
- Deficiency means that L-methylmalonyl-CoA accumulates leading to an organic acidemia.
121
Describe the role of methylcobalamin in homocysteine metabolism.
- Homocysteine + N5-methyl-THF (most reduced form) converted into methionine and THF via ez: methionine synthase (w/ methylcobalamin form of B12). Note regeneration of THF.
122
What is meant by the ‘methyl trap hypothesis’?
- Only methionine synthase reaction can convert N5-methyl THF back to THF.
- B12 deficiency prevents synthesis of methylcobalamin (active form of B12). Lack of this blocks THF synthesis pathway and folate becomes trapped in N5-methyl THF (most reduced) form. This results in a functional folate deficiency (sufficient folate in diet, insufficient state in cells).
123
What is the neurological consequence of B12 deficiency?
- Demyelination.
- Etiology: d/t failure of methionine synthase rxn. Some patients with demyelination d/t deficiency shown improvement with methionine administration. Mechanism unclear (? SAM).
124
Why does deficiency of either folate or vitamin B12 result in a megaloblastic anemia?
- B12 deficiency leads to functional folate deficiency (cannot re-synthesize THF and accumulate N5-methyl THF. Dietary deficiency leads to actual folate deficiency.
- In either case, thymidine synthesis is blocked as thymidylate synthase requires N5, N10-methylene THF. Purine synthesis is blocked as it requires N10-formyl THF. Ultimately: DNA synthesis is prevented.
- Most important = inhibition of thymidylate synthase. dUTP incorporate into DNA instead of dTTP. Cells grow, but cannot divide = megaloblastic. Most rapidly-dividing cells implicated. Apparent in RBCs as megaloblastic anemia.
125
What circumstances might increase folate needs? Under what circumstances may folate deficiency be seen in a patient?
- Increased need: pregnancy, lactation, growth, chronic hemolytic anemia.
- When is folate deficiency seen: alcoholism, old age, poverty, celiac or other conditions of malabsorption
126
What circumstances might increase vitamin B12 needs? Under what circumstances may vitamin B12 deficiency be seen in a patient?
- Increased need: pregnancy, periods of growth
- When deficiency is seen: strict vegans, pernicious anemia, celiac or other malabsorption dz, gastric acid insufficiency, ileitis/ileus resection, fish tapeworm infestation (Diphylobothrum latum), competing intestinal flora.
127
By what mechanism can nitrous oxide anesthesia provoke an acute megaloblastic anemia?
- NO destroys methylcobalamin
128
Microcytic vs macrocytic RBCs. How are these defined using MCV?
- Microcytic = smaller than avg RBCs. MCV 100 fL
129
Classification of anemias
- Etiology:
a. blood loss (acute vs chronic)
b. impaired production (genetic defects, deficiencies, EPO deficiency, immune-mediated injury of progenitors, inflammation-induced sequestration, primary hematopoietic neoplasms, space-occupying lesions, infection of RBC progenitors)
c. increased destruction (RBC membrane disorders, enzyme deficiencies, Hb abnormalities)
d. acquired (deficiency of PIGA, antibody mediated, mechanical trauma)
- MCV:
a. Microcytic: iron deficiency, ACD, thalassemia, sideroblastic anemia
b. Macrocytic: vit B12/folate deficiency, etoh use, liver dz, reticulocytosis, myelodysplastic syndrome, HOthyroidism
c. Normocytic: acute blood loss, aplastic anemia, ACD, renal dz, early iron dz, intrinsic RBC defect (membrane, Hb, enzyme), extrinsic RBC defect (autoimmune hemolytic anemia, PNH, microangiopathic hemolytic anemia)
130
Normal RBC volume
- 80 – 100 fL
131
Components of CBC
- Hb, Hct (or PCV: packed cell volume), RBC count, RBC indices (MCV, MCH, MCHC), RDW, WBC (TLC: total leuk count and differential leuk count), platelet count, evaluation of PBS (peripheral blood smear).
132
What is a reticulocyte count?
- Assessment of erythropoietic activity. Retics are newly released precursor RBCs (within 24 hours) from bone marrow. Use supravital stains to detect RNA filoments in cytoplasm.
- High reticulocyte percentage = anemia.
133
What is ESR?
- Erythrocyte sedimentation rate. This is a clue to underlying organic dz.
134
Causes of microcytic anemia. What is the most common? Least common?
1. Iron deficiency (most common)
2. ACD: anemia of chronic disease
3. Thalassemia
4. Sideroblastic anemia (least common)
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What lab tests can be ordered to test for microcytic anemia?
- CBC
- Serum Fe, TIBC, transferrin saturation and serum ferritin
- Hb electrophoresis to check for thalassemia (gold standard for mild beta-thalassemia)
136
What is the single best test for iron studies?
- Serum ferritin
137
Describe lab values of the following tests as seen in an IDA (iron deficiency anemia) patient: Hb/Hct, MCV, serum iron, TIBC, transferrin saturation, serum ferritin, marrow iron.
- Hb/Hct: low
- MCV: low (microcytic – less Hb in RBCs) – will see reticulocytosis
- Serum iron: low
- TIBC: high
- Transferrin saturation: low
- Serum ferritin: low
- Marrow iron: absent
138
Describe lab values of the following tests as seen in an ACD (anemia of chronic disease) patient: serum iron, TIBC, transferrin saturation, serum ferritin, marrow iron.
- Serum iron: low
- TIBC: normal or low
- Transferrin saturation: low
- Serum ferritin: normal or increased
- Marrow iron: normal or increased
139
Classification of immune hemolytic anemias. Which is most common?
- Drug-induced
- Auto-immune (most common): SLE (F > M), warm type (IgG abs) 70%, cold type (IgM abs + complement) 30%
- Allo-immune: HDONB, hemolytic transfusion rxn
140
Lab test to detect immune (transfusion, auto-immune) hemolytic anemias
1. DCT: direct (antiglobin) Coombs test: use patients RBCs and incubate with anti-human antibodies. If agglutination (linkage) occurs between RBCs, then positive result.
2. ICT: indirect (antiglobin) Coombs test: use patients serum containing antibodies. Donor’s blood is added to serum. Add anti-human antibodies to solution. If agglutination occurs, positive result.
141
Agglutination
- RBC antigen:antibody reaction leads to clumping
142
Lymphoma vs leukemia
- Lymphoma: lymphoid neoplasm arising as a discrete mass
| - Leukemia: lymphoid neoplasm with involvement of blood and bone marrow
143
Immunophenotyping
- Identifying cell type by protein expression (via IHC or flow)
144
What is cytogenetics/FISH?
- Identifying cells by chromosomal aberrations
145
Clinical presentation of lymphoma
- Fatigue, malaise, night sweats, fever, weight loss and painless, non-tender lymphadenopathy
146
Describe step wise process for diagnosis of lymphoid neoplasm
1. ) Morphology: via H&E.
a. Low power: Determine if lymph node architecture is preserved or effaced (loss of B and T cell areas). If effaced, what is pattern? Nodular, diffuse or both?
b. High power: Do cells look similar (monomorphic) or are there multiple cell types (polymorphic)? What are the sizes of cells (small, intermediate, large)? What is the shape of nucleus (irregular, regular and round)?
2. ) Immunophenotype (via IHC and flow): with morphology, determine if immature lymphoid cell or mature. If immature = lymphoblasts. If mature = mature (peripheral) lymphoma.
3. ) Chromosomal aberrations (via Cytogenetics/FISH) and clonality (via PCR): determine clonality to determine prognostic category and therapy targets.
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B-cell markers
- CD20, CD19 and lambda light chain
148
CD3
- T-cell marker
149
Evidence of clonality in B-cell lymphoma
- IHC: 1 type of Ig light chain produced
| - PCR: Ig heavy chain gene rearrangement
150
Evidence of clonality in T-cell lymphoma
- IHC: loss of specific CD antigen
| - PCR: TCR gene rearrangement
151
WHO classification of tumors of hematopoietic and lymphoid tissues
1. Clinical features: age, location and sites (where and #)
2. Morphology
3. Immunophenotype
4. Cytogenetics
5. Molecular analysis
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Main categories of lymphoma
1. Precursor B-cell neoplasms (immature B-cells)
2. Peripheral B-cell neoplasms (mature B-cells)
3. Precursor T-cell neoplasms (immature T-cells)
4. Peripheral T-cell and NK-cell neoplasms (mature T-cells and NK cells)
5. Hodgkin lymphoma (Reed-Sternberg cells and variants)
153
Lymphoma staging
I: single lymph node region or extra-lymphatic site (I (sub) E)
II: two or more LN regions or extra-lymphatic site (II (sub) E)
III: LN regions or extra-lymphatic sites (III (sub) E) on both sides of diaphragm
IV: disseminated or diffuse involvement of one or more extra-lymphatic sites
- In addition to numbering, lettering given. A = asymptomatic. B = fever, night sweats or > 10% weight loss
154
52 yo female c/o worsening fatigue for several weeks. CBC is done and she has a low RBC and low Hb and Hct levels. The next value to look at one the CBC to try and differentiate the possible type of anemia she may have is:
A. packed cell volume (PCV)
B. red cell distribution width (RDW)
C. mean corpuscular volume (MCV)
D. mean corpuscular Hb (MCH)
E. mean corpuscular Hb concentration (MCHC)
- Answer = C (MCV)
155
Nodular vs diffuse lymphoma pictures
- See L6
156
Monorphic vs polymorphic cell pictures
- See L6
157
Anemia. Define. What clinical lab values will you that your patient has anemia?
- Anemia: decreased red cell mass affecting tissue oxygenation. Note: Anemia is never a final diagnosis, you must find underlying reason.
- Labs: low Hb or low Hct
158
Morphology of normal RBCs under a PBS
- Cells must not be piled up under PBS. They should be barely touching at the zone of morphology (area between thickest smear and thinnest smear).
Characteristics:
- Normochromic: normal amt of Hb, shown by zone of central pallor that is ~ 1/3rd diameter of RBC
- Minimal anisocytosis (RBCs of unequal size): uniform, low RDW
- Minimal poikilocytosis (abnormally shaped): round
- Other: no nucleated RBCs, no infectious organisms within, no iron aggregates, no HJ bodies, size of RBC should be about the size of lymphocyte nucleus.
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Hyperchromic RBCs
- Without central pallor
160
Hypochromic RBCs
- Central pallor is greater than 1/3rd diameter of the cell
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What are polychromatic RBCs?
- RBCs with more than one color. Can have varying degrees of blues/grays. This indicates reticulocytes have been formed. Varying degrees of color indicates varying amount of RNA contained within.
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What is normoblastemia?
- Presence of nucleated RBCs in PBS. Can be seen during hemolytic anemias.
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What are spherocytes? Causes?
- RBCs with loss of central pallor
| - Causes: hereditary spherocytosis, autoimmune hemolytic anemia
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What are schistocytes? Causes?
- Divided/broken RBCs
| - Causes: microangiopathic hemolytic anemia (DIC, TTP, HUS), other hemolytic anemias
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What are the causes of punctate basophilia / basophilic stippling?
- Lead poisoning (severe anemia) primarily, also severe infection, drug exposure, alcoholism. Note per Volker’s lecture, it can be thalassemia (alpha)
166
Causes of Howell-Jolly bodies
- Absence of spleen (post-splenectomy) primarily, hemolysis
167
Causes and pathogenesis of microcytic anemias
1. ) Defects in heme synthesis
- Iron deficiency, ACD, sideroblastic anemia
2. ) Defects in synthesis of globin chains (alpha/beta)
- alpha and beta-thalassemias
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Macrocytic anemia causes (common and uncommon). Pathogenesis?
- Common = vit B12/folate deficiency, etoh use, drug use, liver dz
- Uncommon = myelodysplastic syndrome, hypothyroidism
- Pathogenesis = two groups
1. Defective DNA synthesis (B12/folate deficiency)
2. Increased RBC membrane (etoh use)
Note: Mnemonic for causes = BIG TEN. B12 malabsorption, inherited, GI dz or surgery, folic acid deficiency, alcoholism, thiamine responsive, retics miscounted as large RBCs, endocrine (hypothyroid), dietary, chemo drugs, erythro (leukemia), liver dz, Lesch-Nyhan syndrome, splenectomy.
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Causes of normocytic anemia (least NB if you don’t have time)
1. Retic count 3%
a. Intrinsic RBC defect
i. membrane defects: hereditary spherocytosis, hereditary eliptocytosis, PNH
ii. abnormal Hb: sickle cell
iii. defective enzyme: G6P DH deficiency, pyruvate kinase deficiency
b. Extrinsic RBC defect
i. Autoimmune hemolytic anemia, PNH, microangiopathic hemolytic anemia
170
Describe what happens to a patient after acute blood loss if they survive.
- If patient doesn’t die d/t cardiovascular collapse and shock, the following…
a. ) Water shift from interstitial fluid compartment to intravascular compartment = hemodilution indicating by low PCV.
b. ) Reduced oxygen = EPO stimulates erythroid hyperplasia and reticulocytes appear in peripheral blood after ~ 5 days
171
Cause of acute blood loss
- External blood loss: trauma, peptic ulcer etc. Leads to loss of Fe.
- Internal blood loss: ruptured abdominal aortic aneurysm. Fe recaptured.
172
General symptoms of all anemias. In children?
- Fatigue, dyspnea (esp. DOE), weakness, loss of stamina, exercise intolerance, dizziness, palpitations, headaches
- If severe: confusion, tachycardia, hypotension, syncope…death
- Children: poor feeding, irritability
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What are normal CBC values pertaining to RBC (Hb, Hct, RBC, MCV, MCH, MCHC, RDW)?
- Hb: males 14-17.5 g/dL, females 12-15
- Hct: males 42-50%, females 36-44
- RBC: males 4.5-6.0 M, females 4.0-5.0
- MCV: 80-100 fL
- MCH: 30-40 pg
- MCHC (Hb/Hct): 30-436%
- RDW: 13-15% (smaller = more uniform)
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What are normal values for serum Fe, TIBC, saturation of transferrin and ferritin?
- Serum Fe: 60-150 mcg/dL
- TIBC: 300-360 mcg/dL
- Saturation of transferrin: 20-50%
- Ferritin: 40-200 mcg/L
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Causes of Fe deficiency
- Inadequate absorption
- Inadequate utilization
- Excessive loss (most common)
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Where is iron absorbed?
- First and second parts of duodenum
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In what environment is iron best absorbed from GI tract?
- Acidic
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Effect of IL-6 on hepcidin
- Upregulates it = reduce Fe uptake from enterocytes by blocking ferroportin
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Effect of ferritin on hepcidin
- Upregulates it = reduce Fe uptake from enterocytes by blocking ferroportin
180
Effect of hypoxia on hepcidin
- downregulates it = increase Fe uptake from enterocytes by not inhibiting ferroportin
181
Would it be helpful to treat iron deficiency anemias with Epo?
- No. Iron deficiency anemia does not result from lack of Epo. Epo is already sufficient.
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55 yo male presents to clinic with symptoms, signs and initial workup suggestive of iron deficiency anemia. What do you first suspect?
- GI malignancy until proven otherwise. This applies to patients > 50 yo.
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Differential diagnosis for iron deficiency anemia
- Inflammatory bowel disease
- Ulcer/esophagitis
- Vascular malformations
- Hematoma, sequestration (rare) – example: closed fracture
- Gynecologic loss
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Signs and symptoms of iron deficiency
- Pica/pagophagia
- RLS
- Pallor/pale palmar crease/pale conjunctiva
- Glossitis
- Nail changes
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Tx of iron deficiency anemia
- Find bleeding, stop
- Replace blood (fluid if in shock; blood if significant end-organ compromised seen with Card-Pulm symptoms, renal insufficiency; give iron (enterally and parenterally))
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How does chronic disease lead to anemia?
- Hepcidin = acute phase reactant. Antibacterial effect to starve Fe-dependent functions in certain bacteria. During inflammation (RA) and other processes (cancer), release of IL-6, TNF, IFN-alpha and gamma induce hepcidin leading to decrease Fe absorption.
187
Type of formation seen in RBCs on PBS with autoimmune diseases
- Rouleaux formation
188
What is anemia of renal disease?
- Usually a normochromic anemia. People with chronic renal disease, poorly functioning renal fibroblast = no EPO = no marrow erythropoiesis stimulation
189
Which beta-thalassemia is transfusion-dependent?
- Beta-0
190
Treatment of beta-thalassemia
- Therapeutic phlebotomy (overload of Fe in RES: spleen, liver, marrow)
- Transfusion, but must be careful not to exacerbate iron overload.
191
Phenotype from beta-thalassemia patient
- Marrow expansion leads to bone expansion (crew-cut on skull x-ray), extramedullary hematopoiesis (hepatosplenomegaly)…
192
What is sideroblastic anemia? Causes?
- Anemia d/t defect in heme synthesis in midst of sufficient / high Fe stores. Ringed sideroblasts produced in marrow, which are erythroblasts containing precipitated non-heme iron, which tends to concentrate in mitochondria and encircle nucleus.
- Note, may be normocytic
- Causes:
a. Congenital: XLSA, autosomal recessive (SLC25A38), ALA synthase deficiency
b. Acquired: primary (myelodysplastic syndrome: pre-malignant disorder in bone marrow), secondary (etoh abuse, drug induced – isoniazid, chloramphenicol, lead poisoning, Cu deficiency)
193
In what disorder are Pappenheimer bodies found?
- Sideroblastic anemia
194
Tx of sideroblastic anemias?
- Transfuse. Therapeutic phlebotomy to treat iron overload.
- Pyridoxine
- Marrow transplant
195
Lab findings for chronic disease (including renal) anemia. Hgb, MCV, smear, Fe, TIBC, sat% (transferrin), ferritin
- Hgb: low
- MCV: low or nml
- Smear: chronic dz (nml, microcytic, hypochromic), chronic renal (nml)
- Fe:
196
Lab findings for thalassemia. Hgb, MCV, smear, Fe, TIBC, sat% (transferrin), ferritin
- Hgb: low
- MCV: low
- Smear: target/microcytic/hypochromic
- Fe: nml/high
- TIBC: nml/high
- % sat (transferrin): 30-80
- Ferritin: 50-300
- Electrophoresis: beta-thalassemia is abnml
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Lab findings for sideroblastic anemia. Hgb, MCV, smear, Fe, TIBC, sat% (transferrin), ferritin
- Hgb: low
- MCV: variable
- Smear: variable
- Fe: nml/high
- TIBC: nml
- % sat (transferrin): 30-80
- Ferritin: 50-300
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Cases from Volker
Cases from Volker
199
What is polycythemia?
- High Hb and Hct
200
Is RBC count high or low in thalassemia?
- High
201
Criteria for anemia in males and females
-
202
Retic count calculation. What value indicates reticulocytosis?
- (RBC count x retic %)/100
| - if
203
Types of macrocytic anemia and causes
1. Megaloblastic: vit B12 deficiency and folate deficiency = most common, also drug-related
2. Non-megaloblastic: hypothyroidism, liver dz, alcoholism, myelodysplastic syndromes
204
Classification of aplastic anemia
- Normocytic, non-hemolytic
205
Drugs that can cause megaloblastic anemia
- Metformin, triamterene, TMP/sulfamethaxazole, valproic acid
206
Objective findings for anemia patient
- Tachycardia, tachypnea, weight loss, pale skin/MM, nail changes (koilonychias), systolic murmur (may be heard), vibratory sensory loss (if vit b12), jaundice
207
Lab/smear findings for megaloblastic anemia
- MCV > 100 fL
- Macroovalocytosis
- Hypersegmented neutrophils, neutrophils with 5-6 + lobes
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B12 vs folic acid site of absorption
- B12: terminal ileum
| - B9 (folate): proximal jejunum
209
Complications of folate vs B12 deficiency
- Folate: megaloblastic anemia, NTDs
- B12: megaloblastic anemia w/neurologic abnormalities (demyelination of posterior spinal cord = spastic ataxia and dementia)
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Which deficiency will show up quicker after a change to a poor diet lacking many nutrients: B12 or B9 (folate)?
- B9. Stores last 3-4 months. B12 stores last 3-4 years.
211
Which population have highest incidence of B12 deficiency? Which has highest prevalence?
- Women > 60 yo = highest incidence
| - Prevalence = highest in African and Asian countries
212
Causes of B12 deficiency? What is most common?
- Most common = pernicious anemia
- Vegan, malabsorption (gastrectomy, ZES, ileal dz, drugs (metformin, PPI), fish tapeworm)
- Rare: congenital TC II deficiency, congenital methylmalonic acidemia/aciduria, NO inhalation
213
Symptoms and PE findings in B12 deficient patient
- Symptoms: standard anemia findings + paresthesias, ataxia, change in mental status
- PE findings: decreased position and vibratory sense, disturbance of vision/taste/smell, Romberg’s sign, Babinski’s sign, neuropathy
214
Labs necessary to diagnose B12 deficiency anemia
- CBC (MCV high) and retic count (decreased)
- Low B12 level
- High serum methylmalonic acid and homocysteine levels
- Smear = macrocytic RBCs, anisocytosis, poikilocytosis and hypersegmented neutrophils
- Bone marrow = megaloblasts, erythroid platelets
215
Tx of B12 deficiency anemia
- Find cause
- Give B12 (SC/IM or SL/PO is can absorb)
- Monitor K+ as hypokalemia can occur
- Bone marrow normoblastic w/in 12 hours, reticulocytosis in 3-5 days, Hb normalizes in 2 months
216
Complications from B12 deficiency
- Demyelination of posterior spinal cord = spastic ataxia, dementia
- Infertility in men and women
- Cervical smear abnormalities
217
How to diagnose pernicious anemia?
- Parietal cell and IF antibody
- Serum gastrin high, serum pepsinogen low
- Gastric biopsy
218
Most common causes of folate deficiency?
- Inadequate intake: alcoholism, elderly
219
Drugs that can lead to folate deficiency?
- Methotrexate, TMP, Dilantin, OCPs
220
How to differentiate between B12 deficiency anemia and folate deficiency anemia clinically?
- No neurologic abnormalities in folate deficiency anemia. Note: folate deficiency in pregnancy = NTD, which won’t happen with B12 deficiency in pregnancy. Labs (see another flashcard)
221
How to diagnose a folate deficiency anemia?
- Low Hgb with macrocytosis
- Low serum and RBC folate
- Smear: hypersegmented neutrophils
- High homocysteine levels, normal methylmalonic acid
- Nml or low B12
222
How to treat folate deficiency anemia?
- Consume foods rich in folate (green leafy veg, nuts)
- Supplement folic acid
- Note: correction can take a few months
223
What is aplastic anemia? Causes (incl. most common).
- It is a bone marrow failure caused by suppression or injury to stem cells resulting in inability to produce mature blood cells of all cell lines (pancytopenia)
- Causes: most common = idiopathic autoimmune. SLE, congenital, drugs, toxins, post-viral hep, pregnancy, PNH
224
Symptoms and PE findings of aplastic anemia
- Symptoms: anemia findings, bacterial or fungal infections (d/t neutropenia), mucosal or skin petechiae (d/t thrombocytopenia)
- PE findings: pallor, petechiae, purpura, hepatosplenomegaly (when advanced).
225
Patient presents with symptoms quite consistent with aplastic anemia. This also includes lymphadenopathy and bone pain. Thoughts?
- These symptoms/signs should not be present with aplastic anemia. Diagnosis is likely cancer.
226
How to diagnose aplastic anemia?
- Pancytopenia (two cell lines may be decreased early, but will always include reticulocytopenia)
- RBC morphology nml on smear (normocytic anemia), but mild macrocytosis present
- Bone marrow biopsy: hypocellular
227
Tx of aplastic anemia
- Mild cases: supportive care (stop agent, isolate, stool softener to prevent bleeding, aggressively tx fever or infections, reduce blood loss incl OCPs for menstruating females, GFs for cell lines, transfuse)
- Severe cases: bone marrow transplant
228
What lab values will tell you the difference between B12 and B9 deficiency anemia?
- Low serum folate (only in folate deficiency)
| - High methylmalonic acid only in B12 deficiency
229
Define hemolytic anemia
- Destruction of RBCs exceeds ability of marrow to increase RBC production (less than 100 days)
230
Classification of hemolytic anemia
- Sites of destruction (intravascular or extravascular)
- Acquired or congenital
- Mechanism of damage
231
Clinical signs/symptoms of hemolytic anemia
- Symptoms: SOB, tired, pale, weakness
- PE: jaundice, +/- splenomegaly
- Findings: +/- gallstones
232
Diagnostic lab tests for hemolytic anemia
- Haptoglobin decreased (both intravascular and extravascular hemolysis)
- LDH elevated (both)
- Coombs pos
- Retic count elevated
- Indirect bili elevated
- Urine hemosiderin elevated (intravascular hemolysis)
233
Most common enzymatic defect that leads to hemolytic anemia?
- G6PD deficiency
234
Heinz bodies and bite cells are seen in what anemia
- hemolytic anemia d/t G6PD deficiency
235
Triggers for hemolysis in G6PD deficiency patients
- Infections, medications (anti-malarials, sulfa drugs, abx, antipyretics, anticonvulsants), fava beans
236
Enzymatic deficiencies that lead to hemolytic anemia
- G6PD deficiency (most common)
| - Pyruvate kinase deficiency (subject to hemolytic crisis without exposure to oxidative agents)
237
Peripheral smear with pyruvate kinase deficiency anemia
- None
238
Causes of hemolytic anemias
- Auto-immune hemolytic anemia
- Enzyme deficiencies (G6PD, pyruvate kinase)
- Hemiglobinopathies (SCA)
- RBC defects (hereditary spherocytosis and eliptocytosis)
239
What is wrong with the spleen in sickle cell anemia? What is the clinical implication of this?
- Nothing inherently wrong with it, but recurrent splenic infarcts d/t shape of RBCs = functional asplenia. Patients are at increased risk for infection from encapsulated organisms (strep, meningococcal, Haemophilus, hep B and influenza) & Salmonella
240
Clinical manifestations of sickle cell anemia
- Tissue infarcts
| - Recurrent infections from encapsulated organisms + Salmonella
241
Hereditary spherocytosis and eliptocytosis. What is it? Genetics? Prevalence in what population? Complications? Diagnosis and tx?
- Defect leading to loss of membrane flexibility in RBCs = chronic hemolysis.
- AD. Prevalent in N. European population
- Complications: cholelithiasis, splenomegaly
- Dx: osmotic fragility test
- Tx: folate supplementation, genetic counseling, splenectomy d/t increased risk for rupture d/t trauma and to prolong RBC survival
242
Tx for autoimmune hemolytic anemia
- Corticosteroids if warm antibodies (IgG reactive)
| - Steroids ineffective if cold antibodies (IgM reactive). Tx here = warm environment, underlying cause (see flash card).
243
Which antibodies react with RBC membrane proteins in autoimmune hemolytic anemia? Antibodies to polysaccharides?
- Membrane: IgG. Best reaction at body temp (“warm antibodies”). Coombs pos.
- Polysaccharides: IgM. Best reaction at room temp (“cold antibodies”). Coombs neg.
244
What are the disorders associated with “cold” Ab autoimmune hemolytic anemia?
- Lymphoproliferative disorders, mycoplasma pneumonia, infectious mononucleosis, syphilis
245
Drugs associated with hemolytic anemias
- Penicillins
| - Quinine, methyldopa, certain cephalosporin abxs
246
Do cases from anemia II lecture
Do it
247
Define hemostasis
- Preventing blood loss at sites of injury whilst maintaining the fluid state of circulating blood. Balance bw excessive bleeding and hypercoagulability.
248
Briefest explanation of hemostasis
- Injury, release of factors including endothelin = vasoconstriction = reduced blood flow to area, ECM exposed d/t damage, platelets adhere and activate forming hemostatic plug (loose), tissue factor exposed sets motion of coagulation cascade resulting in activation of thrombin, thrombin cleaves fibrinogen to fibrin (strong), counterregulatory mechanism limit spread of clot.
249
Describe how platelets adhere to the extracellular matrix exposed at a site of vascular injury.
- ECs produce and secrete vWF into ECM, which is exposed with damage.
- Platelet adhesion: vWF interacts with GP1b on platelets linking them to collagen.
- vWF binds factor VIII (coagulation factor), which prolongs half-life
250
Function of vWF in normal function of VIII
- Localizes factor VIII appropriately and prolongs its half-life.
251
What is the role of von Willebrand factor and glycoprotein Ib (GPIb)?
- vWF links ECM collagen to GP1b on platelets after vascular damage exposes the ECM
252
Describe the morphological changes that occur upon platelet activation. What sorts of compound are secreted by activated platelets?
- Platelets when dormant are a flat pancake structure. When activated, they become spiny with long extension processes.
- vWF-GP1b interaction and integrin a2b1 binds collagen. Adhesion of platelet causes activation and Ca2+ signaling occurs. Platelets, now active, release secretory granules from
- a.) Dense (delta) granules: ADP, ATP, Ca2+, histamine, serotonin, epi
- b.) Alpha-granules: fibrinogen, fibronectin, vWF, factor V, PDGF and…
- Also releases free AA, converted to PG2 and gives rise to TXA2. With epi and serotonin = vasoconstriction
253
Function of AA secreted by activated platelets
- Converted to PG2, gives rise to TXA2. With epi and serotonin act as vasoconstrictors.
- Also, with ADP, stimulates further activation of more platelets.
254
Explain the process of platelet aggregation, including the necessary players.
- Initial clot adhesion is not sufficient to form a plug / clot.
- After initial activation, ADP and TXA2 also act in feed-forward activation, further stimulating activation of more platelets in vicinity.
- ADP triggers conformational change of GPIIb-GPIIIa in platelet membrane, which allows receptor to bind fibrinogen. Aggregation of platelets occur = plug.
255
Von Willebrand dz. Pathophys? Presentation? Management?
- Lowered/reduced vWF protein function and reduced factor VIII, therefore reduced binding platelets at damaged vascular sites.
- Most common inherited bleeding disorder. Identified usually in childhood with frequent epistaxis, excessive bleeding and bruising
- Management: desmopressin, which induces release of vWF and factor VIII from storage site in ECs.
256
What is the most common inherited bleeding disorder?
- Von Willebrand dz
257
Bernard-Soulier syndrome. Pathophys? Presentation? Management?
- Inherited dz. Giant platelets are present (unknown why), which fail to aggregate in response to stimuli d/t defect in interaction between vWF and GP1b
- Bleeding disorder
- Tx to reduce bleeding risk. Transfuse with platelets when bleeding or before surgery.
258
Glanzmann thrombasthenia. Pathophys? Presentation? Management?
- Inherited dz. Quantitative and qualitative defects in GPIIb and/or GPIIIa. Platelets fail to aggregate in response to stimuli.
- Bleeding disorder.
- Tx to reduce bleeding risk. Transfuse with platelets to address bleeding episodes.
259
What is the ultimate goal of the coagulation cascade?
- Activation of thrombin protease
260
Intrinsic pathway time is measured through what test?
- PTT (partial thromboplastin time test)
261
Extrinsic pathway time is measured through what test?
- PT (prothrombin time test)
262
What factor do the intrinsic and extrinsic pathways converge on?
- Factor X
263
What is the importance of vitamin K in the coagulation cascade? How does warfarin function in the prevention of blood clotting?
- 1972 (10, 9, 7 and 2 (prothrombin)) all contain gamma-carboxyglutamate residues to chelate Ca2+. This Ca2+ coordinates negatively charged membrane lipids and restricts clot formation to site of injury.
- The carboxylase that converts regulate glutamate to the carboxyglutamate on these factors requires vit K. Vit K must be regenerated through vit K epoxide reductase after this reaction runs.
- Warfarin is anticoagulant and prevents regeneration of vitamin K (procoagulant) through inhibition of the reductase, therefore acting as an anticoagulant.
264
Extrinsic pathway tenase complex
- TF+VIIa+X and Ca2+.
- This results in slow cleavage of prothrombin into thrombin. Prothrombin activates factor V with Ca2+ forming the prothrombinase complex forming large quantities of active thrombin.
265
Intrinsic pathway tenase complex
- IXa+X+VIIIa = rapid activation of factor X and rapid activation of thrombin
266
Describe how the prothrombinase complex generates active thrombin.
- Prothrombinase complex = prothrombin + Ca2+ + Xa + Va. This cleaves prothrombin rapidly forming large quantities of thrombin.
267
What are the roles of thrombin?
- Key regulator of hemostasis
- Cleaves soluble fibrinogen generating insoluble fibrin forming the soft fibrin clot (later cross-linked)
- Activates factors V and VII to sustain and accelerate the intrinsic pathway.
- Mediates conversion of factor XIII to factor XIIIA, transglutaminase (protein glue) forming bonds between lysine and glutamine in fibrin monomers = cross-linked hard clot.
- Also induces platelet aggregation and activates endothelial cells
268
What is the most common hemophilia?
- Hemophilia A (1/5000 male births) – XR
| - Less = B (1/30K) – XR
269
Hemophilia A. Pathophysiology? Tx?
- XR bleeding disorder, most common of hemophilias. Deficiency in factor VIII. VIII binds vWF. Also thrombin activates it and it forms part of the intrinsic tenase complex to rapidly activate factor X to activate thrombin.
- Tx = recombinant factor VIII, previously transfusion
270
Hemophilia B. Pathophysiology? Tx?
- XR bleeding disorder, least common of hemophilias. Deficiency in factor IX. IXa is part of the intrinsic tenase complex to rapidly activate factor X to activate thrombin.
- Tx = recombinant factor IX, previously transfusion
271
Describe the endogenous anticoagulation pathway.
- Thrombomodulin is present in the endothelial cell membranes.
- Thrombin binds thrombomodulin activates protein C.
- Protein C binds to S and together they block/degrade factors Va and VIIIa to block clotting.
272
What is ‘factor V Leiden’ and what are the consequences for patients?
- Defect: arg replaced with glutamine, generates factor V that is resistant to protein C cleavage. This leads to hypercoagulable state with increased risk for thrombosis. If heterozygote, 5 x increased risk. If homo, 50 x increased risk.
273
What is meant by the terms ‘serpins’ and ‘tissue factor pathway inhibitor (TFPI)? Function?
- Family of SERine Protease INhibitors. Example = AT III (antithrombin III), which inhibits thrombin and binds heparin. Also inhibits other complexes.
- TFPI (tissue factor pathway inhibitor) is produced by endothelial cells. It functions as inhibitor of factor VIIa to block extrinsic pathway. Also inhibits factor Xa.
274
How is fibrinolysis achieved?
- Plasminogen floats in plasma. It is converted to active plasmin by tPA (release of this is activated by protein C – see anticoagulation cascade) secreted by endothelial cells.
- Plasmin and tPA has high affinity for fibrin. Plasmin at this location degrades fibrin. tPA present to cleave any more plasminogen to active plasmin. If tPA release into circulation, it is inhibited by alpha-2 antiplasmin and a2-macroglobulin.
275
What is streptokinase and how does it function?
- Exogenous activator of plasminogen used to tx PE and DVT. May be given prophylactically post MI.
276
Define thrombosis.
Pathological process of blood clotting in uninjured vessel or an exaggerated blood clotting response to minimal injury.
277
What’s a mural thrombi?
Thrombi attached to the underlying vessel. This is usually how they are.
278
What is Virchow’s Triangle?
1. Endothelial Injury
2. Blood stasis or turbulence of blood flow.
3. Blood hypercoagulability.
279
What is the difference between arterial and venous thrombi?
Arterial and cardiac thrombi occur at site of endothelial injury or turbulence of flow. Venous thrombi occur at areas of blood stasis. Arterial thrombi grow back to the heart. Venous thrombi grow toward the heart.
280
Describe the pro-thrombotic properties of the endothelium.
Von Willebrand factor: enhances binding of platelets to ECM.
Tissue factor: produced by endothelium, activates extrinsic clotting pathway.
Plasminogen activator inhibitors (PAI): critical regulator of the fibrinolytic system.
281
Describe the anti-thrombotic properties of the endothelium.
Anti-platelet effect: non-activated platelets do not adhere to the endothelium; PGI2 + NO prevent platelet adhesion.
Anticoagulant properties: heparin-like molecule activate anti-thrombin III; thrombomodulin binds thrombin which activate protein C (anticoagulant)
Fibrinolytic properties: endothelium synthesizes t-PA (fibrinolysis)
282
Describe the contents of the alpha and delta granules of platelets.
Alpha granules: P-selectin, fibrinogen, fibronectin, factor V, factor VIII, PDGF, TGF-alpha.
Delta granules: ATP, ADP, Ca, histamine, epinephrine.
283
Explain the reaction of platelets on encountering ECM.
Adhere to ECM (collagen), mediated by vWF. Secrete granules.
Aggregate: form primary hemostatic plug (reversible). Platelet contraction then occurs (with the action of thrombin) – making plug irreversible. Then named secondary hemostatic plug.
284
Explain the consequences of endothelial injury and conditions/histories that contribute.
Endothelial injury is an important factor in arterial thrombosis; loss of endothelium will expose ECM and hence activation of platelets and thrombosis.
MI, ulcerated atherosclerosis, trauma, inflammatory disease of vessels.
Endothelial dysfunction is predisposing factor for thrombosis. HTN, bacterial endotoxins, hypercholesterolemia, radiation, smoking.
285
What is the role of blood stasis and turbulence of flow in thrombosis?
Turbulence enhances endothelial injury. Stasis enhances venous thrombosis.
Both result in platelets coming close to endothelium, accumulation of clotting factors, preventing clotting factor inhibitors, and endothelial activation.
286
Give medical conditions that contribute to blood stasis & turbulence of flow.
AA, MI, valve stenosis, rheumatic heart dz, hyperviscosity, Sickle cell dz.
287
What are primary and secondary reasons for hypercoagulability?
Primary (genetic): Factor V Leiden mutation, antithrombin III deficiency, Protein C deficiency, Protein S deficiency, Prothrombin G202010A gene mutation.
Secondary: anti-phospholipid syndrome, Lupus anticoagulant, prolonged immobilization, cancer, nephrotic syndrome, contraceptive pills, smoking.
288
What is heparin-induced thrombocytopenia?
Occurs during heparin therapy. Antibodies bind to platelets and activate them.
289
What is Antiphospholipid syndrome?
Antibodies to phospholipid (Cardiolipin). IN-vitro inhibits coagulation but in vivo induces coagulation.
290
What is Lupus anticoagulant?
Same as antiphospholipid syndrome.
291
Explain the difference between superficial and deep vein thrombosis.
Superficial: saphenous vein, local congestion + edema/swelling + pain/tenderness + ischemia + risk of infection. Rarely embolize.
DVT: popliteal, femoral, iliac veins, Can embolize. Presence of collaterals decreases signs of congestion and edema. Only 50% are asymptomatic.
292
What is disseminated intravascular coagulation?
Sudden widespread fibrin thrombi in the microcirculation. Occurs in shock, infection, pregnancy and with malignancy.
Leads to circulatory insufficiency (brain, lungs, heart, and kidneys). Leads to consumption of platelets and clotting factors and risk of bleeding.
293
What are the fates of a thrombus?
1. Propagation (progression). 2. Embolization. 3. Lysis. 4. Organization and recanalization (inflammation and fibrosis).
294
Difference between ischemia and infarction?
Ischemia = lack of oxygen, reversible. Infarction = tissue necrosis (irreversible).
295
What is the most common cause of preventable hospital death?
PE
296
What is the second most common medical complication?
Post-op VTE
297
Describe the stages of pulmonary thromboembolism and the difference between small, medium, large and massive.
Small: silent due to collateral bronchial artery flow. Organization with cumulative damage (idiopathic pulmonary HTN).
Medium: pulmonary infarct with acute respiratory and cardiac symptoms.
Large: RHF and collapse. (>60% pulmonary circulation)
Massive: sudden death, e.g. saddle embolus.
298
Characteristics/statistics of pulmonary thromboembolism?
20-25/100,000 hospital patients. 95% come from DVT above knee. May occlude main pulmonary artery (saddle embolus) or in small branches of vessels (multiple).
299
What is a paradoxical embolus?
Cardiac embolus passing to the right side through septal defect.
300
Define infarction.
Ischemic necrosis caused by occlusion of arterial or venous vessels. 99% due to thrombosis, mostly arterial.
MI, cerebral infarction, pulmonary infarction, bowel infarct, gangrene.
301
In which organs can you expect to see venous infarct?
Organs with single venous outflow: testis, ovary.
302
Which tissues are most vulnerable to hypoxia?
Neuron: 3-4 minutes, heart: 20-30 minutes, fibrous tissue: hours.
303
Factors influencing developing of infarct?
1. Nature of blood supply. Dual: lung, liver, hands; end-arterial: spleen, kidney.
2. Rate of occlusion: E.g. Atherosclerosis of coronary arteries is gradual slow process.
304
What clinical syndromes increase risk of thrombosis?
Antithrombin deficiency, protein C deficiency, protein S deficiency, activated protein C resistance, factor V Leiden, Factor VIII, prothrombin 20210, Lipoprotein A, lupus-like anticoagulant/anticardiolipin antibody.
MTHFR to homocysteine ratio was thought to increase risk for clotting but no longer thought to do so. Rather, alterations to homocysteine level is still considered a risk.
305
Describe the genotype and relative risk of FV Leiden Gene mutation.
Normal: RR =1.
Heterozygous: RR =7.
Homozygous: RR = 80.
306
What is the connection between Factor V Leiden, hormones and VTE?
3. 78 RR of VTE on just OCPs.
34. 7 RR of VTE with FV Leiden carrier + taking OCP.
6. 9 RR if only FV Leiden carrier.
307
When would you “further evaluate” clotting disorders and what would you check?
Young patient, family history, thrombosis in absence of known risks, recurrent miscarriages, warfarin-induced necrosis, neonatal purpura fulminans.
FV Leiden, Prothrombin 20210, homocysteine, Lipoprotein A, Factor VIII and VWF levels, PAI-1, Heparin cofactor2, Plasminogen.
308
Common inherited thrombophilias?
Defects in physiologic anticoagulant pathways:
Antithrombin deficiency.
Protein C deficiency.
Protein S deficiency.
Factor V Leiden.
Increased production of pro-coagulant:
Prothrombin G20210A gene mutation.
309
Clinical features of AT, PC, PS and APC-resistance?
Venous thrombosis (>90%) – DVT lower limbs and PE (common); superficial thrombophlebitis; mesenteric vein thrombosis ad cerebral vein thrombosis (rare).
Frequency fmhx thrombosis, first thrombosis at young age (
310
Describe characteristics of AT(III) deficiency.
Autosomal dominant. Quantitative and qualitative defects. Thrombotic phenomena in adolescence or even earlier. Frequently pulmonary embolism as first clinical manifestation.
311
Describe characteristics of PC deficiency and PS deficiency.
(SAME) Autosomal dominant. Quantitative and qualitative defects. Homozygotes die of thrombosis in utero or early infancy. Thrombotic phenomena in adolescence. Skin necrosis when warfarin therapy introduced.
312
Describe characteristics of Factor V Leiden deficiency.
Missense mutation changes arginine to glycine. Mutation is at preferred protein C cleavage site – slows inactivation of Factor Va by protein C. Single mutation responsible for almost all cases.
Factor Va procoagulant activity not affected.
Very common (up to 5% population are heterozygous). Accounts for up to 50% of inherited thrombophilia.
313
Prothrombin G20210A Mutation.
Mutation on 3’ non-coding prothrombin gene. No effect on structure or function.
Heterozygotes have 5-10% higher plasma levels of prothrombin and 2-3x risk of VTE.
1-2% population are heterozygotes; 5-7% young patients with DVT/PE.
314
Therapeutic options for thrombosis?
Unfractionated heparin, low molecular weight heparins, thrombolysis, Coumadin, ASA, PGP IIb/IIIa inhibitors.
315
Overall risk of thrombosis?
Incidence of thrombosis in adults is 1:1000. In children is 0.7:100,000.
One pro-thrombotic condition increases the risk of thrombosis by a factor of 5-8.
Thrombosis is multifactorial. Need at least 2 risk factors (if not 3-4).
316
Define thrombocytopenia
- Platelet count
317
Function of GPIIb/IIIa receptors in platelets
- These receptors bind to fibrinogen resulting in the aggregation and activation of platelets.
318
Three underlying causes of thrombocytopenia
- Underproduction
a. Destruction of megakaryocytes: parvo B19 (esp in sickle cell patient), HCV, HIV, HBC, drugs (most common in this category), chemo/radiation.
b. Inadequate precursor elements: B12, folate, Fe, congenital syndromes
c. Marrow replacement: granulomatous dz, myelofibrosis, malignancies
- Destruction
a. Immune-mediated: ITP, HIT, post-transfusion purpura, meds (heparine, quinine, quinidine, beta-lactams, sulfonamides, valproic acid), antiphospholipid ab syndrome
b. Non-immune-mediated: DIC, TTP/HUS (d/t E.coli), HELLP syndrome, gestational thrombocytopenia, mechanical destruction (prosthetic valves, LVAD), localized intravascular coagulopathy
- Sequestration: any cause of splenomegaly
a. Portal HTN d/t cirrhosis caused by Etoh, NAFLD, chronic viral hep, drugs, hemochromatosis OR Budd-Chiari syndrome. Hereditary spherocytosis, CML, hairy cell leukemia or MALT lymphoma.
319
What is HIT (heparin-induced thrombocytopenia)?
- Immune-mediated destruction of platelets 5-14 days post-heparin exposure. Abs form in response to heparin and platelet-specific PF4 complex. Ab activates platelets through Fc gamma receptor.
- Platelet reduction mild or moderate. Most profound thrombocytopenia will have thrombotic events not bleeding.
320
How would you evaluate thrombocytopenia?
- Careful hx (HPI and complete ROS, meds, drugs, herbals, nutritional status and toxins) and PE (mucocutaneous exam, LA, splenomegaly)
- Lab eval: CBC w/diff, review of PBS, assess electrolytes/renal function/liver function and thyroid, measure PTINR and PTT, consider d-dimer, fibrinogen and antiplatelet abs
- Bone marrow biopsy: PSIS or sternum, reserved for: patients with multiple cell lines (2 or more) involved, >60 with isolated thrombocytopenia and in patients whom empiric therapy is unsuccessful
321
How would you manage thrombocytopenia? What is the goal of platelet transfusion?
- Transfusion, corticosteroids, IVIG, plasmapheresis, splenectomy
- Goal of transfusion: >20-30K (unlikely to spontaneously hemorrhage), >50K if bleeding or invasive procedure planned.
322
When is platelet transfusion not indicated or a bad idea?
- ITP and HIT. May accelerate platelet destruction.
323
When infusing with patient with 1 unit of platelets, how much rise would you expect to see in count?
- Increase of 5K per 1 unit
324
ML is a 64 yo male minister who presents with fatigue and progressive numbness in feet bilaterally. He takes no meds and has been in good health. Exam remarkable for pallor, angular cheilitis, and diminished sensation to light touch in his bilateral LEs in a stocking distribution. CBC: WBC 3.9, Hgb 6.2, HCT 18.8, platelets 76K.
a. What test to order next?
b. What is the cause of his thrombocytopenia?
c. Management
a. B12, folate, MMA, anti-parietal cell ab, anti-IF ab, upper endoscopy to rule out gastric adenocarcinoma
b. Pernicious anemia
c. B12 replacement SC
325
Besides megaloblastic anemia, what else can be seen in patients with pernicious anemia (megaloblastic) d/t B12 deficiency?
- Thrombocytopenia
326
What is pseudothrombocytopenia?
- Platelet aggregation or clumping d/t inadequate anticoagulation of specimen or presence of EDTA agglutinins from patient (0.1% of population). This happens when blood is collected with a purple top tube.
- Note: use blue top tube to r/o.
327
RC is a 26 yo female who presents to office c/o recent onset of rash and bleeding from her gums. Reports menorrhagia for 6 months, no constitutional complaints. She has been in good health before this and uses no illicit substances. Exam reveals diffuse mucocutaneous petechial rash. CBC: WBC 6.3, Hgb 12.6, HCT 38, platelets 11K.
a. What is her diagnosis?
a. ITP: immune/idiopathic thrombocytopenic purpura.
328
What is ITP? Clinical presentation? Diagnosis? Treatment?
- Accelerated destruction of platelets. Chronic dz of insidious onset in adults, more commonly female. Antiplatelet antibodies present binds to mostly GPIIb/IIIa. These platelets are coated and destroyed by spleen.
- Presentation: often asymptomatic, with severe to profound thrombocytopenia. May demonstrate: purpura, petechiae, epistaxis, bleeding gums, menorrhagia, GI/GU bleeding and ICH are rare.
- Commonly diagnosis of exclusion. Based on clinical presentation.
- Tx: observe, IV corticosteroids, IVIG, rituximab/mycophenolate, thrombopoetin analogues, splenectomy
329
62 yo homeless man with untreated HCV infection presents with fever and abdominal pain. PMHx: COPD, tobacco use and etoh abuse. On exam: jaundiced + sclera icterus, atrophy of proximal muscles, ascites, palmar erythema, caput medusa. CBC: WBC 14.6, Hgb 9.1, HCT 28, platelets 61K.
a. What is his diagnosis?
b. What is the cause of his thrombocytopenia?
a. Portal HTN secondary to HCV and etoh abuse
| b. Thrombocytopenia d/t splenic sequestration, nutritional deficiency and direct toxic effect of etoh on the marrow
330
If you suspect an underproduction issue leading to thrombocytopenia, what else is likely true?
- Unless inherited disorders, generally associated with decreased RBC and WBC production too.
331
Most common cause of thrombocytopenia d/t underproduction is?
- Drugs
