Sir.—Cyclophosphamide is an alkylating agent frequently used to prepare patients for bone marrow transplant (BMT). Hemorrhagic cystitis may accompany its use; prophylactic forced diuresis has met with limited success in preventing this complication.1 Cyclophosphamide also impairs water excretion, so that administration of extra fluid puts the patient at risk for water intoxication.2 We report the occurrence of water intoxication during cyclophosphamide therapy for BMT in a boy with Wiskott-Aldrich syndrome (WAS). Treatment with 2-mercaptoethane sulfonate (MESNA), a specific inhibitor of cyclophosphamide's urotoxic metabolite acrolein, 3 protected the patient from hemorrhagic cystitis despite fluid restriction and continued use of cyclophosphamide.
Patient Report.—An 8-year-old boy was admitted with a history of eczema, thrombocytopenia, and recurrent infection. The skin was notable for petechiae and healing bruises. The platelet count was 19 000/mm3 (19× 109/L). The boy was histocompatible at the HLA-A, -B, -C, and -DR loci