spherocytosis, hereditary

spherocytosis, hereditary A genetic disorder of the red blood cell membrane that is characterized by anemia, jaundice, and enlargement of the spleen (splenomegaly). Abbreviated HS. In HS, the red cells are smaller, rounder, and more fragile than normal. They have a spherical shape rather than the biconcave-disk shape of normal red cells. These fragile red cells (spherocytes) tend to get trapped in narrow blood passages, particularly in the spleen. If this occurs, they break up (hemolyze) where they have lodged, leading to hemolytic anemia. The clogging of the spleen with red cells almost invariably causes splenomegaly. The breakup of the red cells releases hemoglobin, and the heme part gives rise to bilirubin, the pigment of jaundice. Often patients with HS also have iron overload due to the excess destruction of iron-rich red cells. HS often appears in infancy or early childhood, causing anemia and jaundice. Four different abnormalities in red cell membrane proteins have been identified in patients with HS, including deficiencies in the blood cell membrane proteins known as spectrin and ankyrin. Depending upon the specific form, HS may be inherited as an autosomal dominant or recessive trait. Diagnosis is made via laboratory study of the blood. HS is most common in people of northern European descent. Treatment involves removing the spleen (splenectomy). Although the red cell defect persists after splenectomy, the hemolysis ceases and the prognosis after splenectomy is for a normal life expectancy. Also known as congenital hemolytic jaundice, severe atypical spherocytosis, spherocytosis type II, ankyrin deficiency, erythrocyte ankyrin deficiency, ankyrin-R deficiency, and ankyrin1 deficiency.