Hematology - Hemolytic anemias
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- What is hemolytic anemia?
- A hemolytic state occurs when the RBC survival is shortened. Anemia when rate of hemolysis faster than bone marrow can compensate.
- Consequences of intracorpuscular membrane defects:
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Decreased membrane stability
decreased cellular flexibility
loss of membrane
loss of biconcave shape - What is Hereditary Spherocytosis?
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genetic disorder of RBCs that make them prone to hemolysis.
RBCs have decreased S:V ratio.
Spherocytes on the blood smear are diagnostic of spherocytosis. - what are the possible defected proteins in Hereditary Speherocytosis?
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spectrin*
ankyrin*
band 3
palladin
*most common defects - Pathophysiology of HS
- cytoskeleton uncouples from lipid bilayer. RBCs become trapped in & conditioned in spleen.
- Characteristics of the spherocytes in HS
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Decreased surface area:volume
increased cytoplasmic viscocity: decreased deformibility
membrane has decrease in total lipids: no proteins to hold lipids in place
abnormally permeable to Na+
easily trapped in spleen - clinical features of HS
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1. jaudice, anemia, splenomegaly
2. all ages affected
3. variable hemolytic state: severity depends on ability to compensate
4. gallstones in older, untreated pts. - Lab findings of HS
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1. mild anemia
2. INCREASED retic count RPI>2
3. sphero, polychrom, anis, poik
4. MCV & MCH usually NORMAL
5. MCHC >36% (HYPERCHROMIC)
6. increased bilirubin, osmotic fragility
7. negative antiglobluin test - Therapy of HS
- splenectomy
- What is Hereditary Elliptocytosis (HE)?
- group of disorders characterized by large #'s of elliptical RBCs in peripheral blood.
- etiology & pathophysiology of HE
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deficiency in band 4.1
decreased assoc. of spectrin dimers to tetramers caused by abnormal spectrin chains
abnormal interactions among several membrane proteins
other molecular abnormalities - interesting clinical features of HE
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90% of patients have no clinical symptoms
10% of patients have chronic hemolytic state - lab findings of HE
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variable depending on subgroup
ELLIPTOCYTOSIS ALWAYS PRESENT - What is hereditary pyropoikilocytosis (HPP)?
- rare hemolytic anemia characterized by thermal sensitivty of RBCs. Variant of HE
- Hallmarks of HPP
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1. bizarre micropoikilocytes in which red cell budding, microspherocytes & elliptocytes are present
2. increased thermal sensitivity of RBC membrane
3. autosomal recessive inheritance - etiology/pathophysiology of HPP
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horizontal, vertical defects combine to cause membrane instability.
-spectrin self-association (horizontal) impaired
-spectrin deficiency (vertical) impaired - Clinical features of HPP
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SEVERE hemolytic anemia
evident in infancy or early childhood - Lab findings of HPP
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low MCV - many fragmented cells
striking morphologic abnormalities on blood smear
(elliptocytes, fragments, spherocytes)
increased osmotic fragility - Therapy for HPP
- splenectomy. if it is severe, transfusions may be necessary