Bronchiectasis as the Sentinel Manifestation of ANCA-Associated Vasculitis: A Case Report and Literature Review.

Bronchiectasis in ANCA-associated vasculitis (AAV) is usually attributed to structural damage from established disease. We report a 74-year-old woman with 7 years of culture-negative bronchiectasis, incompletely responsive to corticosteroids, in whom AAV was diagnosed after she developed palpable purpura, haemoptysis, hematuria and acute kidney injury. MPO-ANCA was markedly elevated (250.2 U/mL; reference < 1.0 U/mL) with PR3-ANCA negative. Renal biopsy showed pauci-immune crescentic glomerulonephritis, Berden focal class (one of 14 glomeruli with a cellular crescent). Induction with intravenous methylprednisolone and rituximab produced substantial renal recovery (eGFR nadir 23, stabilizing at 60 mL/min/1.73 m2 at 15 months) and near-complete resolution of the pulmonary consolidations. This case describes an airway-first AAV phenotype. She met none of the trigger features that current guidelines use to prompt autoimmune screening, identifying a diagnostic blind spot in progressive culture-negative bronchiectasis without systemic features.