Microscopic polyangiitis with dermatomyositis.

Dermatomyositis is a rare autoimmune disease with a heterogeneous presentation that often has multiple extramuscular manifestations, although it does not typically involve the renal function. A 62-year-old female presented with proximal muscle weakness and rashes, which are classic symptoms of dermatomyositis without creatine kinase (CK) elevation. Initial serologic evaluation revealed a positive p-ANCA, although she did not develop renal failure for several months, at which point renal biopsy findings were consistent with microscopic polyangiitis. The patient was initially treated with cyclophosphamide, maintained with rituximab, and has been in remission for more than 2 years. Dermatomyositis and microscopic polyangiitis are both uncommon diseases, but are concomitantly present in this patient. A positive p-ANCA and development of renal insufficiency should be promptly evaluated in dermatomyositis patients.