Another factor that could explain the association of CD with other autoimmune diseases is a common genetic background, represented by HLA haplotype; in fact, some genes in the region of major histocompatibility complex are involved in multiple autoimmune disorders, such as HLA DQA1 and DQB1 genes that can confer risk to both CD and type 1 diabetes [27]. The gene discussed is HLA-DQA2; the disease is type 1 diabetes mellitus.