Endocrine Abstracts

Introduction: Graves’ disease, a common cause of hyperthyroidism, occasionally poses therapeutic challenges. This case report highlights complexities of Graves’ disease management, particularly an unusual complication: Propylthiouracil (PTU) - induced ANCA vasculitis.

Case report: A 51-year-old lady with Graves’ disease diagnosed in 2008, achieved remission with 18 month course of Carbimazole. She experienced a relapse in February 2021 and Carbimazole proved to be ineffective leading to a switch to PTU in May 2022. Twelve months after PTU, she developed recurrent joint pain and intermittent non-blanching vasculitic rash on knees and ankles associated with a rapid decline in renal function and positive ANCA (P+C ANCA), anti-MPO and anti-PR3 antibodies. She had no other features of autoimmune connective tissue disease. Renal biopsy confirmed absence of classical renal vasculitis. Due to her spectrum of presentations, various speciality were involved. A diagnosis of PTU-induced vasculitis was made. Following the replacement of PTU with Carbimazole and immunosuppressant therapy (prednisolone and methotrexate), joint pain and rashes resolved, renal function improved dramatically, and thyroid function improved. Since the complete withdrawal of immunosuppression in October 2023, symptoms of thyrotoxicosis returned with TSH <0.01 mU/l and FT4 >100 pmol/l. Carbimazole dose was up-titrated along with glucocorticoid therapy. She is due to have follow-up in 4 weeks. Total thyroidectomy is considered as a definite therapy once her thyroid function improves.

Discussion: PTU-induced vasculitis is rare and requires a high index of clinical suspicion. Prompt discontinuation of PTU would be sufficient for most case but severe cases might require immunosuppressant therapy.