Granulomatosis with Polyangiitis Presenting as Asymmetric Oligoarthritis: A Diagnostic Challenge

Granulomatosis with polyangiitis (GPA) is an anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis classically involving the respiratory tract and kidneys. Although musculoskeletal symptoms are common, they are rarely the initial or dominant presentation, which may lead to diagnostic delays. We present the case of a man in his 40s who initially presented with acute asymmetric oligoarthritis and constitutional symptoms. Initial evaluation for infectious and crystal-related etiologies was unrevealing. During hospitalization, he developed cutaneous vasculitic lesions, including punctate digital lesions and subungual hemorrhages, prompting further investigation. Imaging revealed bilateral pulmonary nodules, and serologic testing demonstrated markedly elevated PR3-ANCA levels. Lung and skin biopsies were compatible with early changes of granulomatosis with polyangiitis. The patient demonstrated rapid clinical response to high-dose glucocorticoid therapy. This case highlights the diagnostic challenges of GPA when presenting with predominant musculoskeletal symptoms. Early consideration of vasculitis, timely serologic testing, and tissue biopsy are essential to avoid delays in diagnosis and prevent disease progression.