mlab 1415-hematology keri brophy-martinez chapter 16: hemolytic anemias: enzyme deficiencies
TRANSCRIPT
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MLAB 1415-Hematology
Keri Brophy-Martinez
Chapter 16: Hemolytic Anemias: Enzyme Deficiencies
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Introduction
Enzyme deficiency within the rbc leads to hemolytic anemia
Deficiencies compromise the integrity of the cell membrane or hgb causing hemolysis
Most common are those associated with hexose monophosphate shunt and glycolytic pathway
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Review of RBC Metabolism
Enzymes within the rbc are limited Enzymes that protect the cell from oxidant
damage and provide the cell with energy are essential for cell survival
Mature rbcs depend entirely on anaerobic glucose metabolism for energy needs
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Clinical Findings
Normocytic, normochromic anemia Reticulocytosis Hyperbilirubinemia Neonatal jaundice
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HEREDITARY ENZYME DEFICIENCIES
Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD)
Sex-linked(X) disorder Affects Africans, Chinese, and Mediterraneans Most common enzyme disorder Denatured hemoglobin precipitates in the RBC after
exposure to oxidative stress causing hemolysis
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HMP Shunt: Normal Function
GSH levels maintained by NADPH to NADP
NADP is reduced back to NADPH by G6PD
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HMP Shunt: Deficient
Oxidizing agent causes increase of NADPH
System is overwhelmed
Oxidized hgb accumulates as Heinz bodies
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Causes of oxidative stress
Ingestion of oxidative drugs Antimalaria drugs (i.e Primaquine) Quinine, quinidine Analgesics
Ingestion of fava beans Favism is found in the Mediterranean area
Person eats or inhales fava bean or its pollen Hereditary
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Laboratory features: G6PD deficiency
Decreased H&H (hemoglobin and hematocrit)
HemoglobinuriaIncreased bilirubin and LDReticulocytosis
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Morphology
Blister cell Bite cell
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HEREDITARY ENZYME DEFICIENCIES
Pyruvate kinase deficiency (PK) Autosomal recessive anemia Red cells are unable to retain water which results
in hemolysis, due to cell shrinkage, distortion of shape and increased membrane rigidity
Pyruvate kinase is an essential enzyme in the Glycolytic/Embden-Meyerhof pathway
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Glycolytic Pathway: Normal
PK converts PEP to pyruvate, with the conversion of ADP to ATP
PEP
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Glycolytic Pathway: Deficient
Energy can not be produced, due to lack of ATP
Results in alteration of rbc membrane, dehydration, pump malfunction
PEP
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Clinical Findings
Symptoms vary depending on the degree of the anemia
Jaundice Gallstones
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Laboratory features of PK
H&H - slight↓ to marked ↓ P.S
severity of anemia dictates degree of reticulocytosis, polychromasia, aniso, poik and NRBC’s.
Definitive test is PK enzyme assay. Fluorescent screening
test
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Referenes
Harmening, D. M. (2009). Clinical Hematology and Fundamentals of hemostasis (5th ed.). Philadelphia, PA: F.A. Davis Company.
McKenzie, S. B. (2010). Clinical Laboratory Hematology (2nd ed.). Upper Saddle River, NJ: Pearson Education, Inc.
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