Obesity and HLA in multiple sclerosis

Obesity in childhood or adolescence is associated with an increased risk of pediatric-onset and adult-onset multiple sclerosis (MS).1,2 The mechanisms underlying this association are unknown but have been postulated. Obesity is associated with chronic low-grade inflammation, and adipokines modulate immune function.3 Higher body mass index (BMI) is associated with lower blood levels of 25-hydroxyvitamin D in childhood and adolescence,4 and vitamin D insufficiency is associated with an increased risk of MS.5 It is not known whether the risk of MS conferred by obesity varies according to genetic background, but there are interactions between the human leukocyte antigen (HLA) genotype and other environmental risk factors, including Epstein-Barr virus and smoking.6,7