Detection of glucokinase gene defects in non-obese Japanese children diagnosed with diabetes by school medical examinations.

We examined children who were diagnosed with asymptomatic type 2 diabetes by school medical examinations to investigate the existence of glucokinase (GCK) gene defects in this group. Among 20 children diagnosed with asymptomatic type 2 diabetes by school medical examinations between 2003 and 2009 at our 2 hospitals, 8 were classified as non-obese type. Among them, we screened 5 children (2 boys and 3 girls; age: 8-13 years) who had mild elevation of fasting plasma glucose (108-134 mg/dL) with slightly high internationally standardized HbA1c levels (6.3-6.9%) at first close examination. Written informed consent was obtained and all families agreed to participate in this study. We found 4 different mutations (G223S, G81C, S336X and T228M) in 4 of the examined children. The blood glucose control levels had not become worse in any children during the 2-6 years follow-up period. The inheritance of diabetes with GCK gene defect was later confirmed in 1 family. These results suggest that GCK gene defects exist in non-obese children who are diagnosed with asymptomatic diabetes by school medical examinations. Cases of diabetes that are caused by GCK mutations may not be as rare in Japanese subjects as previously described and could be found in patients tentatively diagnosed as type 2 diabetes.