The average onset age of patients in the T1D group (19.6 ± 9.20 years) was earlier than that of patients in the GCK-MODY (24.1 ± 14.95 years) and HNF1A-MODY (26.9 ± 13.00 years) groups, while the T2D group had a relatively older age of onset (45.3 ± 6.82 years). This evidence concerns the gene GCK and type 1 diabetes mellitus.