Which type of diabetes is genetic

Is Genetic Testing Useful for Diabetes? Why It Depends on the Form of the Disease

The genetic mutations that cause diabetes involve the proteins responsible for insulin production or the ability of the body to use insulin. Mutations cause the proteins to function improperly. Genetic testing can identify these mutations in certain cases, but the usefulness of the information they provide varies. First, it depends on whether the form of diabetes is monogenic or polygenic.

Monogenic Diabetes

In 1 percent to 4 percent of all diabetes cases, the condition results from mutations in a single gene. In other words, the condition is monogenic. That means you can pinpoint and test for a single gene. (15)

Two of the most common monogenic forms of diabetes are maturity-onset diabetes of the young (MODY), which usually appears during the teen years or young adulthood; and neonatal diabetes mellitus (NDM), which is most common in newborn babies and infants. (15)

MODY

Some forms of MODY result in slightly high levels of blood sugar that remain stable throughout life, resulting in no symptoms (or mild symptoms), and no complications. Other forms may require treatment with insulin or a class of oral medications called sulfonylureas, which increase the release of insulin from beta cells. (15)

There are at least 10 genes that have been linked to forms of MODY, says Scott Weissman, a certified genetic counselor on the faculty of Northwestern Medicine’s Center for Genetic Medicine in Chicago and the founder of Chicago Genetic Consultants, LLC, in Northbrook, Illinois. The most common mutations are found in the GCK gene or the HNF1A gene. (16)

Weissman cites GCK mutations, which he says are responsible for 30 to 60 percent of MODY cases, as examples of why genetic testing can be useful. “Although the individual’s blood work looks like they have type 1 diabetes, with this type of mutation they actually don’t need insulin because it doesn’t make a difference in the treatment of the disorder.” Testing will tell the doctor that they don’t need to take insulin, preventing unnecessary treatments.  Furthermore, their relatives can be tested for the gene and monitored for the development of MODY.

More on Type 2 Diabetes in Young People

NDM

NDM affects up to 1 in 400,000 infants in the United States, generally during the first 6 to 12 months of life. Infants with NDM do not produce enough insulin, and the condition is often mistaken for type 1 diabetes. They tend to be born undersize and grow less rapidly than their peers without NDM. For about half of babies with NDM, the condition is permanent; for the other half, it disappears but can reappear later. Most testing for NDM will look at three genes: KCNJ11, ABCC8, or INS. (15,16)

Most forms of NDM and MODY are caused by autosomal dominant mutations, meaning they can be passed on to children when only one parent carries the gene for the disease. In these cases the parent who carries the gene has a 50 percent chance of having an affected child. (16)