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Diabetes Mellitus
Inheritance patterns and prenatal diagnosis
Inheritance patterns
Both types of diabetes run in families and emerge in individuals in whom genetic susceptibility is triggered by environmental determinants. Genetic susceptibility to Type 1 resides largely in the genes encoding the HLA (human leukocyte antigen) molecules of the MHC (major histocompatibility complex) located on the short arm of chromosome 6. Relatives sharing these genes are more likely to develop Type 1 but even in identical twins, only about forty per cent share the disease. Type 1 occurs substantially more frequently in people of European than non-European origin, but its incidence varies greatly between national groups and over the course of time within them. Environmental trigger factors are uncertain.
Identical twins are much more likely both to have Type 2. No single genetic locus for susceptibility has yet been located though in rare subtypes of Type 2, occurring atypically in young people (Diabetes - Maturity Onset Diabetes of the Young), a clear pattern of Mendelian dominant inheritance is seen and, in some, the genetic variant characterised. Environmental determinants include increasing age, central obesity and physical inactivity. Some drugs may provoke glucose intolerance. Intrauterine and early life environment may 'programme' liability to diabetes in adult life.
Prenatal diagnosis
Inapplicable
How is it treated?
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