Clinical characteristics of mutation carriers in a large family with glucokinase diabetes (MODY2).

To investigate the prevalence and clinical characteristics of heterozygotes of the glucokinase gene mutations G264S and IVS8+2 in the extended pedigree of two patients with permanent neonatal diabetes as a result of glucokinase deficiency (IVS8+2 homozygosity and IVS8+2/G264S compound heterozygosity). Eighty-eight first, second and third degree family members of the two patients with permanent neonatal diabetes were genotyped. Clinical, laboratory and historical data were collected via chart reviews. Thirty-one IVS8+2 and three G264S heterozygotes were identified. Of these, 18/34 (52.9%) had diabetes and 9/34 (26.5%) impaired fasting glucose (IFG), compared with 1/54 (1.9%) with diabetes and 2/54 (3.7%) with IFG in the non-carrier group. Odds ratio for heterozygotes was 70.4 (95% CI 16.9-293.5 and P < 0.001). Mean body mass index of heterozygotes (> 18 years of age) who had diabetes was 27.1 +/- 2.66, compared with 23.18 +/- 4.72 for heterozygotes with normal glucose levels (P < 0.05). While none of the non-carrier women had gestational diabetes, eight of the 10 heterozygotes developed gestational diabetes. Inheritance of a glucokinase mutation by the fetus from a carrier mother resulted in a significant reduction in birthweight (3600 +/- 570 vs. 2970 +/- 390 grams, P < 0.05). These data support the association between carriage of GCK gene mutations, G264S and IVS8+2, and the development of diabetes, impaired fasting glucose and reduced birthweight. Moreover, in heterozygotes, a clear correlation between body mass index and the development of diabetes was observed. These findings underline the need for surveillance and prevention in individuals at risk.