Propylthiouracil-induced anti-neutrophil cytoplasmic antibody-associated vasculitis mimicking Kawasaki disease.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is rare in children and is characterised as necrotising vasculitis predominantly affecting small and medium-sized vessels. Propylthiouracil (PTU), an antithyroid drug, has been implicated in drug-induced AAV. In contrast, Kawasaki disease (KD) is a common systemic vasculitis, typically observed in children, which affects the medium-sized vessels, including the coronary arteries. An 11-year-old girl who developed AAV while receiving PTU therapy for Graves' disease is described. She was admitted to hospital following a 2-day history of fever, cervical adenopathy, cheilitis and papular rash, 3 weeks after an increase in the PTU dose. Despite discontinuation of PTU and the administration of intravenous antibiotic therapy, her clinical condition deteriorated and over the next 2 days she developed severe diarrhoea, conjunctival injection and swelling and redness of the right index finger. Additional findings included liver dysfunction, hydrops of the gallbladder, coagulopathy and urine abnormalities, suggesting glomerulonephritis. She met the diagnostic criteria for KD and received intravenous immunoglobulin (IVIG) combined with prednisolone, with rapid resolution of clinical and laboratory parameters. Peeling of the right index fingertip became evident on Day 12 of admission. Serial ultrasound cardiography demonstrated no evidence of cardiac involvement. A high titre of myeloperoxidase ANCA was detected in the patient's serum on admission, and the titre decreased during the convalescent stage. This case demonstrates that children with PTU-associated AAV may present with clinical features mimicking KD, and that IVIG along with corticosteroid therapy may be effective in treating patients with drug-induced severe systemic AAV.