Objectives Alemtuzumab is a humanised anti-CD52 monoclonal antibody, effective in treating relapsing-remitting multiple sclerosis (MS). Acquired autoimmune disease (AID) is a recognised adverse event following this treatment and requires regular monitoring for early diagnosis and management. Thyroid disease is one of the most common AID following alemtuzumab. We present 14 cases of alemtuzumab-induced thyroid disease, aiming to review the outcomes for patients with autoimmune thyroid disease.

Methods Patients treated with alemtuzumab through the Gold Coast MS clinic since 2008 were followed with an active surveillance program. All patients with abnormal results on thyroid function tests were included in the analysis.

Results A total of 14/69 (20%) patients developed thyroid disease with average latency period of 18 months following the first dose of alemtuzumab infusion (range 3–54 months). Seven patients (50%) developed hyperthyroidism; of these, two patients underwent thyroidectomy, one has been referred for radioiodine therapy, three patients remain on carbimazole and one became euthyroid without any intervention or medication. Two patients (14%) had transient increase in the thyroid function before developing hypothyroidism which required long-term treatment with thyroxine. Two patients (14%) presented with hypothyroidism (one subclinical). Two patients had transiently suppressed TSH level which spontaneously resolved. One patient who had recurrent hyperthyroidism during two pregnancies, is currently euthyroid on no treatment.

Conclusions Thyroid autoimmune disease following alemtuzumab is common but from all patients with different manifestations, thyroid disease has spontaneously resolved or remained subclinical in about a third of patients. Almost half of the patients are on long term thyroxine replacement. Only a small number of patients have required definitive treatment for hyperthyroidism. There remains a need for the ongoing active monitoring of patients treated with alemtuzumab for the first 5 years and patients contemplating therapy should be advised of these potential outcomes.