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From Homestead, Florida, USA:

I have a 14 year old daughter who was diagnosed 10 months ago with a diabetic condition. She is carbohydrate intolerant, and her symptoms include overshooting phenomenon. She is 5 foot, 5 inches tall, and weighs about 119 pounds. She was on Precose [a medication for Type 2 diabetes that might be of some benefit to patients with Type 1 diabetes], but is now controlling her glucose with diet and exercise. She is testing before and after meals, and at bedtime - 3 times a week. The endocrinologists tells us she has one of 2 types of diabetes, either MODY, or the onset of Type 1, and that the testing is necessary because her condition could change at any time. She is having bloodwork done every 3 months, and is tested for the presence of antibodies. Is there another test which can tell us definitively what we are facing?


The determination of antibodies against GAD65, IA-2, insulin, or even the ICA test are definitely useful in differentiating MODY (Maturity Onset Diabetes of Youth) from Type 1 diabetes.

The presence of antibodies would clearly point at Type 1 diabetes. Although a negative test would not necessarily exclude it, over 80% of children developing Type 1 diabetes have antibodies around the time of diabetes onset. Moreover, the lack of antibodies together with the clinical picture of a diabetes controlled only with diet and exercise would suggest MODY.

Another useful test would be to have genetic typing done to investigate the presence of genes associated with MODY, but I am not aware of any commercial or clinical laboratory routinely performing this test. Measuring the first phase insulin release during an IVGTT [intravenous glucose tolerance test] may provide limited help in distinguishing these two forms of diabetes.


Additional comment by Dr. O'Brien:

I have to assume that your daughter did indeed have an abnormal fasting blood sugar or glucose tolerance test with glucosuria on more than one occasion. With negative antibody tests it is unlikely that she has autoimmune diabetes or Type 1A diabetes as it is now sometimes called. She might have Type 1B diabetes. These are children who have a typical onset of diabetes; but who are antibody negative. About half of the new onset cases in African American and Hispanic families have this type; but theoccurrence in Caucasian families is less than 10%. In some there is a chromosomal disorder: the onset however is usually more acute though in time many are able to come off insulin and other medication. From the story I think that if the antibody test is negative the most likelydiagnosis is that she has one of the many variants of MODY2 or glucokinase deficiency, the other two forms of MODY do not usually have quite such amild onset especially MODY3. The list doesn't really end here because intheir earlieststages some of the insulin resistance syndromes could present like this.With no evidence of other problems the very rare mitochondrialdiabetesdisorders are most unlikely.

For the time being you are right in supposing that good control iswhat is important; but I don't think that I should express an opinion onthe frequency of testing without knowing the actual figures for bloodglucose and A1c.

Precise diagnosis is rather a problem at the moment because thereis no central laboratory that is equipped to scan all the possibilitiesand new variants are constantly being described. Moreover the incentive tostart one is small as long as it is unlikely to offer much advantages intreatment. D'OB

Original posting 15 Jul 1998
Posted to Diagnosis and Symptoms


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