Microscopic Polyangiitis Masquerading as Recurrent Acute Heart Failure in Advanced Chronic Kidney Disease: A Case Report

Background: Microscopic polyangiitis (MPA) is an antineutrophil cytoplasmic antibody (ANCA)-associated necrotizing small-vessel vasculitis. Its initial manifestations are frequently nonspecific, so diagnosis is often delayed, particularly in elderly patients with multiple comorbidities. In advanced chronic kidney disease (CKD), superimposed pauci-immune glomerulonephritis may be overlooked because renal dysfunction is attributed to pre-existing disease. Early recognition is essential, as untreated disease may rapidly become fatal. Case presentation: An 80-year-old man with stage 4 hypertensive CKD, permanent atrial fibrillation on apixaban, heart failure with preserved ejection fraction (HFpEF) presented with recurrent acute pulmonary edema, hemoptysis, and progressive anemia. Initial work-up suggested decompensated heart failure and pneumonia, with only transient improvement on diuretic and antibiotics. Repeated hospitalizations revealed persistent inflammation, worsening renal function, new proteinuria, microscopic hematuria, and anemia requiring transfusions. Despite extensive evaluation, the diagnosis remained unclear until immunological testing revealed strongly positive myeloperoxidase antineutrophil cytoplasmic antibody MPO-ANCA (>134 IU/mL) with negative anti-glomerular basement membrane antibody (anti-GBM). Severe renal atrophy and bleeding risk precluded biopsy, so a clinico-serological diagnosis of microscopic polyangiitis with pulmonary-renal syndrome was made. Bronchoscopy confirmed diffuse alveolar hemorrhage. Rituximab, glucocorticoids, and avacopan were initiated, but the patient developed recurrent diffuse alveolar hemorrhage and fatal mesenteric infarction. Conclusion: This case shows how microscopic polyangiitis may masquerade as recurrent heart failure in patients with advanced CKD, causing diagnostic delay. Recurrent hemoptysis, unexplained anemia, persistent inflammation, and new proteinuria or hematuria should prompt evaluation for ANCA-associated vasculitis even when comorbidities offer an alternative explanation.