Alemtuzumab-Induced Graves' Disease Complicated by Pretibial Myxoedema: A Case Report.

BACKGROUND: Alemtuzumab, a monoclonal antibody targeting CD52, is associated with a high incidence of secondary autoimmune disease, most commonly thyroid dysfunction. Alemtuzumab-induced Graves' disease (AIGD) typically follows a relapsing course and may exhibit atypical or severe phenotypes during immune reconstitution (IR). CASE PRESENTATION: We report a case of severe thyrotoxicosis following alemtuzumab therapy for multiple sclerosis, complicated by the development of thyroid eye disease (TED) and pretibial myxoedema (PTM). Despite escalation of antithyroid therapy, biochemical and clinical control remained suboptimal. Radioiodine therapy was not pursued due to the presence of established orbitopathy. Given persistent severe disease and extrathyroidal manifestations, definitive management with total thyroidectomy was undertaken. RESULTS: Thyroidectomy resulted in rapid biochemical control of thyrotoxicosis. thyroid-stimulating hormone-receptor antibody (TRAb) remained markedly elevated after thyroidectomy, indicating persistent autoimmune activity despite removal of the thyroid gland. CONCLUSION: This case highlights an aggressive and uncommon presentation of AIGD characterised by severe thyrotoxicosis, orbitopathy and PTM. Clinicians should recognise the potential for atypical and refractory disease following alemtuzumab therapy. In selected cases, early consideration of definitive therapy is warranted, particularly when radioiodine is considered unsuitable.