A Rare Presentation of Granulomatosis With Polyangiitis: A Case Report and Literature Review.

Granulomatosis with polyangiitis (GPA) is a rare ANCA-associated necrotizing vasculitis that predominantly affects the respiratory tract and kidneys. Gastrointestinal involvement is uncommon, and pancreatic manifestations are exceedingly rare. Diffuse alveolar hemorrhage (DAH) represents a severe and potentially fatal complication. We report a 44-year-old male who was initially diagnosed with a pancreatic mass suspicious for malignancy and planned for pancreatectomy. During hospitalization, he developed acute respiratory distress with hemoptysis. Imaging revealed diffuse ground-glass opacities consistent with DAH and a bulky pancreatic tail lesion. Laboratory investigations demonstrated severe anemia, urinary abnormalities suggestive of glomerulonephritis, and strongly positive c-ANCA. A diagnosis of granulomatosis with polyangiitis was established based on clinical, radiological, and serological findings. The patient was treated with intravenous methylprednisolone pulse therapy followed by rituximab induction, leading to rapid clinical improvement and stabilization. He remained asymptomatic during follow-up. This case highlights an extremely rare presentation of GPA with pancreatic mass and diffuse alveolar hemorrhage, emphasizing the importance of considering vasculitis in atypical pancreatic lesions with systemic manifestations to enable early diagnosis and appropriate immunosuppressive therapy.