[Chronic hemorrhagic cystitis induced by cyclophosphamide in dermatomyositis refractory to corticosteroid treatment]

Dermatomyositis was diagnosed at age 7 years to a fourteen year old female. The disease was unresponsive to high doses of prednisone, so she was treated with oral cyclophosphamide 0.8 mg.kg.day (25 mg.m2) but treatment was withheld after sixteen weeks because of hemorrhagic cystitis and changed to azathioprine for two years, which resulted in complete remission of dermatomyositis. Nevertheless silent microscopic hematuria persisted and chronic cystitis was demonstrated by cystoscopy and vesical biopsy at age 13 years. In this case chronic cystitis developed earlier and at lower doses of cyclophosphamide than in other previously reported cases.