From Atlanta, Georgia, USA:
Our question is regarding the theory behind how one gets diabetes. My son is four years old and has Type 1 diabetes. I have a brother and a first cousin who both have Type 1 diabetes and an uncle who has Type 2 diabetes. On my husband's side he had an aunt who had Type 2 diabetes.
Both my mother and myself were participated in the DPT trial and both of us tested negative. My husband has not participated as of yet.
Could you give a brief overview of how diabetes is passed from generation to generation? Is it true that both parents have to pass the susceptibility to their children but both or one can test negative for the antibody? How about cases when a child develops diabetes but both parents say it is not in the family (that they know of)? This would be very helpful to explain to people who ask!
In Type 1 Diabetes, genetic patterns only confer a susceptibility to diabetes, so that for the autoimmune disorder to develop, some environmental factor is required. Vulnerability seems to be primarily vested in a group of reactive cell surface proteins called the HLA antigens. Many subtypes have been recognised and only a selected few confer susceptibility to Type 1 Diabetes; moreover, some types confer more risk than others. A child who receives a high risk HLA type from both mother and father is the most likely candidate for clinical diabetes; but the condition can develop when the high risk gene comes from only one parent.
Most new onset diabetes develops in children where there is no apparent family history because it is perfectly possible for either or both parents to carry the precipitating gene with no clinical evidence of the problem. Likewise it is possible to have antibodies and have no awareness that you might become diabetic. It is also quite possible to have high risk HLA factors and not to have developed antibodies. There are several studies going in North America and Europe to pick carriers of high risk genes both with and without antibodies to find out if the diabetes can be prevented or ameliorated; the DPT-1 is one of them.
The environmental factors have been poorly identified. Certain fractions of cow's milk have been fashionable targets for some time as have a number of viruses; but specific relationships have not yet been identified.
There are still people who say 'there is no diabetes in our family!' but nowadays such a statement cannot be made without a certain amount of genetic testing.
With Type 2 diabetes, the problem is a little different. The reason is that although the clinical picture and the treatment is rather the same for all cases, an increasing number of genetically distinct entities have come to be recognised. These include the mitochondrial disorders, the three types of Maturity Onset Diabetes in the Young, Type A insulin Resistant Diabetes, Amylin deficiency, and several others. Since there is often no pressure to make a specific diagnosis, which is anyway cumbersome and expensive, patterns of inheritance are less clear for the various subtypes that constitute Type 2 Diabetes.
I hope this gives you a glimpse of a complex and rapidly expanding field.
Original posting 8 Nov 97
Last Updated: Tuesday April 06, 2010 15:08:53
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