Maturity onset diabetes of the young (MODY) is a rare group of inherited diabetes conditions that involve unusually high levels of blood sugar. They result from a change in a single gene. It often appears before age 25.

Diabetes is a group of conditions that impair the body’s ability to produce or respond to the hormone insulin. Insulin is responsible for allowing glucose in the blood to enter cells. It helps maintain a person’s blood glucose levels. When the body cannot produce or effectively use insulin, a person may have high blood sugar, which can lead to health complications.

MODY is a rare type of diabetes that occurs as a result of a genetic change. If a person inherits this genetic change from their parent, they will generally develop MODY before age 25, regardless of their weight, lifestyle, or ethnicity.

In this article, we will discuss what MODY is, its clinical features, and how to manage it.

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MODY is a rare type of diabetes that occurs as a result of a genetic change that limits the body’s ability to produce insulin. As the name suggests, this form of diabetes usually affects children, adolescents, and young adults. It often manifests before age 25.

MODY is a type of monogenic diabetes, which means that it arises from a change in a single gene. It follows an autosomal dominant inheritance pattern, which means that only one copy of an altered gene is necessary to cause the condition.

In most cases, it occurs because a person has inherited the genetic change from a parent, but it can also result from new changes in a gene and occur in people with no family history of MODY.

The estimated prevalence of MODY is 1 in 23,000 children. This group of conditions may account for roughly 5% of all diabetes cases in the United States.

However, because MODY is so rare, some evidence suggests that doctors may mistakenly diagnose 90% of people who have MODY with another type of diabetes. Because there are different types of MODY, it is important to determine which subtype a person has so that they can receive appropriate treatment.

MODY occurs as a result of genetic changes that affect the function of beta cells in the pancreas. These cells are responsible for monitoring changes in blood sugar and responding with sufficient levels of insulin to regulate a person’s blood sugar levels.

As a monogenic condition, MODY often runs in families. This means that if a person has a family member with MODY, they have a higher risk of developing the condition.

Several different gene changes can cause MODY, all of which limit the ability of the pancreas to produce insulin. At present, data suggest that variations in at least 14 genes cause MODY. However, some genetic variations are more prevalent than others.

The four most common types of MODY involve changes in the following genes:

  • HNF1-alpha gene: Also known as MODY 3, this type results from the most common genetic change responsible for MODY. This change affects the function of HNF1-alpha protein, which alters the development of beta cells in the pancreas, making them less capable of producing insulin to help regulate blood sugar.
  • HNF4-alpha gene: Also known as MODY 1, this type impacts a different HNF protein, called HNF4-alpha. Children with this gene change are often have a high birth weight and low blood sugar at birth. As with MODY 3, the changes in this protein affect the development of beta cells and reduce the ability to produce insulin.
  • HNF1-beta gene: This type is also known as MODY 5 or renal cysts and diabetes syndrome. This type affects the beta protein. Individuals with this genetic change often develop kidney problems in addition to diabetes. This change affects beta cell development and results in the formation of cysts in the kidneys.
  • GCK gene: Also known as MODY 2, this type alters the function of the glucokinase protein, which helps beta cells in the pancreas detect blood sugar changes. As a result, the body is less able to produce a suitable amount of insulin to manage blood sugar levels.

Type 1 and type 2 diabetes are the most common types of the condition. They are polygenic conditions, which means they occur as a result of changes in multiple genes. In contrast, MODY occurs because of a change in a single gene.

MODY is a rare condition and may present with slightly different symptoms depending on which type a person has. Therefore, doctors may misdiagnose MODY as either type 1 or type 2 diabetes. A doctor can diagnose diabetes by measuring a person’s blood sugar levels. However, for an accurate diagnosis of MODY, genetic testing is often necessary.

The table below summarizes some differences among the three conditions.

MODYType 1Type 2
Typical age of diagnosisbirth to 251–30after 25
Diabetic ketoacidosis riskvery rarecommonrare
First-degree family historycommonrarecommon
Insulin resistancerarerarecommon
Beta cell antibodiesnegativepositivenegative
C-peptide levelsnormallowhigh
First-line treatmentsulfonylureainsulinmetformin

People living with MODY may experience mild diabetes symptoms. Symptoms of MODY tend to develop gradually and may include:

MODY also has clinical features, which help distinguish it from other types of diabetes:

  • It often develops before age 25.
  • It typically carries from one generation to the next within families.
  • Treatment often involves diet or medication and does not necessarily require insulin.
  • Individuals with the condition often have a moderate, healthy weight.

After presenting with symptoms of diabetes, a person will typically receive a blood glucose test to confirm high blood sugar levels. Depending on clinical features, a doctor may request additional tests to help determine which type of diabetes a person has.

Genetic testing is necessary to diagnose MODY. The MODY diagnostic guidelines recommend genetic testing if a person:

  • receives a diabetes diagnosis before age 25
  • has a family history of diabetes
  • can produce insulin
  • has normal C-peptide results
  • has negative beta cell antibody results

It is important not only to diagnose MODY but also to identify which subtype of MODY a person has. This is because different subtypes can lead to different complications and respond to different types of treatment.

The specific treatment a person receives will depend on which subtype of MODY they have. In some cases, people with certain subtypes of MODY may not require any treatment and may manage the condition with lifestyle and dietary habits.

Most often, people will use oral medications, such as sulfonylureas, to manage their blood sugar levels. These drugs work by stimulating beta cells in the pancreas to produce more insulin. They may also help insulin work more effectively in the body. A person will usually take 1 or 2 pills per day with or shortly before a meal.

In other cases, a person may use other diabetes medications, such as metformin or insulin injections, to help manage their blood sugar.

If a person suspects that they or their child has MODY, it is advisable to consult a healthcare professional. An endocrinologist will be able to diagnose diabetes.

A person may also consider genetic testing for the condition if a person receives a diabetes diagnosis at a young age, there is a family history, and they present with symptoms that are not typical features of other diabetes types.

MODY is a rare group of diabetes conditions. As the name suggests, they typically present in younger people. They occur as a result of a single genetic change that reduces the amount of insulin a person produces.

These types differ from more common types of diabetes, such as type 1 and type 2 diabetes. To receive a diagnosis, genetic testing is necessary to determine which MODY subtype a person has. Treatment differs among the subtypes, but for most, treatment may involve oral medications such as sulfonylureas.