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Typecasting: A Primer on Types 1, 2, Gestational, LADA, and MODY Diabetes

When people first learn that I have diabetes, right away they always ask if it's type 1 or type 2. Well, neither. The question underscores the lack of awareness outside the diabetes community of the other varieties - like LADA and MODY diabetes. Because I get asked this question at least once or twice a month, it may be valuable to post a primer on the different varieties of diabetes.

Type 1 Diabetes: An autoimmune condition that damages/destroys the pancreas's insulin-producing cells (called beta cells). People with type 1 diabetes produce little or no insulin, so their bodies can't process glucose for energy. This causes blood sugar to rise. People with type 1 must take insulin to control their blood sugar (hence the nickname "insulin-dependent diabetes.")

Type 2 Diabetes: A condition in which a person either produces insufficient insulin or they are unable to utilize it properly. As a result, glucose in the blood can't enter the body's cells for use as energy, causing blood sugar to rise.

Of note: two mothers of type 1 children recently petitioned the ADA to rename types 1 and 2 to better reflect some of the differences.

Gestational Diabetes: A condition in which pregnant women who have not previously been diagnosed with diabetes present with high blood sugar levels during pregnancy, usually during the third trimester.

Latent Autoimmune Diabetes in Adults (LADA): LADA, sometimes referred to as "Type 1.5" shares characteristics with types 1 and 2. As with type 1 diabetes, LADA involves the destruction of the insulin-producing beta cells by the body’s own immune system. Unlike with type 1, there is a relatively slow progression of beta cell destruction so the need for insulin is not immediate. (For more info about LADA, see this post at the Joslin Diabetes Center.)

MODY - (Maturity Onset Diabetes of the Young): MODY is a monogenic form of diabetes that usually first occurs during adolescence or early adulthood. However, MODY sometimes remains undiagnosed until later in life. A number of different gene mutations have been shown to cause MODY, all of which limit the ability of the pancreas to produce insulin. (Definition from the National Institute of Diabetes and Digestive and Kidney Diseases.)

My version of diabetes is MODY. Since it's monogenic - meaning that a mutation in just one gene causes the disease - MODY clusters in families, occurring throughout multiple, successive generations. The affected gene is dominant, so a person who inherits just one copy of the mutant gene (i.e., from one parent) is likely to be affected. Because I carry a MODY gene, each of my two daughters has a 50% chance of inheriting it. (Yeah, bummer.)

Many people with MODY show no signs or symptoms, thus MODY often goes undiagnosed or is misdiagnosed as type 2. As with all other forms of diabetes, untreated MODY leads to the elevated blood glucose levels which, over time, damage body tissues, nerves and blood vessels. Therefore, the treatment goal for MODY is to minimize complications by keeping glucose levels within a specified range. To date, 12 distinct MODY subtypes have been identified, each with its own characteristics and implications for treatment. The University of Chicago’s Kovler Diabetes Center, a good resource on monogenic diabetes, estimates that 1-5% of Americans with diabetes have MODY.

Which type of diabetes are you dealing with? What should people know about it?

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