[Pyoderma gangrenosum associated with anti-proteinase 3 antineutrophil cytoplasmic antibodies (PR3-ANCA) induced by propylthiouracil].

BACKGROUND: Synthetic antithyroid drugs are often used in the treatment of hyperthyroidism, regardless of aetiology. They may cause various side effects, including the development of anti-neutrophil cytoplasmic antibodies (ANCA), ANCA-associated vasculitis, and neutrophilic dermatoses. Propylthiouracil (PTU) is the antithyroid drug most frequently implicated in ANCA-associated diseases specifically involving anti-myeloperoxidase ANCA (MPO-ANCA). To our knowledge, there are no clinical reports describing the association of pyoderma gangrenosum (PG) and anti-proteinase3-ANCA (PR3-ANCA) induced by PTU, with ANCA levels decreasing after antithyroid drug withdrawal.

PATIENTS AND METHODS: A 68-year-old woman was treated with propylthiouracil (PTU) for toxic multinodular goitre. She presented necrotic ulceration of the lower abdomen. The patient's history, physical examination, and bacteriological and histological samples led to a diagnosis of pyoderma gangrenosum. This pyoderma involved ANCA with antigenic specificity for proteinase 3. Withdrawal of PTU and a short course of corticosteroids and cyclosporine resulted in rapid and complete resolution of the pyoderma gangrenosum as well as a decrease in ANCA. No relapse was observed one year after cessation of treatment.

DISCUSSION: We report a case of PG associated with PR3-ANCA induced by PTU, without any demonstrable vasculitis.