RESUMEN
INTRODUCTION: Several cases of vasculitis associated with antineutrophil cytoplasmic antibodies (ANCA) have been reported in patients treated with synthetic anti-thyroid drugs but only 2 cases have incriminated benzylthiouracil. OBSERVATION: A 36 year-old woman, 3 years after treatment with benzylthiouracil, rapidly developed progressive kidney failure, related to a pauci-immune extra-capillary glomerular nephropathy and necrotic vasculitis lesions. The search for p-ANCA was positive with anti-myeloperoxidase specificity. She was treated with corticosteroids and 6 monthly intravenous pulses of cyclophosphamide substituted by azathioprine. Renal failure and proteinuria significantly improved. However the high level of p-ANCA. CONCLUSION: ANCA vascularities are a rare but serious complication of treatment with synthetic thiouracile-type anti-thyroid drugs. The ANCA must be measured when confronted with a systemic manifestation during treatment.