My 12 year old son was diagnosed last October with type 1 diabetes. His 14 year old brother has had the disease for seven years. I find it unusual for two brothers to have this same problem, yet their older sisters, ages 18 and 21 (same parents) do not. The pat answer from the doctor is that the cause is genetic, however, there is no history of diabetes either in my wife’s or my family and when I challenged this claim when my second son was diagnosed, they hedged. While I understand that knowing the cause will not create a cure, I am frustrated by their lack of knowledge and/or the unwillingness to look me in the eye and simply say “I don’t know what causes diabetes.” Are the underlying causes of type 1 diabetes known? Why did two brothers get it and their two sisters did not?

What we know about diabetes genetically is still somewhat limited. There are genetic links, but they are common genetic markers so that other factors, mostly unknown, seem to be triggers. It is uncommon for two siblings to both have type 1 diabetes but, in large practices with more than 500 children/teens, there are usually four to six such families. If your family were part of a very detailed and expensive genetic family study, it might be determined exactly which genetic markers were present. But, these markers are randomly inherited, so, that may explain why some in a family have diabetes while others do not. The most common markers are on the short arm of the sixth chromosome in the HLA region associated with the DR and DQ loci. There is much research to answer questions such as you pose but still no definitive answers.

As far as triggers of diabetes, in those genetically susceptible, information is also sketchy. Cows’ milk and wheat/gluten antigens and exposure are high on the list of possible culprits as are some very common cold viruses such as coxsackie. But, we do not really understand why some have pancreatic beta cell immune attacks (islitis) and some do not. There is a good chapter about this in Type 1 Diabetes in Children, Adolescents and Young Adults by Ragnar Hanas, M.D. available on this web site or via most bookstores on current knowledge.

There is also a clear increase in type 1 diabetes all around the world, perhaps triggered by obesity, perhaps by other factors not well known. We thought that breast milk feeding might be protective but it now looks like when breast fed, this also means less and later exposure to cows’ milk rather than something protective passed through the breast milk itself. There was some concern about immunizations “causing” more diabetes but this has been rejected by more recent, better designed research studies.

SB