Spherocytosis is an anemia characterized by red blood cells that are sphere-shaped, rather than donut-shaped. Spherocytes are most commonly found in immunologically-mediated hemolytic anemias and in hereditary spherocytosis. The former would have a positive direct Coombs antibody test; the latter would not.
Hereditary spherocytosis is caused by a molecular defect in one of the proteins of the red blood cell cytoskeleton (usually ankyrin, sometimes spectrin). It is an autosomal dominant trait.
