Microscopic polyangiitis with renal mass-like lesion : A case report

Abstract

A 63-year-old man was admitted to our hospital because of persistent fever, weight loss, painful foot, and purpura on his extremities. He had lower extremity peripheral neuropathy, and skin biopsy of the purpura revealed vasculitis. Serum tests for myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA), proteinase 3-ANCA, and ANCA (indirect fluorescent antibody method) were all negative. Computed tomography revealed a 6-cm large, irregularly shaped lesion in the right kidney, while the nasal sinuses and lungs were intact. Based on these findings, a diagnosis of suspected systemic vasculitis associated with renal cell carcinoma was made. Thus, right nephrectomy was performed. However, the pathological findings showed a large infarct with necrotizing vasculitis of the arcuate, interlobular, and perinephric small arteries and a crescent formation in the glomerulus. Based on these findings, he was diagnosed with microscopic polyangiitis. Due to rapidly worsening symptoms of purpura and neuropathy, treatment with a high dose of corticosteroid was initiated on postoperative day 2, which led to improvement of his symptoms. Vasculitis accompanied with a mass-like lesion is occasionally confused with malignancy. The lesion in our patient was considered to have originated by asymptomatic renal infarction. This case suggests that a renal mass-like lesion with vasculitis should be diagnosed with care.