An Atypical Case of Microscopic Polyangiitis Associated With Myelodysplastic Syndrome and Complete Atrioventricular Block Mistaken for Infectious Pneumonia.

The association between antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis and hematologic malignancy has been previously described and remains a rare phenomenon (although potentially underdiagnosed). We report the case of an 81-year-old patient with myelodysplastic syndrome who was managed for an infectious-appearing pneumonia, which subsequently complicated into complete heart block and severe acute respiratory distress syndrome with a fatal outcome. The final diagnosis is severe hemorrhagic alveolitis due to ANCA-associated vasculitis meeting the criteria for microscopic polyangiitis. This article provides an opportunity to discuss the association between ANCA-associated vasculitis and hematologic malignancies and the adverse prognosis associated with it.