Membrane Disorders Inherited red cell membrane defects include hereditary spherocytosis, hereditary elliptocytosis, hereditary stomatocytosis, and pyropoikilocytosis. In each abnormalities of the red cell membrane result in hemolysis. Spherocytes have reduced surface membrane area relative to the RBC volume.
Spherocytes are osmotically fragile compared to normal RBCs.
Spherocytes, being less flexible than normal RBCs, are destroyed in the spleen, often causing splenomegaly. Hereditary spherocytosis is most common in people of northern European ancestry. Although a spectrin deficiency is seen in nearly all HS patients, it is thought that the principle defect is an abnormality of the membrane protein ankyrin . Portions of the phospholipid bilayer form vesicles and are lost from the RBC surface resulting in decreased surface area and spherocytosis. Usually the osmotic fragility test results are graphed and reported as shown below.