Whilst there is overwhelming genetic evidence that established the etiological role of genes such as HNF1A, HNF4A and GCK, recent studies that have investigated variation in genes such as BLK, KLF11 and PAX4 in large population datasets have not supported their role in causing monogenic diabetes73, and these genes were recently refuted as monogenic diabetes genes by the MDEP GCEP. Here, HNF1A is linked to diabetes mellitus.