I am 17 years old, I have had diabetes for almost three years, and, when I was first diagnosed, my brother was tested to see if he had the genetic marker or trigger for diabetes, which he did. Are there any statistics or results published on the percentage of those who tested positive and have actually developed diabetes? Are there any preventative measures my family should be taking for him?

In very general terms your brother’s chances of getting type�1A (autoimmune) diabetes, which is what I assume you have, is around 5%. However, I think that you are going to have to find out from your doctor precisely what this ‘genetic marker’ is. There are, broadly speaking, two possibilities.

The first is that he had an antibody test which was positive. If this was expressed in JDF units and was the old immunofluorescent test, then depending on the titer, his risk might be as much as 50% of becoming insulin dependent. Recently however this test has given way to another comprising three antibodies: anti-GAD, anti-insulin, and anti-ICA512. Strictly speaking, these are not genetic tests. If only one test is positive, clinical diabetes may be delayed for many years, but if two or three of three tests are positive then insulin dependence will be only a few years away. A positive antibody test in fact indicates that the autoimmune process has begun.

More specific is the HLA pattern of the genes on the long arm of chromosome 6. At the moment though, these only really divide into high risk, neutral, and protective. Not enough people have been tested to allow precise figures for any one pattern, but such figures are being slowly compiled. At the moment, all that can be said is that if your brother shares the identical HLA pattern as yourself, his risk will increase to slightly over 50%.

At the present time the possibilities for deferring or averting insulin dependence are limited. Your brother though might be eligible to participate in the oral insulin part of the National DPT-1 Trial (telephone 1-800-425-8361) or he might talk to his doctor about using nicotinamide, a B vitamin. There is a big trial (ENDIT) of this in Europe which has three years yet to run, but a study in New Zealand school children showed that about 60% of the antibody positive children in the trial could avoid the need for insulin for up to eight years as long as they continued to take the vitamin supplement.

DOB

[Editor’s comment: See Injected Insulin Fails to Prevent Type 1 Diabetes.

SS]