Alpha B-crystallin, encoded by CRYAB gene, is multifunctional, serving as both a major structural protein in the lens and a small heat-shock protein in other tissues in mammals. Alpha B-crystallin may contribute to the transparency and refractive index of the lens. Single nucleotide polymorphisms (SNPs) in the promoter region of CRYAB gene have been associated with in multiple sclerosis. Mutations in the CRYAB gene cause distinct clinical phenotypes including isolated posterior polar cataract, myofibrillar myopathy, cardiomyopathy, or a multisystemic disorder combining all these features. Impairment of alpha-B crystallin dimerization may be relevant to the pathogenesis of these disorders.