January 21, 2002
Genetics and Heredity
Question from Glen Allen, Virginia, USA:
Since we have no family history on either side of diabetes, the doctors assumed that my 13 year old son (who was diagnosed at age seven) developed type 1 diabetes because of a viral infection at some point. However, yesterday, my 11 year old nephew (my sister’s son) was diagnosed with type 1 diabetes. Is this genetic or is this one of those flukes of nature? Is there any way to find out?
Type 1A (autoimmune) diabetes, which I am assuming is what your son and your nephew have because it is by far the most common form to begin in childhood in North America, is a genetic disorder but one which also has to be triggered by largely unknown environmental factors. The degree of genetic risk can be assessed by what is called HLA typing of cell surface proteins. However, the development of insulin dependence still has to be stimulated by some environmental factor. Early exposure to cow’s milk has been invoked as one of these, but the evidence is contradictory. Viruses (especially Coxsackie B) seem to play a role too, but they probably only hasten the last stages before insulin is needed.
You need to understand too that this kind of diabetes, which is usually confirmed by a positive antibody test at diagnosis, usually develops very slowly over several years. Most new onset cases of this type have no family history, although I would presume that there are high risk HLA genes in either your’s or your husband’s side of the family.