Microscopic Polyangiitis Histopathologically Confirmed By Lung Biopsy and Rheumatoid Arthritis: A Case Report

Microscopic polyangiitis (MPA) is a systemic necrotizing vasculitis affecting small vessels. MPA is associated with renal dysfunction in most cases and occasionally with pulmonary hemorrhage. However, inflammatory polyarthritis is a rare manifestation. Here, we report the case of a 26-year-old man with MPA who developed rheumatoid arthritis. The patient presented with fever, general fatigue, weight loss, hemoptysis, polyarthritis, and macular rash. Clinical examination showed pulmonary capillaritis. Pathological findings revealed vasculitis of small vessels, including cutaneous leukocytoclastic vasculitis by the skin biopsy. MPA was diagnosed based on clinical symptoms, elevated perinuclear antineutrophil cytoplasmic (p-ANCA) antibody testing and the histopathological findings of lung biopsy specimens. The patient also had rheumatoid arthritis with positive anti-CCP antibody. He had no renal involvement and a negative antiglomerular basal membrane. We aimed to draw attention to the differential diagnosis of joint involvement with a case presenting MPA and RA coincidence.