Test 3: Hemoglobinopathies Flashcards by Sarah King

-disease state involving the hemoglobin molecule
-due to a genetic mutation in one or more genes that affect hemoglobin synthesis
-mutation effects either the quality or quantity of hemoglobin synthesis

Hemoglobinopathy

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Hemoglobinopathy Effects either the quality or quantity of hemoglobin synthesis
____________ = qualitative
____________ = Quantitative

Structural defects
Thalassemias

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There are ____ functional human globin genes located on ____ different chromosomes

6, 2

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________ and _______ are located on chromosome ___, and I referred to as alpha-like genes.

Alpha, zeta

-chromosome 16

(Two alpha and one zeta globin genes per chromosome)

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________, __________, ________ and _________ are located on chromosome 11 and are referred to as beta-like genes.

Beta, gamma, delta, epsilon

(two Gamma and one beta, Delta, and alpha globin per chromosome)

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There are more than 1000 structural hemoglobin variants currently they are divided into what five categories?

-Point mutation (most common, 90%)
-Deletion
-Insertions
-chain extensions (Stop codon is mutated, produces abnormally long globin chains affecting structure and function)
-Gene fusions- Produces abnormal folding of chains and effects hemoglobin function

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What are the lab tests done for hemoglobinopathys?

• traditional hematology (CBC and microscopic)
• Hemoglobin electrophoresis testing
• HPLC (High performance liquid Chromatography)
•PCR

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What is the easiest and cheapest test done for hemoglobinopathies?

Hemoglobin electrophoresis
-Cellulose acetate (pH 8.4)
-Citrate agar gel (pH 6.2)

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Both beta genes are mutated resulting in absence of hemoglobin A. What are the two types?

Homozygous Beta-Hemoglobinopathies

-Sickle cell (Hb SS)
-Hgb C disease (CC)

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When only one gene is mutated and the other is normal.
Attempt to minimize the impact of abnormal hemoglobin, presents variant hemoglobin in lesser amount then hemoglobin A

Heterozygous beta-Hemoglobinopathies

Hgb S trait (HB AS) and Hgb C disease (Hb AC)

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The most frequently occurring and the most severe of the abnormal hemoglobins
Symptomatic Hemoglobinopathy in which patients Expresses either hemoglobin SS or S in combination with another hemoglobin beta chain mutation

Sickle cell disease (SCD)

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SCD is caused by point mutation at the _______ amino acid in beta chain.
What type of mutation is it?

6th *
Point mutation*

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In SCD, what amino acid is substituted in the 6th amino acid position?

VALINE substitutes for glutamic acid**

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Presence of just one sickle cell gene confers resistance to cerebral infection by…

Plasmodium falciparum

-When a malaria infected RBC sickles, the parasite dies

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How common is sickle cell disease in the African-American population?

8 to 9% carry the trade. One in 300-600 are affected by SCD

-severe, moderate, and mild forms all exist. Unknown etiology as to variance in severity

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Pathophysiology of SCD

When hemoglobin switches from relax to tense forms as it offloads O2 in capillaries, Hemoglobin a structural changes shape in such a way to bring it hydrophobic, sticky, mutated Valine into contact with each other, resulting in…
-Polymerization of the hemoglobin
-”locking up” of spectrins flexibility
-Bizarre deformation of the RBC
(Usually reversible, but depends on time, temperature, PH, and oxygen tension)

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SCD damages _____ channels of cell.

Potassium

RBC loses potassium and dehydration results leading to formation of intracellular crystals and further deformation. Hemoglobin molecule stack up “like firewood”
-RBCs are much more fragile and lyse easier

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Sickle cell leads to __________ Blood viscosity and _________ Blood flow.

Increased, slow

(This can prolong exposure to hypoxic environment, and lower tissue pH decreasing the oxygen affinity that further promotes sickling)

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What is responsible for vaso-occlusion complications in SCD?

Irreversible sickle cells are removed by the spleen, but reversible cells are responsible for the vaso-occlusion complications

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Chronic injury response Means “ Sickle cell ________” Patients have increased numbers circulating endothelial cells which trigger the extrinsic coagulation pathway and promote formation of microthrombi, which cause Further necrosis that promotes a vicious cycle.

Crisis

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What is the reason SCD patients usually get hospitalized?

Vaso-occlusion

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Polychromasia and __________ Are typically found with sickle cell.

Codecytes

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What ends up happening to hemoglobin S RBCs?

Permanently destroyed by the spleen (Extravascular hemolysis)

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In SCD, Bone marrow responds with increased erythropoiesis. And severe anemia marrow space is widen, bone cortex thins out, and extra medullary sites for hematopoiesis are recruited. Where are these sites?

liver, spleen, and thymus

Overtime the spleen quits effectiveness

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SDC causes a chronic, low level, intravascular hemolytic anemia. RBCs only have a lifespan of ______ days.

10-20 Enlarged spleen and sometimes spleen is removed

Seen in patients with SCD that is caused by any situation that produces excessive deoxygenation of RBCs Like hyper or hypo thermia, dehydration, infection, intense exercise, labor and delivery, and high altitude transitions

Sickle cell crisis -About 80% of patients only have a rare crisis

what are the five types of sickle cell crises?

• Vaso-occlusion or pain crisis • infectious crisis • Bone and joint crisis • Splenic sequestration crisis • aplastic crisis

Type of SCD crisis that is characterized by rigid, sickle cells that increase blood viscosity and cause vascular occlusion and micro thrombi (strokes), Resulting in tissue necrosis. Number one cause of death in adult sickle cell patients

Vaso-occlusion or a chest crisis (Called a cute chess syndrome, ACS, when it predominantly effects lungs)

What is the number one cause of death in sickle cell adult patients?

Vado-occlusion or pain crisis (or acute chest syndrome when in lungs)

Type of sickle cell crisis that is precipitated by infection and is the primary cause of death in SCD children

Infectious crisis (S. aureus, S. pneumonia, and H. flu)

What is the number one cause for death and hospitalization in SCD patients?

Vaso-occlusion

Type of a sickle cell crisis where pain occurs in bones and joints (“Sympathy response”) as sickle cells accumulate in bone shafts. Bone marrow actually infarcts.

Bone and joint crisis

Type of sickle cell crisis that occurs when enough sickle cells are trapped in the hypoxic, convoluted, splenic microcirculation. Becomes a vicious cycle as a spleen in larges and then traps even more cells. Hypovolumetric shock can happen due to extreme drop in blood volume.

Splenic sequestration crisis

How is splenic sequestration crisis monitored?

By a “pit count”, The number of pits in RBC membrane Increased number of pits = worsening splenic function

What is usually the first clinical finding in infants with severe SCD?

Dactylitis -Due to painful extramedullary hematopoiesis

Type of sickle cell crisis where there is a decreased bone marrow hematopoiesis thought to be triggered by infection/fever.

Aplastic crisis (Common with parvovirus B19) * Result in temporary decrease in RBC count, Hgb, Hct, and RPI

Lab findings for SCD

-normo-, normo- anemia -modified to marked Aniso (sickled cells, target cells) Polychromasia due to reticulocytosis, and basophilic stippling -Increased RDW -Howell-jolly and Pappenheimer bodies

Why are Howell-jolly and Pappenheimer bodies present in SCD patients?

If spleen worked, most would have been removed already

What is the most common screening test for SCD that is not diagnostic?

Hemoglobin solubility test*

How is hemoglobin solubility test done?

-blood is added to a reducing agent *Sodium dithionate* and a lysing agent that releases the Hemoglobin from the RBCs -deoxygenated hemoglobin S is insoluble and precipitates in solution to give a turbid result

What can get a false positive result and what can give a false negative result on the hemoglobin solubility test?

-False positive with hyperlipidemia -false negative results with low hematocrit or low RBC counts

All hemoglobins with the amino acid substitution found in hemoglobin _____ Will give a positive hemoglobin solubility test result even if there is a second substitution.

Lab test that shows 80 to 90% hemoglobin S Remainder is usually F and A2

Alkaline electrophoresis

Test that I can qualify low amounts of A2 and F

HPLC (High performance liquid chromatography)

A definitive test for SCD that can use peripheral blood, CVS, amniotic fluid, or even IVF samples

DNA sequencing

What allows for hemoglobin electrophoresis testing?

Hemoglobin carries an electrical charge depending upon the amino acid sequence of globin chains and the pH of the surrounding environment

What are treatment strategies for CDC?

1. Prevent crisis by avoiding precipitating situations 2. Hydroxyurea- For ages three and up. Antineofplastic drug induces increased hemoglobin F production (decreases WBC count and inhibits overall inflammatory response) Side effect of macrocytosis 3. Bone marrow transplant (Only known cure) 4. Gene therapy possible in 10 to 20 years 5. New anti-sticking agents (NAC) 6. Prohylaxtic penicillin for children 7. Pneumococcal vaccine 8. Stem cell transplants from cord blood

What is the average life expectancy for patients with SCD?

45 to 50 years

What symptoms do patients with sickle cell trait (AS) Typically have?

These patients usually have no symptoms because majority of their hemoglobin is A -Rare occasions can have crisis in states of extreme tissue hypoxia

What is the RBC morphology for patients with sickle cell trait?

Mostly normal except for a few targets and VERY RARE sickled cells

What result is typically seen for solubility test for patients with sickle cell trait?

Positive

_______% hemoglobin S on hemoglobin electrophoresis for patients with sickle cell trait

30-45

What is the treatment and prognosis for patients with sickle cell trait?

-usually no treatment -Typically have normal lifespan and quality of life and also have increased resistance to malaria

Hemoglobin C disease (CC) is caused by an amino acid point substitution by what amino acid at the _____th position?

Lysine instead of glutamic acid (Lysine = C) 6th

What population is hemoglobin C disease common in?

Black populations and it is the second most common hemoglobin variant worldwide

Hemoglobin as polymers are long and thin, and he will go and see polymers form a ________________ within the RBC

Short, thick crystal

Hemoglobin C crystals do ____ change the shape of the red cell. Vaso-inclusion does ______ occur.

not not

What are the symptoms and treatment for hemoglobin C disease?

-Usually the crystals are removed by spleen, but if spleen is nonfunctional, crystals will appear in peripheral blood RBCs -Lots of extravascular homolysis happening -Patients may Have splenomegaly And abdominal pain, but usually no other symptoms and no treatment required

What are the typical lab findings in hemoglobin C disease?

-mild to moderate normo-, normo-anemia -some microcytosis and mild hypochromasia -variable target cells, spherocytes -Increased retic count by 4 to 8% -hemoglobin C crystals in peripheral blood ( shaped like thick or elongated hexagons) **** Negative hemoglobin solubility test

True or false, Pt with hemoglobin C disease will have a positive hemoglobin solubility test.

False

What causes decreased RBC survival in hemoglobin CC patients?

Removal of hemoglobin C crystals by spleen

What are the typical findings for hemoglobin C trait (AC)?

-no symptoms or anemia -40% target cells, slight hypochromasia -Percentage of hemoglobin A is greater than hemoglobin C

How is a definitive diagnosis of hemoglobin C made?

With electrophoresis

With hemoglobin CC, cellulose acetate electrophoresis shows _____ Hgb A and shows Hgb C….

No, Comigrating with A2, E, and O

With hemoglobin a C, electrophoresis shows about _____% Hgb A and ____% Hgb C.

60, 30

How will hemoglobin C migrate on citrate agar at an acid pH?

As a separate band

On Cellulose acetate, what all co-migrates with C?

CEOA2

-*This disease involves two different amino acid substitution on each of the two beta globin chains -The most common double heterozygous syndrome resulting in a structural defect of the hemoglobin molecule -generally milder symptoms than sickle cell disease, less frequent and less disabling vaso-occlusion complications

Hemoglobin SC disease

What is the morphology of hemoglobin SC disease?

-Normo-, normo- anemia -Typically see many target cells and folded or “pocketbook” cells

When crystals are seen in SC disease how do they typically appear?

Fingerlike projections, producing “Washington Monument” or “mitten cells”

Does hemoglobin SC disease Cause a positive or negative solubility test results?

Positive

Hemoglobin SC disease: On cellulose acetate electrophoresis, hemoglobin C and Hemoglobin S are seen in what ratio?

Equal amounts

What is the prognosis for patients with hemoglobin SC disease?

Relatively normal life span of 60 to 70 years. Can have diminished quality of life due to retinal lesions

The third most common hemoglobin variant in the world, particularly in south east Asian population (13%)

Hemoglobin E Seen in Laos, Cambodia, Thailand

Hemoglobin E involves a substitution of ___________ Instead of glutamic acid in the ______th Position.

Lysine, 26

Homozygous state of hemoglobin E variant makes up more than _____% Hemoglobin E

What is the morphology seen in hemoglobin E Patient?

Micro-, normo- anemia with MANY target cells

Hemoglobin E can occur in combination with…..

Beta-thalassemia

What is hemoglobin AE called?

Hemoglobin Etrott

Group of variants that migrate in Alkaline pH at the same electrophorphoretic position of hemoglobin S (due to their charge)

Hemoglobin D and hemoglobin G

Hemoglobin D and hemoglobin G cause _____ Hemolytic anemia.

Mild (like cc and a C)

What result does hemoglobin D and hemoglobin G give on solubility test?

Negative

Patients with hemoglobin D and hemoglobin G are clinically normal but may have some ___________.

Splenomegaly

Cellulose acetate electrophoresis shows 95% hemoglobin D, which migrate to same position as S on cellulose acetate, but co-migrates with hemoglobin A1 and A2 on citrate agar. This should make you suspicious where did the apparent hemoglobin S go? This requires what test for confirmation?

High pressure liquid chromatography

-particularly common in Arabic populations -mild hemolytic anemia with many target cells

Hemoglobin O or (O-Arab)

How is hemoglobin O differentiated from hemoglobin C?

By electrophoresis

In hemoglobin O glutamic acid is replaced by lysine in the _____ amino acid of beta chain (Same as hemoglobin C, but with different substitution point)

121st

-Involves amino acid substitution that disrupt physical contact between heme and globin -results in hemoglobin denaturation, then precipitation of globin chains, leading to formation of Hines bodies

Unstable hemoglobins

Unstable hemoglobins pre-disposes RBCs to develop a __________ anemia.

Hemolytic (Extravascular removal)

Heinz bodies =

Denatured hemoglobin

What are the symptoms of unstable hemoglobin?

Range from mild to severe, with episodes of Hema lysis and subsequent jaundice

All patients with unstable hemoglobin are which? Homozygous Heterozygous

Heterozygous (all)

What is the most common example of unstable hemoglobins?

Hgb(koln) Old name was congenital Heinz body hemolytic anemia *Hgb Koln heterozygous

What are the lab findings for unstable hemoglobins?

-decreased MCV, MCH, and MCHC (Due to hemoglobin lost when Heinz bodies are removed by spleen) -Aniso, poik, Polychromasia, basophilic stippling, and “bite cells”

What are the two hemoglobins with altered O2 affinity?

-Hgb(Chesapeake) -Hgb(Kansas)

Hemoglobin with altered O2 affinity: Increases O2 affinity that results in a shift to the left. What type of chain variant is it?

Hgb(Chesapeake) alpha chain variant

Hemoglobin with altered O2 affinity: Decrease 02 affinity that results in a shift to the right

Hgb(Kansas)

What is the pathophysiology of hemoglobins with altered O2 affinity?

-disrupted 2,3-DPG binding sites, OR -Disrupted binding of heme to globin, OR -stabilize iron in oxidized Fe3+ state (ex: Hgb. M) All of these will either increase or decrease delivery of oxygen

Hemoglobin with iron stuck in the Ferric state

Methgb

MetHgb can be caused by:

-inherited MetHgb Reductase deficiency -Toxic exposure in newborns, overwhelms GSH’s reducing ability -inherited cytochrome deficiencies, interferes with NADH regeneration via electron transport chain -Genetic mutation in globin chain sequence (only one called hemoglobin M*)

There are five genetic variants known of hemoglobin M, they can affect ____ or ____ chain. Most common in what population?

Alpha, beta Japanese population

What is the pathophysiology of hemoglobin M?

Amino acid substitution prevents Fe3+ Reduction, so Fe remains in ferric state.

Hemoglobin M this type of auto-oxidation, which denatures globin chains, that triggers hemoglobin precipitation and forms ____________.

Heinz bodies

Only heterozygotes (With about ______% Hgb M) exist; Homozygous condition is not consistent with life.

20-30

Hemoglobin M has a characteristic _________ color blood Due to chronic cyanosis

Brownish

There is no treatment available for hemoglobin M. What condition develops to compensate for chronically decreased oxygen delivery?

Compensatory erythrocytosis

Test that is an acid-elution cytochemical method Used to quantitate fetomaternal hemorrhage. And identify cells containing hemoglobin F, based upon the fact that they resist acid-elution to a greater extent then do normal cells. It can also be used when the persistence of hemoglobin F is suspected in hereditary persistence of hemoglobin F, sickle cell, acquired aplastic anemia, thalassemia, and other hemoglobinopathies.

Kleihauer Betke Test

What sample is used for Kleihauer Betke Test?

Specially prepared slide containing the maternal blood sample

What is a normal result for the Kleihauer Betke Test?

0-0.1% Fetal cell % = Number of fetal cells counted x 100% / total # of RBCS

Test 3: Hemoglobinopathies Flashcards

(109 cards)