Factsheet
Condition:
Diabetes mellitus
Inheritance:
Multifactorial; rare Mendelian forms exist.
Genetic Etiology:
Type 1 diabetes: association with specific HLA haplotypes; polymorphism in insulin gene. Type 2 diabetes: multifactorial, with PPARG gene encoding proliferator-activated receptor-gamma being one demonstrated risk factor. Mendelian disorders referred to as maturity-onset diabetes of the young, due to mutations in GCK gene encoding glucokinase, or other genes involved in control of insulin production or secretion.
Frequency:
Varies with different types and different populations.
Clinical features:
Diabetes mellitus is characterized by lack of production or responsiveness to insulin, resulting in chronic elevation of blood glucose. This leads to multiple complications, including obstruction of small blood vessels leading to blindness, peripheral neuropathy, renal disease, and cardiac dysfunction. Type 1 diabetes is due to autoimmune destruction of islet cells in pancreas; type 2 diabetes is due to insulin resistance, and is highly associated with obesity.
Management:
Type 1 diabetes treated by injection of insulin; type 2 diabetes treated with oral hypoglycemic drugs or insulin; both forms require careful attention to dietary management.
Genetic counseling:
Both forms multifactorial, with empirical data used for counseling.