Cutaneous Thrombosis and ANCA-Positive Vasculitis Associated with Propylthiouracil Therapy

The document reports on a case of cutaneous thrombosis and ANCA-positive vasculitis associated with propylthiouracil therapy in a 29-year-old woman who developed painful erythematous lesions on her lower limbs and nose after starting propylthiouracil for Graves' disease. The patient had a family history of autoimmune thyroid disease and vitiligo. She developed bullae, ecchymoses, and widespread cutaneous necrosis. Investigations showed iron deficiency anemia, thrombocytosis, raised inflammatory markers, and ANCA positivity with a PR3 pattern. A skin biopsy revealed intravascular thrombosis and focal necrotising vasculitis. The patient's propylthiouracil was discontinued, and she was treated with intravenous methylprednisolone and oral prednisolone, as well as full anticoagulation. Debridement and grafting were performed on the necrotic areas of the lower limbs, while the nose lesions resolved without tissue loss. The document highlights that anti-thyroid drugs can trigger ANCA-associated autoimmune diseases, with skin lesions being more common in drug-induced cases than idiopathic ones, and that these cases often have a milder course.