MODY: A Genetic Diabetes That Affects People From a Young Age

What is Maturity Onset Diabetes of the Young? How is it diagnosed and treated? How does it compare to type 1 and type 2 diabetes?

Maturity Onset Diabetes of the Young (MODY) is a type of diabetes caused by a mutation in one of eleven genes in someone’s DNA. These mutations affect different organs in the body and ultimately make it difficult to regulate blood glucose levels. One such way is by preventing the insulin-producing beta cells in the pancreas from making enough insulin. Unlike type 1 and type 2 diabetes, a person can develop MODY by inheriting one copy of a gene mutation.

MODY is passed down genetically from parent to child and is less common than other forms of diabetes. It affects 1-2% of people in the United States who have diabetes and are under the age of 35; however, this number may be higher because 80% of cases of MODY are misdiagnosed as type 1 or type 2 diabetes. Children have a 50% chance of developing MODY if one of their parents have it. However, mutations can still occur at random and impact a generation in which neither parent carried the mutation.

Key features of MODY:

1. MODY is commonly diagnosed in late childhood to adulthood– typically before age 25 (and rarely after age 35). Neonatal diabetes, also caused by a single gene mutation, is diagnosed in newborns younger than 6 months of age.

2. MODY can be passed down from an affected parent to a child.

3. MODY is not insulin dependent – people who are affected still produce some insulin.

To get an idea of how likely someone is to develop MODY, you can enter their characteristics into this probability calculator.

How is MODY different than type 1 diabetes?

• People with MODY are more likely to have an affected parent.

• The pancreas continues to produce insulin in people with MODY. In type 1 diabetes insulin production is very low or stops entirely three to five years after diagnosis. (This is measured via C-peptide levels in the blood – a marker that shows that the pancreas is still making insulin. Very low/zero levels of C-peptide suggest that a person has type 1 diabetes.)

• Antibodies (proteins used by the immune system) that attack insulin-producing cells are not likely to be present in people with MODY. These antibodies are present in 85% of people with type 1 diabetes at diagnosis. Blood tests can detect antibodies (such as GADA, IA-2A, and ZnTr8) to confirm type 1 diabetes.

How is MODY different than type 2 diabetes?

• MODY has an early age of onset, whereas type 2 diabetes is more commonly diagnosed in people over age 45.

• While MODY is not usually associated with overweight or obesity, someone who is obese with MODY may develop symptoms sooner than someone who is not affected by overweight.

What are the signs of MODY?

The signs of MODY are the same as other kinds of diabetes – thirst, frequent urination, and weight loss, but some types of MODY may not produce any symptoms.

How is MODY diagnosed?

As with all types of diabetes, a healthcare professional will run an A1C blood test to determine your average blood glucose level. Other blood tests can be done to rule out type 1 or type 2 diabetes.

Genetic tests are done if there is a possibility that someone has MODY and is less likely to have type 1 or type 2 diabetes. A genetic test (with a blood sample) can determine a definitive MODY diagnosis.

How can you treat MODY?

There are currently 11 types of MODY caused by mutations in different genes, with the four types (below) being the most common. Treatment options depend on which type of MODY you have, so a healthcare professional will help you develop a plan for managing your blood sugar.

• MODY 1 (HNF4A gene), MODY 3 (HNF1A gene): people with these types of MODY usually oral sulfonylureas (pills) to lower their blood glucose; 30-40% of people will eventually need to also take insulin to keep their blood sugar in-range. 

• MODY 2 (GCK gene) is shown by slightly elevated fasting blood sugar levels that last throughout a person’s lifetime. This type of MODY usually does not require any pills or insulin because it only increases your blood sugar a little bit (and treatment often has no effect). If you are pregnant and have MODY 2, it is important to carefully monitor blood glucose levels and the growth of your baby.

• MODY 5 (HNF1B gene) is rare and is associated with unusual kidney development. People with MODY 5 usually require insulin.

For people with any type of MODY, maintaining a healthy bodyweight by eating a balanced diet and exercising regularly can improve treatment outcomes.

Do you think you might have MODY? Share this article with your healthcare professional.