Maturity Onset Diabetes of the Young (MODY)

For those who think they understand diabetes, here is a question: How many types of diabetes are there? If you said one, two or three, you may be surprised to learn that there are more, each with a unique cause.

We all know about type 1 and type 2 diabetes. Many of us have heard references to type 3 diabetes, a title proposed for Alzheimer's disease. There is also diabetes insipidus, which is a disorder of the kidneys, not the pancreas.

Polygenic Diabetes

Type 1 and type 2 diabetes are polygenic. This means there must be change to multiple genes for diabetes to occur. There are sometimes outside triggers (obesity, for example) that play a part in developing these forms of diabetes as well.

Genes make the blueprints for proteins within the cells. If a gene is not working properly, the protein might not function as needed. The gene mutations that result in diabetes are those that interfere with the production of insulin or with the ability of other cells to utilize insulin.

Monogenic Diabetes

Monogenic diabetes is not a single disease. Rather, it is a rare category of diabetes diseases that develop from mutations to a single gene. Between 1 and 5 percent of all cases of diabetes diagnosed in young people are monogenic – and many of these cases are initially wrongly diagnosed as either type 1 or type 2 diabetes.

The specific gene mutations that can result in monogenic diabetes are many, and most of them impair the ability of the pancreas to produce insulin. Most monogenic mutations are inherited; a few spontaneously develop. As with other forms of diabetes, patients are at risk for damage to many areas of the body, particularly the eyes, nervous system, vascular system and kidneys.

It is estimated that up to 5 percent of all diabetes cases are monogenic. The only sure way to diagnose monogenic diabetes, however, is through genetic testing, which is recommended when there is multigenerational involvement. Diabetes caused by certain mutations responds better to oral insulin than injected. Knowledge of which gene is causing the disease can narrow the choice of possible treatments to the most effective.

Maturity Onset Diabetes of the Young (MODY)

MODY is the most common form of monogenic diabetes. It generally occurs first in adolescence or early adulthood. There are instances, however, where MODY is not diagnosed until much later in life. Often, people with MODY will have few symptoms, and diagnosis is made as the result of findings of hyperglycemia in routine bloodwork.

Because a defective gene in one parent means that any child born to that parent has a 50 percent chance of inheriting the disease, MODY tends to appear in successive generations. When this occurs, all members of the family should be tested for the mutation so that appropriate treatment may be begun if necessary.

Sources: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and University Chicago Medicine Kovler Diabetes Center