Susceptibility genes include those within the major histocompatibility complex (MHC) —especially HLA-DR3, DQB1 * 0201 and HLA-DR4, DQB1 * 0302, which are present in > 90% of patients with type 1 diabetes mellitus—and those outside the MHC, which seem to regulate insulin production and processing and confer risk of diabetes mellitus in concert with MHC genes.