Trait Document

Maturity-Onset Diabetes of the Young (MODY) is a rare type of diabetes that results from a change or mutation in a single gene. People with MODY may be mistakenly first diagnosed with type 1 or type 2 diabetes. This is because MODY, type 1 diabetes, and type 2 diabetes have some symptoms in common. However, there are certain features of MODY that doctors usually do not see in people with type 1 or type 2 diabetes. For example, individuals with MODY typically show signs of diabetes at a young age (before 30 years old); they may have a normal weight; and they may produce some, but not enough insulin (i.e., a hormone that uses or stores blood glucose). Additionally, people with MODY do not usually have antibodies in their blood, like people with type 1 diabetes. People with MODY often have other family members with diabetes.

There are many subtypes of MODY, each from a mutation in a different gene. The subtypes of MODY differ in their symptoms and response to treatment. For example, those with MODY5 often have non-diabetic kidney disease. Individuals with MODY2 usually have stable, mildly increased blood sugars. These sugar levels typically do not cause eye, kidney, or nerve problems. Individuals with MODY1 and MODY3, on the other hand, have sugars that increase over time. These individuals have a higher chance of developing health problems from their diabetes.

Most individuals with MODY have a mutation in a gene involved in one of the pathways that controls how insulin is made in the pancreas or when it is released into the body. Currently, mutations in at least 13 different genes have been found to cause MODY. The most commonly affected gene is the HNF1a gene, which causes MODY3. MODY2, the second most common form of MODY, is caused by mutations in the GCK gene.

MODY can be caused by changes in many different genes, and not all of these genes are known. This means that it is possible to have MODY even if a genetic test does not find a change in a MODY gene. It may also be possible for a mutation in a MODY gene to cause diabetes in some family members, but not in others.

All individuals with MODY need to check their blood sugars on a regular basis. They should have regular eye and foot exams, as well as tests to make sure their kidneys are working properly. Most individuals with MODY2 do not need to take a diabetes medication on a regular basis.

Women with MODY2 are at risk for having high blood sugar during pregnancy, so their babies may need to be watched more closely by obstetricians. Individuals with MODY1 and MODY3 often respond well to a certain class of diabetes medications called sulfonylureas. These medications help the body produce insulin. However, some individuals with MODY1 and MODY3 may still need to take insulin or other diabetes medications.

MODY is inherited in an autosomal dominant pattern. This means inheriting one MODY mutation is enough for an individual to develop MODY. The mutation can be inherited from an affected parent or it can occur brand new (de novo) in an affected child.

The risk to family members depends on whether or not the individual with MODY has a parent affected with MODY. If a parent also has MODY, the risk of having a child with MODY is 50% with each pregnancy. If a parent does not have MODY, the risk of other siblings being affected is very low.

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