A case of mixed connective tissue disease (MCTD) complicated with MPO-ANCA-related necrotizing glomerulonephritis.

Renal diseases of mixed connective tissue disease (MCTD) are not unusual. Although most of them are SLE-like renal impairment with immune complex deposits, systemic sclerosis- (SSc) like renal impairments with intimal thickening of interlobular arteries or arterioles are also encountered. Several cases of SSc complicated with MPO-ANCA-related necrotizing glomerulonephritis (nGN) are reported. Here we report a case which developed MPO-ANCA-related nGN 16 years after the diagnosis of MCTD. She exhibited pauci-immune focal nGN and significantly high titer of MPO-ANCA. She was successfully treated with prednisolone and cyclophosphamide. We believe this is the first case in which MPO-ANCA-related nGN was demonstrated in a patient with MCTD.