Suspicion Is Key: Diagnosing Elusive Cytoplasmic Antineutrophil Cytoplasmic Antibody (c-ANCA)-Positive Vasculitis.

We present a case of a 53-year-old black male with a past medical history of type 2 diabetes presenting with fatigue, generalized myalgias, and unintentional weight loss developed over several months. The patient was diagnosed with cytoplasmic antineutrophil cytoplasmic antibody (c-ANCA)-positive vasculitis. Renal biopsy confirmed antineutrophil cytoplasmic antibody (ANCA) crescentic necrotizing glomerulonephritis. c-ANCA was positive by enzyme-linked immunosorbent assay. Anti-myeloperoxidase antibody was positive. Without paranasal or lung involvement, the diagnosis was made of renal-limited necrotizing and crescentic glomerulonephritis. The patient was treated with rituximab and prednisone therapy.