HLA-C and type 1 diabetes mellitus: Evidence that specific markers in or near candidate susceptibility genes mark susceptibility to type 1 diabetes (T1D) was first obtained by association studies, wherein positivity rates of major histocompatibility complex (MHC) alleles in patients were compared with those in an “ethnically-matched” control population (so-called standard “patient vs. control” association studies) [1,2].