Spherocytosis – Top USMLE Diseases

Hereditary spherocytosis (HS) is the most common type of hereditary hemolytic anemia. The condition is caused by a cytoskeletal protein deficiency in the RBC membrane. This results in loss of membrane stability and deformability of the RBC, giving the cell its spherical shape (spherocyte). These cells are predisposed to splenic degradation, leading to hemolysis. Examination may show jaundice and splenomegaly, while laboratory tests are consistent with hemolytic anemia and increased hemoglobin concentration. Among multiple confirmatory tests for HS, the eosin-5’-maleimide (EMA) binding test is preferred. The only definitive treatment for HS is splenectomy.

Autoimmune hemolytic anemia (AIHA) is a rare type of hemolytic anemia characterized by antibody production against self RBCs, leading to destruction of these cells in the spleen and other reticuloendothelial tissues. The disease is generally categorized as warm or cold, depending on the thermal reactivity of the autoantibodies. The etiology is diverse and includes infections, autoimmune diseases, lymphoproliferative disorders, and drugs. The diagnosis is based on laboratory evidence of hemolysis (elevated LDH, indirect bilirubin, reduced haptoglobin) in association with a positive direct antiglobulin test (DAT) or Coombs test. Management involves supportive care, removal of the inciting agent, use of steroids and immunosuppressive agents, and splenectomy in refractory cases.