Microscopic polyangiitis: Atypical presentation with extensive small bowel necrosis, diffuse alveolar hemorrhage, and renal failure

Microscopic polyangiitis is an uncommon systemic vasculitis of varying severity that is associated with myeloperoxidase (MPO) and perinuclear antineutrophil cytoplasmic (p-ANCA) antibodies. The most commonly affected organs are the lungs and kidneys. We report on a very unusual case of microscopic polyangiitis presenting with severe mesenteric ischemia in addition to diffuse alveolar hemorrhage and acute renal failure. The patient was initially diagnosed with acute pancreatitis at an outside facility given his severe abdominal pain and elevated pancreatic enzymes. Further investigations after transfer to our facility determined that the patient was actually suffering from a severe exacerbation of previously diagnosed microscopic polyangiitis. He quickly developed diffuse alveolar hemorrhage (DAH) necessitating intubation and acute kidney injury (AKI) requiring dialysis. He subsequently developed mesenteric ischemia and bowel necrosis resulting in emergent laparotomy and extensive small bowel resection. Physicians need to be aware that microscopic polyangiitis can very rarely present with severe involvement of the abdominal viscera and mesenteric vessels. Severe disease necessitates the use of high dose IV steroids, rituximab or cyclophosphamide, and plasma exchange (PLEX).