RESEARCH DESIGN AND METHODS: 71 children with diabetes mellitus (43 diagnosed before 6 months of age, and 28 diagnosed between 6 months and 3 years of age who were negative for diabetes-associated autoantibodies) underwent genetic testing with a combination strategy of Sanger sequencing, chromosome microarray analysis and whole exome sequencing. They were categorized into four groups according to the age of onset of diabetes (at or less than 6 months, 6 to 12 months, 1 to 2 years, 2 to 3 years) to investigate the correlation between genotype and phenotype.

RESULTS: Genetic abnormalities were identified in 39 of 71 patients (54.93%), namely KCNJ11 (22), ABCC8 (3), GCK (3), INS (3), BSCL2 (1) and chromosome abnormalities (7). The majority (81.40%, 35/43) of neonatal diabetes diagnosed less than 6 months of age and 33.33% (3/9) of infantile cases diagnosed between 6 and 12 months of age had a genetic cause identified. Only 11.11% (1/9) of cases diagnosed between 2 and 3 years of age were found to have a genetic cause, and none of the 10 patients diagnosed between 1 and 2 years had a positive result in the genetic analysis. Vast majority or 90.48% (19/21) of patients with KCNJ11 (19) or ABCC8 (2) variants had successful switch trial from insulin to oral sulfonylurea.