Not a feature of hereditary Spherocytosis:March 2007
Ans. B: Increased RBC surface areaIt's the only condition presenting with Increased MCHCSpherocytosis is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton, including, spectrin, ankyrin so blood cell contracts to its most surface-tension efficient and least flexible configuration, a sphere( spherocytes).They have a high osmotic fragility and are more prone to physical degradation.They are most commonly found in immunologically-mediated hemolytic anemias and in hereditary spherocytosis, but the former would have a positive direct Coombs test and the latter would not.The misshapen but otherwise healthy red blood cells are mistaken by the spleen for old or damaged red blood cells and it thus constantly breaks them down, causing a cycle whereby the body destroys its own blood supply (auto-hemolysis). Chronic symptoms include anemia and splenomegaly. As a result of the broken-down blood cells -- bilirubin -- accumulates in the gallbladder and can cause pigmented gallstones to develop.In peripheral blood smears, red blood cells will appear abnormally small.The CBC will show elevated MCHC.The bone marrow in its role of manufacturing red blood cells will display hyperplasia, the increased activity of replacing RBCs. As a result, immature red blood cell or reticulocyte counts will appear elevated.
Autosomal dominant
Increased RBC surface area
Increased MCHC
Normal or decreased MCV