Acute leukemia: an association with atypical hemolytic uremic syndrome

A 5-year-old boy was admitted for anemia, thrombocytopenia, and azotemia. Bone marrow examination demonstrated only erythroid hyperplasia, and he was diagnosed with an atypical form of hemolytic uremic syndrome (HUS). He was treated with daily prednisolone, and hematological profiles and renal function normalized 1 month later. However, heavy proteinuria persisted, and renal biopsy findings were consistent with HUS. Four months later, pancytopenia developed with recurrence of azotemia, and a second bone marrow examination revealed acute lymphoblastic leukemia (ALL). The remission of proteinuria with no recurrences of HUS after antileukemic treatment suggests that the HUS was associated with the ALL.