Which of the following is not seen in Hereditary Spherocytosis
Ans. is 'a' i.e., Direct Coomb's positive Hereditary Spherocytosis Membrane cytoskeleton that lies closely opposed to the internal surface of the plasma membrane, is responsible for elasticity and maintenance of RBC shape. Membrane skeleton consists :? Spectrin - The chief protein component responsible for biconcave shape. Ankyrin and band 4-2 - Binds spectrin to band 3 Band 3 - A transmembrane ion transpo protein. Band 4.1 - Binds spectrin to glycophorin A, atransmembrane protein. Hereditary spherocytosis is an autosomal dominant disorder characterized by intrinsic defects in red cell membrane. This results in production of red cells that are sphere (spherocytes) rather than biconcave. The mutation most commonly involves the gene coding for ankyrin, followed by Band-3 (anionic transpo channel), spectrin, and Band 4.2 (also called palladin). Also know Most common, defect in hereditary elliptocytosis is in spectrin Pathogensis of Hereditary spherocytosis Loss of membrane cytoskeleton proteins (ankyrin, spectrin, Band 3, 4.2) results in reduced membrane stability. Reduced membrane stability leads to spontaneous loss of membrane fragments during exposure to shear stresses in the circulation. The loss of membrane relative to cytoplasm forces the cells to assume the smallest possible diameter for a given volume cells become microspherocytes. Because of their spheroidal shape and reduced membrane plasticity, red cells become less deformable and are trapped in to spleen as they are unable to pass through the interendothelial fenestrations of the venous sinusoids. In the splenic sinusoides, red cells are phagocytosed by RE cells Extravascular hemolysis. Clinical features of Hereditory spherocytosis The clinical features are those of extravascular hemolysis : Anemia - Mild to moderate Jaundice (Mainly indirect bilirubin) - Splenomegaly Gall stones - Elevated excretion of bilirubin promotes formation of pigment stone. Leg ulcer - Rare clinical manifestation. Aplastic crisis - Triggered by parvo-virus infection. Laboratory findings Spherocytosis --> Peripheral smear shows microspherocytes which are small RBCs without central pallor (Normally central 1/3 pallor is present in red cells). MCV4 MCHC r Increased unconjugate bilirubin Urine urobilinogen 1' Stool stercobilinogen Reticulocytosis -4 As seen with any type of hemolytic anemia. Hemoglobin 1 Serum Heptoglobin --> Nonnal to decreased. Increased osmotic fragility on pink test. Coomb's test is used to distinguish hereditary spherocytosis from autoimmune hemolytic anemias. Autoimmune hemolytic anemias are coomb's positive_ whereas hereditary spherocytosis is coomb's negative.
Direct Coomb's Positive
Increased Osmotic Fragility
Splenomegaly
Gall stones