Description:
<jats:p>Maturity onset diabetes of the young (MODY) is a monogenic form of diabetes inherited as an autosomal dominant trait. The second most common cause is GCK-MODY due to heterozygous mutations in the<jats:italic>GCK</jats:italic>gene which impair the glucokinase function through different mechanisms such as enzymatic activity, protein stability, and increased interaction with its receptor. The enzyme normally acts as a glucose sensor in the pancreatic beta cell and regulates insulin secretion. We report here a three-generation nonobese family diagnosed with diabetes. All affected family members presented with mild hyperglycemia and mostly slightly elevated hemoglobin A1c values. Genetic testing revealed a novel heterozygous T → C exchange in exon 8 of the<jats:italic>GCK</jats:italic>gene which resulted in a phenylalanine<jats:sub>330</jats:sub>TTC → serine (TCC)/p.Phe330Ser/F330S substitution.</jats:p>