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Flashcards in Pathology-Red Cell Disorders Pathology Deck (126):
1

What are hypoxic symptoms that present in patients with anemia?

Weakness, fatigue, dyspnea, pale conjunctiva & skin, headache, lightheadedness and angina.

2

What is a situation where a patient would have an abnormal Hb, Hct and not be truly anemic?

Pregnancy. More blood volume = diluted RBC concentration.

3

What is a situation where a patient would have a normal Hb, Hct but actually be anemic?

Bleeding out from a gunshot wound. RBC concentration remains the same, but total blood volume is decreased. Hct and Hgb will show anemia once fluid loss has been replaced.

4

Lab definition of anemia>

Hb < 13.5g/dL in males. < 12.5g/dL in females.

5

What defines normocytic anemia?

MCV = 80-100. < 80 = microcytic anemia. > 100 = macrocytic anemia.

6

What is responsible for the RBCs being small in microcytic anemia?

RBC generation starts with a large erythroblast. The erythroblast divides into smaller cells until the RBC has the desired concentration of Hb. When there is decreased production of Hb, the RBC divides again to maintain the correct concentration, thus creating a smaller RBC.

7

What is hemoglobin?

Heme (Fe2+ & Protoporphyrin) + Globin.

8

How can Fe2+ cause a microcytic anemia?

Nutritional Fe2+ deficiency = less heme = less Hgb = more RBC divisions to maintain proper Hgb concentration. Chronic inflammatory state = Fe2+ locked away in macrophages = less heme = less Hgb = more RBC divisions to maintain proper Hgb concentration.

9

How can protoporphyrin cause a microcytic anemia?

Sideroblastic anemia = low protoporphyrin levels = less heme = less Hgb = more RBC divisions to maintain proper Hgb concentration.

10

How can globin cause microcytic anemia?

Thalassemia = decreased production of the globin chain = decreased Hgb = more RBC divisions to maintain proper Hgb concentration.

11

What type of iron is more readily absorbed in the duodenum?

Heme iron (meat derived).

12

How is iron absorbed by the intestines and put into the blood?

Enterocyte absorbs Fe from gut lumen -> Ferroportin transports Fe from enterocyte to blood -> Transferrin transports Fe in blood to liver and bone marrow macrophages -> Fe is stored intracellularly by bound ferritin.

13

What 4 laboratory tests should you use to consider the iron status of a patient?

How much iron is in blood = serum iron, how many transferrin molecules are in the blood = TIBC,  how many transferrin molecules are bound by iron = % saturation, how much iron is stored in bone marrow macrophages and liver = serum ferritin

14

What are common causes of anemia in infants? Children? Adult men? Adult women? Elderly in Western world? Elderly in 3rd world?

Infants: breast feeding (no Fe in breast milk); Children: poor diet; Adult men: peptic ulcer disease; Adult women: menorrhagia or pregnancy; Elderly: colon polyps/ colon carcinoma in Western world, hookworm (Necator and Ancylostoma)

15

Why are celiac patients at risk for Fe-deficiency anemia?

Destruction of the duodenal villi caused malabsorption of iron.

16

Why are patients with a gastrectomy at risk for Fe-deficiency anemia?

Stomach acid maintains the Fe2+ state and it is more readily absorbed. Decreased acid in patients with a gastrectomy have more Fe3+ that is not as readily absorbed.

17

What are the stages of iron deficiency anemia?

1) Body depletes stored iron = decreased serum ferritin, increased TIBC. 2) Serum iron is depleted = serum iron decreases, % saturation decreases. 3) Bone marrow recognizes there is less iron = makes fewer RBCs = Normocytic anemia. 4) Bone marrow pumps out smaller cells w/less Hgb = Microcytic and hypochromic (increased central area of pallor) anemia.

18

What happens to TIBC when ferritin goes down?

It goes up. This makes sense because depletion of storage iron (serum ferritin) causes the liver to send out more transferrin to look for more iron to bring back from the blood (TIBC)

19

What is the normal % saturation?

Typically 1/3 transferrin molecules are bound by Fe, so 33%. This goes down when you are anemic because now maybe 1/6 are bound by iron.

20

What is the early stage of iron deficiency anemia?

Normocytic anemia

21

What are the clinical features of iron-deficiency anemia?

1) Anemia 2) Koilonychia (spoon-shaped nails) 3) Pica (chewing on things like dirt or ice)

22

Why do you see an increased RDW in iron-deficiency anemia?

The anemia starts with a normocytic anemia and progresses to a microcytic anemia. This creates a population of RBCs that vary widely in their sizes.

23

What lab value changes would you expect to see in a patient with iron deficiency anemia? Peripheral blood smear, MCV, RDW, ferritin, TIBC, serum iron, % saturation & FEP?

Peripheral blood: hypochromic RBCs, MCV: decreased, RDW: increased, ferritin: decreased, TIBC: increased, serum iron: decreased, % saturation: decreased, FEP: 

24

What lab value will be elevated as a direct result of Fe-deficiency and inability to form heme?

Free Erythrocyte Protoporphyrin (FEP). Note that heme consists of protoporphyrin and iron. If there is not enough iron to make heme, there will be increased free erythrocyte protoporphyrin.

25

What about this blood smear makes you think this patient has iron-deficiency anemia?

Microcytic (many RBCs that are actually smaller than a lymphocyte’s nucleus) and hypochromic anemia.

26

How do you treat iron-deficiency anemia?

Supplemental iron (ferrous sulfate) and uncover the underlying cause of anemia and treat if possible.

27

A patient presents with anemia, dysphagia and a beefy red tongue. Why does this patient have dysphagia?

The patient has the classic triad of Plummer-Vinson syndrome: anemia, an esophageal web (causing dysphagia) and atrophic glossitis.

28

What is the most prevalent type of anemia you will see in hospitals? How does this happen?

Microcytic anemia of chronic disease. Chronic disease results in release of the acute phase reactant, hepcidin. Hepcidin locks iron in its storage sites away from bacteria to prevent replication. Preventing Fe release from macrophages to erythroid precursors causes microcytic anemia. Hepcidin also suppresses EPO production.

29

A patient in the hospital is battling an invasive brain tumor. He is not losing any blood from the tumor, but is anemic. What would you expect to see on lab values: ferritin, TIBC, serum iron, % saturation and FEP?

This patient most likely has anemia of chronic disease from release of hepcidin. Ferritin levels will increase because hepcidin prevents Fe release from macrophages. TIBC will decrease because storage levels are high. Serum iron will decrease because it will be depleted and hepcidin inhibits Fe release. % saturation will be decreased because there is less serum iron available to bind to transferrin. FEP will increase because there is less iron available to pair with protoporphyrin and form heme.

30

A patient in the hospital is battling an invasive brain tumor. He is not losing any blood from the tumor, but is anemic. Ferritin is increased, TIBC is decreased, serum iron is decreased, % saturation is decreased and FEP is increased. How do you treat this patient?

1) Treat the underlying cause to get hepcidin out of the picture and free stored iron for usage 2) Administration of exogenous EPO in especially helpful in patients with cancer.

31

What enzyme is responsible for the final step in heme synthesis?

Ferrochelatase combines Fe2+ with protoporphyrin in the mitochondria of the erythroid precursor.

32

What is the rate limiting step in the production of protoporphyrin? How is this clinically relevant?

Succinyl CoA -> ALA by the enzyme ALAS (ALA synthase). This is clinically significant because the reaction can be impaired if someone has B6 deficiency.

33

What reaction follows the conversion of succinyl CoA to ALA by the enzyme ALAS?

ALA -> porphobiliinogen by the enzyme ALAD (ALA dehydrogenase)

34

Where does iron go after it is release from the bone marrow macrophages in its quest to form heme? What happens if the patient has sideroblastic anemia?

The mitochondria of the erythroid precusor. There it meets up with protoporphyrin and forms heme. If the patient has sideroblastic anemia, there is no protoporphyrin in the mitochondria for Fe to react with. The mitochondria become iron-laiden and form a ring around the nucleus of the erythroid precursor (forming a ringed sideroblast).

35

What is the most common cause of congenital sideroblastic anemia?

The rate-limiting enzyme of protoporphyrin synthesis: ALAS. This is the enzyme that catalyzes the reaction succinyl CoA -> ALA.

36

What are common causes of acquired sideroblastic anemia?

ALCOHOLISM: mitochondrial poison that damages production of protoporphyrin. LEAD POISONING: lead can denature the enzymes ALAD (ALA -> porphobiliinogen) and ferrochelotase (Fe + protoporphyrin -> heme). B6 DEFICIENCY: succinyl CoA -> ALA by the enzyme ALAS requires vitamin B6.

37

When do patients typically present with a sideroblastic anemia from B6 deficiency?

Isoniazid therapy

38

A patient presents who is anemic. He works at a pistol range cleaning up shells and has been there over 30 years. Peripheral blood smear shows ringed sideroblasts. What would you expect to see on labs ferritin, TIBC, serum iron and % saturation?

Sideroblastic Anemia generally presents in an iron-overloaded state because iron-laiden erythroid precursors die and iron leaks out of the cell. Bone marrow macrophages eat the leaked iron = increased ferritin and decreased TIBC. Iron leaks into blood = increased serum iron and increased % saturation. Note that hemochromatosis will share similar laboratory findings.

39

What is the difference between a thalassemia and sickle cell anemia?

Thalassemias arise from decreased synthesis of globin chains. Sickle cell anemia has normal globin synthesis, but the globin chain is mutated.

40

What disease are carriers of inherited thalassemia, sickle cell mutations and people with G6PD deficiency protected from?

Plasmodium falciparum malaria

41

What are the normal types of hemoglobin found in the human body?

HbF (fetal) : alpha2gamm2. HbA: alpha2beta2. HbB: alpha2delta2. Note that the alpha chain is used by each hemoglobin.

42

Why does a single deletion on the locus for the alpha hemoglobin chain not cause thalassemia? What does it take for someone to become symptomatic with alpha-thalassemia?

There are 4 alpha alleles on chromosome 16 (2 on each chromosome). People become mildly anemic with alpha-thalassemia when 2 genes are deleted.

43

Why is thalassemia not as bad in African compared to Asia?

The cis 2 gene deletion is more common in Asia, which is the more severe deletion. The trans 2 gene deletion is more common in Africa.

44

A mother has a child with severe anemia. There were no symptoms of anemia during pregnancy. Hgb electrophoresis reveals HbH. What is causing the baby’s anemia?

3 alpha hemoglobin genes have been deleted. In utero, the baby was utilizing HbF, where the single alpha gene was sufficient to have normal Hgb. When the child was born, decreased alpha chain causes beta chain tetramers to form, which are HbH. These tetramers damage RBCs and cause anemia.

45

An asian couple comes to the clinic because of infertility problems. The wife has had multiple miscarriages and is currently a few weeks pregnant. What test do you want to do on fetal blood?

Electrophoresis for Hb Barts. Asians are prone to have the cis 2 gene deletion. If each parent gives a chromosome with 2 cis gene deletions on each chromosome the child will have 4 genes deleted, which is lethal and called hydrops fetalis. It is lethal because the defect in alpha chains causes formation of gamma tetramers (Hb Barts) instead of HbF

46

Why are beta-thalassemia symptoms so much more variable than those of alpha-thalassmia?

Although there are only two beta genes on chromosome 11, there are 3 possibilities for each gene: normal beta chain, beta null (beta globin chain is absent) and beta + (diminished production of beta-globin chain). The combination of these makes for a wide spectrum of disease.

47

A 22 year old army recruit comes in for his blood work. He reports no symptoms of any illness. Labs reveal increased RBC count, microcytic anemia and peripheral blood smear is shown below. What genetic mutation is likely causing his condition?

Beta thalassemia minor (Beta/Beta +). Note the hypochromic cells and target cells in the peripheral blood smear. Target cells appear when there is decreased Hgb in the RBC cytoplasm, allowing for a bleb to protrude from the center of the RBC in the normal area of pallor. Note that this is the mildest form of beta-thalassemia and usually is asymptomatic.

48

A 22 year old army recruit comes in for his blood work. He reports no symptoms of any illness. Labs reveal increased RBC count, microcytic anemia and peripheral blood smear shows hypochromic cells and target cells. What is the key lab finding for this condition?

When people have beta thalassemia minor they present without symptoms and microcytic, hypochromic cells with target cells and an isolated increase in HbA2 on Hgb electrophoresis.

49

A mother has a 2 month old baby with severe anemia. There were no symptoms of anemia during pregnancy. Hgb electrophoresis reveals increased HbA2 & HbF and no HbA. What is causing the baby’s anemia?

The baby has beta-thalassemia major. This is from beta null/beta null mutations that presents with severe anemia after birth because in utero the child is utilizing HgF, which is composed of alpha2/gamma2 subunits, not using a single beta subunit. HgF is protective for a few months until the body begins to rely on alpha2/beta2 Hgb.

50

Why do babies with beta-thalassemia major develop massive erythroid hyperplasia?

The absence of beta subunits (beta null/beta null) causes alpha tetramers to form. These tetramers damage RBCs as they are being produced so you get ineffective erythropoiesis. The spleen also recognizes the alpha tetramers so you get extra vascular hemolysis of RBCs if they make it out of the marrow. This puts the marrow on overdrive for RBC production.

51

What clinical signs give you a high index of suspicion for beta-thalassemia major?

Severe anemia, “crew-cut” sign on x-ray from expansion of hematopoiesis into marrow of skull, a “chipmunk face” from expansion of hematopoiesis into the marrow of the facial bones and hepatosplenomegaly from extramedullary hematopoiesis.

52

A mother has a 2 month old baby with severe anemia. There were no symptoms of anemia during pregnancy. Hgb electrophoresis reveals increased HbA2 & HbF and no HbA. If you could vaccinate this kid against any organism, what would you pick?

This kid has beta-thalassemia major. He depends on every single red blood cell that gets made. If he were infected by parvovirus B19, which infects and shuts down erythroid precursors, he would experience aplastic crisis because he can’t risk erythropoiesis shut down for a day.

53

How do you treat people with beta-thalassemia? What is a complication of this?

Chronic transfusions are often necessary and can cause development of secondary hemochromatosis.

54

A mother has a 2 month old baby with severe anemia. There were no symptoms of anemia during pregnancy. Hgb electrophoresis reveals increased HbA2 & HbF and no HbA. What did you most likely see on labs before you ordered the electrophoresis?

Beta-thalssemia major presents with microcytic anemia, hypochromic targets cells and nucleated red blood cells (due to hematopoiesis in abnormal locations). Note that HbA2 (alpha2delta2) and HbF (alpha2gamma2) are increased because they don’t utilize the beta subunit and HbA is absent because it needs the beta subunit.

55

What are the most common causes of macrocytic anemia?

Folate and B12 deficiency. Deficiency in these substances results in decreased DNA precursor molecules. Less DNA precursors prevents the erythroid precursors from dividing one last time and you get larger than normal cells.

56

Why does folate deficiency go hand-in-hand with B12 deficiency when considering megaloblastic anemia?

When folate enters the body it is methylated. It can’t participate in formation of DNA precursor molecules until that methyl group is taken off by B12. Once B12 has the methyl group, homocysteine then takes it and is converted to methionine.

57

Why is anemia related to B12 and foliate deficiencies specifically referred to as megaloblastic anemias? What causes macrocytic anemias?

Deficiency in B12 and folate makes cells other than RBCs in the body that are dividing rapidly (enterocytes) large too. Alcoholism, liver disease and drugs (5-FU) can cause macrocytic anemias without megaloblastic non-RBC cells or hypersegmented neutrophils.

58

Aside from macrocytic RBCs, what else might give you a hint that a patent has megaloblastic anemia on a peripheral blood smear?

Hypersegmented neutrophils (5+ lobes).

59

How do you get folate into your body?

Eat green veggies and fruits and absorb it in the jejunum.

60

How long does it typically take to develop folate deficiency?

Months, we have very limited stores of folate in our bodies.

61

Name 3 ways you can become folate deficient?

1) Poor diet (alcoholics & elderly) 2) Increased demand for folate (pregnancy, cancer and hemolytic anemia) 3) Folate antagonists (methotrexate inhibits dihydrofolate reductase which results in a folate deficiency).

62

A 34 year old woman presents to the clinic complaining of fatigue and tongue pain. You do a blood draw and labs reveal a macrocytic anemia with hypersegmented neutrophils. Homocysteine levels are increased. What test will you do next to narrow your diagnosis?

She is presenting with symptoms consistent with megaloblastic anemia. Now you need to tell if its from folate deficiency, B12 deficiency or both by checking methylmalonic acid levels. B12 plays a key role in converting methylmalonic acid to succinyl CoA. Methylmalonic acid levels will be high in people with B12 deficiency and normal in people with folate deficiency. You could also measure serum folate and B12 levels directly.

63

How is B12 absorbed by our body?

When you eat meat, B12 is cleaved from animal proteins and R-binder in the saliva binds to B12. R-binder and B12 travel through the GI system and into the small bowel where R-binder is cleaved by pancreatic proteases. B12 then binds to intrinsic factor (IF is produced by the parietal cells in the body of the stomach) and is absorbed in the ileum.

64

Why does B12 deficiency take so long to develop?

There are very large stores of B12 in the liver.

65

What is the most common cause of B12 deficiency? What are other causes?

Pernicious anemia. This is a result of autoimmune destruction of parietal cells in the stomach and loss of IF, resulting in no B12 absorption in the ileum. Pancreatic insufficiency results in R-binder not being cleaved and IF not binding to B12. Damage to the ileum by Crohn’s or diphyllobothrium latum prevents absorption at the ileum. Finally, dietary deficiency, which is very rare except in vegans.

66

A 34 year old woman presents to the clinic complaining of fatigue and tongue pain. You do a blood draw and labs reveal a macrocytic anemia with hypersegmented neutrophils. Homocysteine levels are increased. What additional physical exam finding would make you think her symptoms are due to vitamin B12 deficiency?

Subacute combined degeneration of the spinal cord. This is because B12 is required to convert methymalonate to succinyl CoA. When B12 is deficient, methylmalonate builds up in the myelin in the posterior column of the spinal cord and damages neurons. Note that labs would differentiate this from folate deficiency by and increase in methylmalonic acid.

67

What is your next test to do if a patient has a normocytic anemia?

Reticulocyte count to determine if they are hyperproliferative or hypoproliferative. (Note the reticulocyte shown below with the bluish cytoplasm from residual RNA). If the corrected reticulocyte count > 3%, you know there is good marrow response and the problem is likely due to peripheral destruction. If the corrected reticulocyte count < 3%, you know the marrow is responding poorly and there is underproduction of red cells.

68

How does properly functioning bone marrow respond to anemia?

It increases the reticulocyte count to about 3% from 1-2%. Note that the count is normally around 1-2% because that is about how many erythrocytes are recycled from the blood each day.

69

Why is the reticulocyte count falsely elevated in anemia? How do you adjust for this?

In anemia, you lose RBCs. If reticulocytes remain the same, then they will make up a larger percentage of blood and be falsely elevated. You adjust for this by multiplying the reticulocyte percentage in blood by the patient’s hematocrit/45… the normal hematocrit.

70

A patient presents with normocytic anemia and a corrected reticulocyte count > 3%. What are two causes of the patient’s anemia?

1) Extravascular hemolysis by reticuloendothelial macrophages in the spleen, liver and lymph nodes. 2) Intravascular hemolysis of RBCs.

71

How do macrophages of the reticuloendothelial system break down hemoglobin in the RBCs?

Globin -> amino acids and is recycled. Heme -> iron (recycled) and protoporphyrin. Protoporphyrin -> unconjugated bilirubin -> unconjugated bilirubin bound to serum albumin and goes to liver for conjugation -> conjugated bilirubin put into the bile.

72

A patient presents with normocytic anemia and a corrected reticulocyte count > 3%. Physical exam reveals conjunctival pallor and splenomegaly. What other clinical and lab findings would you expect to see in this patient?

Extravascular hemolysis by reticuloendothelial macrophages causes patients to present with jaundice from unconjugated bilirubin, bilirubin gallstones and bone marrow hyperplasia.

73

A patient presents with normocytic anemia and a corrected reticulocyte count > 3%. Physical exam reveals conjunctival pallor and Coca-Cola colored urine. What other clinical and lab findings would you expect to see in this patient?

The hemoglobinuria tips you off that this patient has intravascular hemolysis going on. You would also find decreased serum haptoglobin because it is binding up free Hgb in the blood from lysed RBCs, hemoglobinemia and hemosiderinuria.

74

When do patients with anemia from intravascular hemolysis present with hemosiderinuria?

A few days later. When Hgb is filtered by the kidneys, Hbg is taken up by the tubular cells and broken down within the renal tubular cells. The Fe builds up in the tubular cells and presents as hemosiderinuria a few days later when the iron-laiden tubular cells slough off and come out in the urine.

75

A 20 year old man presents with splenomegaly, gallstones and jaundice. Labs reveal an increased unconjugated bilirubin, RDW and MCHC and normocytic anemia. Peripheral blood smear is shown below. Osmotic fragility test. What is causing this patient’s condition?

The patient has hereditary spherocytosis. This is due to inherited defect in cytoskeleton membrane tethering proteins: most commonly spectrin, ankyrin or band 3.1. Note the spherocytes with loss of central pallor, increased RDW from splenic macrophage consumption of RBC blebs, increased MCHC from increased RBC [Hgb] due to decreased cytoplasm, splenomegaly from hypertrophy of macrophages due to eating of spherocytes and jaundice from hemolysis.

76

Why do patients with hereditary spherocytosis commonly present with an elevated RDW?

The defect in cytoskeleton membrane tethering proteins causes blebs of membrane to form on the RBCs. These blebs are eaten by splenic macrophages every time they pass through, losing significant amount of membrane over time. Consequently, older spherocytes are smaller because they have lost more membrane and younger ones are larger.

77

What is responsible for the anemia seen in hereditary spherocytosis?

The spherocytes get so small and round that they cannot maneuver through the spleen and are eaten up by splenic macrophages.

78

A 20 year old man presents with splenomegaly, gallstones and jaundice. Labs reveal an increased unconjugated bilirubin, RDW and MCHC and normocytic anemia. Peripheral blood smear is shown below. Osmotic fragility test is positive. What condition would be life threatening to this patient?

Parvovirus B19 infection of erythroid precursors, resulting in aplastic crisis. This is because there is already limited production of RBCs by the bone marrow due to early termination of spherocytes. 

79

What is the diagnostic test for hereditary spherocytosis?

Osmotic fragility test. Normal RBCs can tolerate swelling from being in a hypotonic solution. Spherocytes do not have any extra membrane and burst more rapidly in a hypotonic solution.

80

A 20 year old man presents with splenomegaly, gallstones and jaundice. Labs reveal an increased unconjugated bilirubin, RDW and MCHC and normocytic anemic. Peripheral blood smear is shown below. Osmotic fragility test is positive. How do you treat this patient?

Splenectomy. Spherocytes will persist, but anemia will resolve because macrophages are no longer terminating them early in their lifecycle.

81

What do you know about this patient?

This is a Howell-Jolly body. This indicates that the patient has had a splenectomy because there is persistent DNA inside of the RBC that is normally removed by the splenic macrophages.

82

A mother brings in her 6 month old girl who has jaundice and chipmunk facies. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin and normocytic anemia. Peripheral blood smear is shown below. What is causing the child’s symptoms?

This patient has sickle cell anemia. This is an AR mutation in the beta chain of Hgb that replaces hydrophilic Glu with hydrophobic Val. In order to have sickle cell DISEASE, you must have 2 abnormal beta genes; this will result in > 90% HbS in RBCs.

83

How would you make sickle cell anemia symptoms worse?

HbS polymerizes when deoxygenated, so when patients are put under stress like hypoxemia, acidosis and dehydration the HbS polymers will aggregate into needle-like structures, resulting in sickle cells, and symptoms will worsen.

84

Why don’t people with sickle cell anemia present until after 6 months old? How does this apply to treatment of sickle cell disease?

For the first six months, HbF levels are high. HbF is protective against sickle cell anemia because it does not have the hydrophobic mutation to polymerize with other RBCs. This concept is utilized for treatment with hydroxyurea, which increases levels of HbF.

85

Why does having HbS make you anemic?

The cells undergo continuous sickling and desickling as the RBC is deoxygenated and oxygenated, respectively. This results in membrane damage that makes the cell less flexible and the spleen removes them from the circulation early in their lifecycle.

86

Jaundice and gallstones are signs of extravascular hemolysis in sickle cell disease. What are signs of intravascular hemolysis?

Decreased haptoglobin (molecule that scavenges lysed Hgb) and target cells on blood smear (from dehydration of RBC and central bleb arises).

87

Because of extravascular and intravascular hemolysis in sickle cell disease, you get massive erythroid hyperplasia. What are signs of this condition?

Expansion of hematopoiesis into skull (crew cut x-ray) and facial bones (chipmunk face) and hepatomegaly from extramedullary hematopoiesis.

88

A mother brings in her 6 month old girl who has jaundice and chipmunk facies. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin and normocytic anemia. Peripheral blood smear is shown below. What condition would pose a major threat to this child’s life?

Aplastic crisis with parvovirus B19 infection of erythroid precursors.

89

A mother brings in her 6 month old girl who has jaundice and chipmunk facies. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin and normocytic anemia. Peripheral blood smear is shown below. What physical exam finding would you expect to see if the child’s RBCs were undergoing irreversible sickling?

Vascular occlusion and infarction. The common presenting sign in infants is dactylitis: swollen hands and feet from vaso-occlusive infarcts of the bones.

90

A mother brings in her 6 month old girl who has jaundice and chipmunk facies. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin and normocytic anemia. Peripheral blood smear is shown below. What is the most common cause of death in children due to this condition?

Vascular occlusion and infarction from irreversible sickling of RBCs in sickle cell disease causes the spleen to become shrunken and fibrotic. Autosplenectomy increases risk of infection by encapsulated organisms (because it is main site of antibody production) and is the most common cause of death in children. There is also increased risk of salmonella paratyphi osteomyelitis.

91

A mother brings in her 6 month old girl who has jaundice and chipmunk facies. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin and normocytic anemia. The child has had multiple severe illnesses due to infection by encapsulated bacteria. What would you expect to see on peripheral blood smear in this patient?

Sickle cell disease results in autosplenectomy. In addition to sickle cells, you would also see Howell-Jolly bodies from autosplenectomy and residual DNA in RBCs due to decreased splenic macrophage function.

92

A 25 year old man comes to see you who has jaundice and chipmunk facies. He complains of chest pain and shortness of breath that has persisted since he had pneumonia a few days ago. Physical exam reveals hepatomegaly. Labs reveal elevated unconjugated bilirubin, normocytic anemia and pulmonary infiltrates. Peripheral blood smear is shown below. What is the most common cause of death in adults due to this condition? What other presentations are related to this?

The most common cause of death from sickle cell disease in adults is acute chest syndrome from vaso-occlusion of pulmonary microcirculation. Vaso-occlusion of bone can also cause pain crisis, vaso-occlusion of renal arteries causes renal papillary necrosis (presents with gross hematuria and proteinuria).

93

Why can people with sickle cell trait still join the military?

Sickle cell trait is an abnormal beta chain in only one of two genes. The normal gene produces HbA more efficiently that the abnormal gene produces HbS; consequently there will be less than 50% HbS in the blood, which prevents sickling of RBCs and limits symptoms.

94

Although people with sickle cell trait are largely asymptomatic, what things should they be on the lookout for?

Extreme hypoxia and hypertonicity causes sickling. This would result in microinfarctions in the renal medulla, microscopic hematuria and decreased ability to concentrate the urine.

95

What lab test tells you if the patient has sickle cell disease and if the patient has sickle cell trait?

Normally sickle cells and target cells are only seen in sickle cell disease, and not in sickle cell trait. If you treat the blood sample with metabisulfite, any HbS RBCs will sickle, whether they have the disease or the trait.

96

How does Hb electrophoresis differ in sickle cell disease vs. sickle cell trait?

*

97

A patient presents with a mild normocytic anemia. Peripheral blood smear is shown below. What is your diagnosis?

Note the Hgb C crystal, the patient has Hemoglobin C. This is an AR mutation in the beta chain of hemoglobin that replaces Glu with Lys. Note that this is less common than sickle cell disease.

98

How do RBCs protect themselves from being destroyed be complement?

Decay accelerating factor (DAF accelerates decay of C3 convertase) and Membrane inhibitor of reactive lysis (MIRL) are both connected to the RBC membrane by GPI anchoring protein. Both of these inactivate complement.

99

A 24 year old man presents with fatigue, shortness of breath and chest palpitations. He also says that his urine is dark colored when he wakes up in the morning. He has a history of multiple DVTs. Labs reveal microcytic anemia, decreased serum iron, decreased serum ferritin, increased TIBC, % saturation is decreased and RDW is increased. What is causing this patient’s symptoms?

This patient has paroxysmal nocturnal hemoglobinuria. This is an acquired defect in some of the myeloid stem cells where GPI is absent. Consequently DAF and MIRL are absent and RBCs, platelets and WBCs are hemolyzed by complement. This happens at night because breathing shallow during sleep = CO2 is retained = you go into respiratory acidosis = activates complement = intravascular RBC hemolysis and very dark urine in the morning. Note that his labs show iron-deficiency anemia from loss of Fe in urine.

100

What tests could you do during the acute phase if you suspect paroxysmal nocturnal hemoglobinuria? What could you check for days after the event?

Check blood for hemoglobinemia, urine for hemoglobinuria. Days after the event, iron-laiden renal tubular cells are sloughed off and you could check for hemosiderinuria. 

101

What test is used to screen for PNH?

Introducing sucrose into the serum activates complement, and helps screen for PNH by triggering hemoglobinemia and hemoglobinuria and later on hemosiderinuria.

102

What are confirmatory tests that someone has PNH?

Acidified serum test (activates complement) or lack of CD55 on surface of RBC (requires DAF to bind to RBC) on flow cytometry.

103

A 24 year old man presents with fatigue, shortness of breath and chest palpitations. He also says that his urine is dark colored when he wakes up in the morning. He has a history of multiple DVTs. Labs reveal microcytic anemia, decreased serum iron, decreased serum ferritin, increased TIBC, % saturation is decreased and RDW is increased. What is the major cause of death in patients with this condition?

The main cause of death in people with PNH is thrombosis of hepatic, portal or cerebral veins due to destroyed platelets release of thrombotic factors after destruction by complement.

104

What are the non-lethal complications of PNH?

Iron deficiency anemia from loss of Fe in urine. 10% of patient develop AML because it is also a mutation in the myeloid stem cells.

105

How do RBCs protect themselves from the oxidative stress that surrounds them (oxygen, inflammation, etc.)?

Glutathione. GSH + H2O2 -> GS-SG + H2O. NADPH reduces GS-SG back to GSH so it can continue to reduce oxidative species. G6PD is responsible for production of the NADPH that reduces glutathione.

106

A 37 year old man presents with dark urine and back pain after having a severe bout of the pneumonia. He was given sulfa drugs to treat the infection and symptoms began shortly thereafter. Labs reveal a normocytic anemia and elevated unconjugated bilirubin. Peripheral blood smear is shown below. What is likely causing this man’s symptoms? 

This patient has G6PD deficiency. This is an X-linked recessive disorder causing a reduced half-life of G6PD. Hours after oxidative stress hitting the RBC, Hbg precipitates as a Heinz body, which is removed by splenic macrophages, causing formation of bite cells. This leads some extravascular hemolysis, but predominant intravascular hemolysis. Intravascular hemolysis presents with hemoglobinuria and back pain because Hgb is nephrotoxic.

107

3 patients present to your office. 

The normal half-life of G6PD lasts the entire life of the RBC. The African variant has a mildly reduced half-life (gone in older RBCs) of G6PD. The mediterranean variant has a markedly reduced half-life (gone in younger RBCs) of G6PD.

108

A 37 year old man presents with dark urine and back pain after having a severe bout of the pneumonia. He was given sulfa drugs to treat the infection and symptoms began shortly thereafter. Labs reveal a normocytic anemia and elevated unconjugated bilirubin. Peripheral blood smear is shown below. What are other factors that could cause him to present this way?

Causes of oxidative stress include infections, drugs (primaquine, sulfa and dapsone) and fava beans. All of these can result in hemolytic crisis from G6PD deficiency.

109

How do you screen for G6PD deficiency?

Heinz preparation, highlights the precipitated Hgb within the RBC. G6PD deficiency is confirmed by enzymatic studies once the episode resolves (because all the RBCs w/o G6PD are dead during the acute episode.

110

A 50 year old woman present with extreme pallor, tachycardia, shortness of breath and angina. Labs reveal and elevated reticulocyte count and spherocytes on peripheral blood smear. Her direct Coombs test is positive. History reveals SLE. What is causing her condition?

This patient has IgG-mediated immune hemolytic anemia. IgG binds RBCs in the warm central body. Membrane of antibody-coated RBC is consumed by the splenic macrophages and causes formation of spherocytes. Note that this is associated with SLE, chronic lymphocytic leukemia (CLL) and drugs.

111

A 50 year old woman present with extreme pallor, tachycardia, shortness of breath and angina. Labs reveal and elevated reticulocyte count and spherocytes on peripheral blood smear. Her direct Coombs test is positive. History reveals recent bacterial infection and use of penicillin. Why might penicillin have been the culprit for her condition and what other drug could cause this?

Penicillin binds to the RBC membrane. Then IgG binds to penicillin and causes IgG-mediated immune hemolytic anemia. Methyldopa drives overproduction of autoantibodies and IgG binds antigens that were already present on the RBC and causes immune hemolytic anemia.

112

A 50 year old woman present with extreme pallor, tachycardia, shortness of breath and angina. Labs reveal and elevated reticulocyte count and spherocytes on peripheral blood smear. Her direct Coombs test is positive. History reveals recent bacterial infection and use of penicillin and SLE. How do you treat this patient?

You treat IgG immune hemolytic anemia by 1) removing the drug if it is causing it 2) Giving steroids to inhibit the immune response and antibody deposition on RBCs 3) IVIG to give the splenic macrophages something to eat other than Ig-covered RBCs 4) Splenectomy to remove the source of antibodies.

113

A 50 year old woman present with extreme pallor in the legs and fingers, tachycardia, shortness of breath and angina. Labs reveal and elevated reticulocyte count and RBC aggregates on peripheral blood smear. Her direct Coombs test is negative. History reveals onset of symptoms after snowshoeing in the mountains. What is causing her condition?

This patient has IgM-mediated immune hemolytic anemia. IgM binds to RBCs and induce activation of complement and may result in intravascular hemolysis, despite most hemolysis taking place extravascularly in the liver Kupffer cells. Note that since it is IgM (cold agglutinin) activating complement, most hemolysis takes place in to cooler regions of the body.

114

What infections can cause IgM-mediated intravascular hemolysis?

Mycoplasma pneumoniae and infectious mononucleosis.

115

How do you diagnose immune hemolytic anemias?

Direct Coombs test (Anti-IgG is added to serum and causes agglutination if IgG is bound to RBCs). Indirect Coombs test (Anti-IgG mixed with serum, agglutination occurs if serum antibodies are present)

116

A patient presents with shortness of breath, angina and tachycardia. Labs reveal schistocytes. What condition are these schistocytes a hallmark of?

The patient has microangiopathic hemolytic anemia. This happens as a result of intravascular pathology (usually a microthrombus) that shears RBCs as they pass through circulation, making schistocytes. 

117

What are conditions that can cause microangiopathic hemolytic anemia?

Thrombotic thrombocytopenic purpura (TTP, platelet thrombi form due to lack of enzyme AdamsTS13), HUS from E. Coli O157:H7 toxin (platelet thrombi form), DIC (platelet + fibrin thrombi), Hemolysis Elevated Liver enzymes and low Platelets (HELLP develops in pregnant women that causes thrombus formation in liver vessels), prosthetic heart valves (crush RBCs as they pass) and aortic stenosis (calcified valve crushes RBCs as they pass).

118

A 22 year old service member presents with fatigue, daily fevers, shortness of breath and dark colored urine. She spent a year working in Africa recently. Physical exam reveals splenomegaly. Peripheral blood smear is shown below. What is causing the symptoms in this patient?

Note the small malarial organisms within the RBCs. This patient has malaria from a mosquito bite (anopheles) that transmits plasmodium and it infects RBCs and the liver. This causes intravascular hemolysis from the plasmodium life cycle that causes cyclical fever. Note that there will be some extravascular hemolysis from splenic macrophages eating infected cells and this will cause splenomegaly.

119

What type of malaria produces a daily fever?

P. falciparum. It replicates daily, lyses RBCs daily and thus causes fever daily.

120

What type of malaria produces an every other day fever?

P. vivax and P. ovale. They replicate every other day, lyse RBCs every other day and cause fever every other day.

121

What are the general etiologies of bone marrow insufficiency?

Microcytic & macrocytic anemias, renal failure (decreased EPO) and damage to marrow precursor cells.

122

What happens as a result to damage to the hematopoietic stem cell?

Aplastic anemia, this causes a pancytopenia (low RBCs, WBCs and platelets) and a low reticulocyte count.

123

List 3 etiologies for aplastic anemia

Drugs/chemicals, viral infections and autoimmune damage.

124

Classic biopsy finding of aplastic anemia

Empty, fatty bone marrow

125

How do you treat aplastic anemia?

Stop drugs, transfusions, administer EPO, GM-CSF or G-CSF, immunosuppression with autoimmune etiologies and bone marrow transplant.

126

What is it called when a pathologic process (like cancer) replaces bone marrow and causes anemia?

Myelophthisic process. Hematopoiesis is impaired and causes pancytopenia.