A UK study reports that 22% of patients treated with alemtuzumab developed autoimmune disorders, notably autoimmune thyroiditis, which occurred in 15.7% (Cossburn et al. Neurology 2011; 2011; 77:573-579). Secondary autoimmunity developed most commonly in months 12-18 of treatment and was evident for up to five years. Risk factors included a family history of autoimmune disorders (OR 7.31) and smoking history (OR 3.05).