A review of the genetics of type I diabetes

Type I diabetes susceptibility is caused by both environmental and genetic factors, the latter comprising approximately half of the total risk as evidenced by the fact that identical twins have approximately 50% concordance, suggesting 50% of the disease risk is environmental. The human leukocyte antigen (HLA) genes account for approximately half of the genetic risk, as demonstrated by the concordance between HLA identical siblings. Because environmental and genetic differences vary between racial groups, the incidence of type 1 diabetes (TID) differs across the world, being highest in Caucasians. Recent GWAS (genome-wide association studies) studies have suggested there may be up to 50 genomic regions contributing to the non-major histocompatibility complex (MHC) genetic risk contribution. This review presents and discusses the latest research on the MHC and non-MHC genes. Only the non-MHC regions, which have been confirmed in multiple studies and which are considered definite regions of genetic susceptibility, are included in the review.