EMZYMOPATHIES AND MEMBRANOPATHIES Flashcards
What is the structure of the red cell?
A biconcave discallowing flexibility and efficient navigation in narrow capillaries.
Why is red cell metabolism important?
It generates ATP (via anaerobic glycolysis) to maintain shape volume
What are the key enzymes in red cell metabolism?
Glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase.
What is the role of G6PD in red cells?
It reduces NADP to NADPH which keeps glutathione in its reduced form to prevent oxidative injury.
What is the most common cause of red cell membrane disorders?
Defects in cytoskeletal proteins like spectrin ankyrin
What is the pathophysiology of spherocytosis?
Deficiency or structural defects in spectrin reduce surface-to-volume ratio creating less flexible spherical red cells prone to extravascular hemolysis.
What is the pathophysiology of elliptocytosis?
Mutations in spectrin disrupt the cytoskeletal lattice resulting in elliptical-shaped red cells prone to hemolysis.
What are clinical features of red cell membrane disorders?
Anemia jaundice
How is hereditary spherocytosis diagnosed?
Reduced fluorescence in eosin-5-maleimide staining spectrin deficiency on electrophoresis
What is the treatment for hereditary spherocytosis?
Folic acid supplementation splenectomy for severe cases
What triggers hemolysis in G6PD deficiency?
Oxidative stress from infections drugs (e.g.
What are the clinical syndromes in G6PD deficiency?
Acute hemolytic anemia neonatal jaundice
What are Heinz bodies?
Aggregates of denatured hemoglobin visible with special stains
What are key findings in G6PD deficiency during a hemolytic episode?
Anemia bite cells
How is G6PD deficiency diagnosed?
Enzyme assay although levels may be falsely normal during a hemolytic crisis; repeat testing later is advised.
What is the inheritance pattern of G6PD deficiency?
X-linked recessive.
What is pyruvate kinase (PK) deficiency?
An autosomal recessive enzyme defect causing impaired ATP production and rigid red cells leading to extravascular hemolysis.
What are clinical features of PK deficiency?
Milder anemia than G6PD deficiency splenomegaly
What is the treatment for PK deficiency?
Folic acid supplementation transfusions if needed
What complications are common in red cell enzymopathies?
Iron overload gallstones
What is unconjugated hyperbilirubinemia?
An increase in unconjugated bilirubin due to excessive hemolysis leading to jaundice.
What are gallstones in hemolytic anemia composed of?
Pigmented bilirubin stones due to chronic hemolysis.
What is the conclusion about membrane and enzyme disorders?
These inheritable intracorpuscular defects cause hemolytic anemia with membrane defects causing extravascular hemolysis and enzyme defects causing mixed hemolysis.
