Alemtuzumab-related thyroid disease in people with multiple sclerosis is associated with age and brainstem phenotype at disease onset

Background Autoimmune thyroid disease (AITD) occurs in 40%–50% of alemtuzumab-treated persons with multiple sclerosis (pwMS), most of whom will develop Graves’ Disease (GD). Objective To explore contributory factors for alemtuzumab-related AITD in pwMS. Methods A retrospective patient chart review was performed. Results Sixteen out of 52 (30.8%) pwMS developed AITD. GD occurred in 56.3% (n = 9), the majority (n = 7, 77.8%) symptomatic. All but one (85.7%) pwMS with symptomatic GD developed atypical, large and rapid fluctuations in thyroid hormone levels unexplained by effect of anti-thyroid medication alone. All symptomatic GD cases were age ≤32 years when starting alemtuzumab (ɸ = 0.60, p = 0.03). PwMS who started alemtuzumab at a younger age developed thyroid disease earlier (r = 0.51, p = 0.04). PwMS with clinical and radiological evidence of brainstem involvement at onset of multiple sclerosis were 11 times more likely to develop symptomatic GD compared with those with other phenotypes (p