Myeloperoxidase-antineutrophil cytoplasmic antibody-related crescentic glomerulonephritis after treatment for clinically amyopathic dermatomyositis: a coincidental combination or not?

A 60-year-old Japanese man exhibited rapidly progressive glomerulonephritis 10 years after receiving prednisolone therapy for clinically amyopathic dermatomyositis (CADM). Upon admission, there were no signs of dermatomyositis. Laboratory analyses revealed the presence of myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) at 1,280 EU in the absence of anti-glomerular basement membrane antibody and anti-melanoma differentiation-associated gene 5 antibodies, which are typically expressed in CADM. A renal biopsy demonstrated that 14 of 29 glomeruli showed global sclerosis, and the remaining 15 glomeruli exhibited fibrotic and fibrocellular crescent formation without immunoglobulin and complement. Following treatment with 500 mg/day methylprednisolone pulse therapy for 3 days, the patient was started on 30 mg/day of prednisolone orally. On the third day of hospitalization, we began hemodialysis for uremia and anuria with three treatments of plasma exchange starting on the tenth hospital day. Unfortunately, the patient's renal function did not recover, despite decreases in CRP and MPO-ANCA levels to the normal range. This case is the first English language report of MPO-ANCA-related crescentic glomerulonephritis in a patient who had recovered from CADM.