MATURITY-ONSET DIABETES OF THE YOUNG (MODY)

MODY is a sub-type of NIDDM. It is characterized by an early age of on set and autosomal dominant mode of inheritance. These features, and th e availability of large multigenerational pedigrees, make MODY useful for genetic studies of diabetes. In the large ii-generational RW pedig ree, MODY is tightly linked to genetic markers on chromosome 20q. Affe cted subjects in this family show abnormalities of carbohydrate metabo lism, varying from impaired glucose tolerance (IGT) to severe diabetes . Approximately 30 % of diabetic subjects become insulin-requiring, an d vascular complications occur. MODY is also linked to the glucokinase gene on chromosome 7p and many different mutations associated with MO DY have been identified in this gene. MODY, due to mutations in the gl ucokinase gene, is a relatively mild form of diabetes with mild fastin g hyperglycaemia and IGT in the majority. Clinical investigative studi es indicate that the genetic or primary defect in MODY is characterize d by deranged and deficient insulin secretion and not by insulin resis tance. There are quantitative and qualitative differences in insulin s ecretory defects which differentiate subjects with MODY due to mutatio n in the gene on chromosome 20q from those with glucokinase mutations. These differences correlate with the severity of diabetes between the se two genetic forms of MODY.