HELLP diagnostic criteria (low serum haptoglobin levels and elevated indirect bilirubin levels in association with elevation in liver enzymes after ruling out other causes of hemolysis and thrombocytopenia) are not useful for discriminating between hereditary TTP and HELLP because both diseases may be associated with thrombocytopenia and hemolytic anemia with microangiopathic changes on the peripheral blood smear [11]. The gene discussed is HP; the disease is thrombotic thrombocytopenic purpura.