Atypical Presentation of Microscopic Polyangiitis with Pericarditis Manifesting as Right-Sided Heart Failure

Microscopic polyangiitis (MPA) is an ANCA-associated vasculitis that affects multiple organs. However, cardiac involvement is rare in these patients. We herein report a rare case of MPA presenting with marked peripheral edema and weight gain due to acute pericarditis with borderline tamponade physiology and possible effusive-constrictive features, resulting in right-sided heart failure. Myeloperoxidase-ANCA was strongly positive, and the patient subsequently developed rapidly progressive renal dysfunction. A renal biopsy revealed pauci-immune crescentic glomerulonephritis, confirming the diagnosis of MPA. This case highlights pericarditis with pericardial compressive syndrome as an atypical initial manifestation of MPA.