Snap Shot A 17-year-old Norweigan presents with RUQ pain. Ultrasound reveals a calculi present in the gallbladder. Physical exam shows mild splenomegaly. Her labs show a mild normocytic anemia with an elevated reticulocyte count. Peripheral blood smear shows that many of her RBCs have no area of central pallor. Direct antiglobin test is negative. Introduction An autosomal dominant intrinsic hemolytic anemia (defect in RBCs) Caused by a deficiency in spectrin in the RBC membrane leads to fragility cells have a spheroid shape due to the lack of spectrin get lysed in the spleen by macrophages Most common cause of inherited hemolytic anemia in Northern Europeans Always suspect extravascular (may be intrinsic or extrinsic) hemolysis, especially hereditary spherocytosis in young patients with gallstones, anemia, and splenomegaly Presentation Presents with normocytic, hemolytic anemia jaundice childhood gallstones pigmented splenomegaly Ocasionally patients develop severe anemia, termed an "aplastic crisis" almost always caused by a parvovirus Evaluation Diagnosis is facilitated by the presence of a family hisotry Labs elevated indirect bilirubin direct antiglobulin test (Coombs test) is negative elevated reticulocyte count indicates increased turnover of RBCs in response to hemolysis CBC shows decreased MCV and increased MCHC RBC osmotic fragility test spherocytes lyse easier than normal RBCs Peripheral blood smear shows spherocytes (not schistocytes) lack central pallor and are smaller and rounder than normal red cells Differential Must be distinguished from autoimmune hemolysis, which also has spherocytes autoimmune hemolysis is Coombs positive note it is also osmotically fragile Treatment Folic acid Splenectomy for severe disease Prophylactic immunization against S. pneumonia, H. influenzae, and N. meningitidis (encapsulated organisms)