When Diabetes is not Type 1 or Type 2 - Monogenic Diabetes

This is an introductory post on Monogenic Diabetes (MD), a form of diabetes that is neither Type 1 nor Type 2. It is caused by a genetic variation (or error depending on your view) which causes abnormalities in blood sugar regulation. MD is technically two types of genetic variations, neonatal diabetes and what is called Maturity Onset Diabetes of the Young (MODY). All the forms of MD are inherent at birth, but MODY typically is first diagnosable in children and young adults, hence the term MODY. In fact anyone can be diagnosed with MODY at any age and it is thought that at least 1-2% of all diabetes cases are MODY, so there might be more than 500,000 people in the US with MODY. MODY was first identified in the 1970s and there are now at least 11 forms of MODY that have been identified. And for many of these forms there are literally dozens of different variations that can lead to the genetic defect.

For years I’ve wondered whether I might have MODY. In the following, I’m going to give more background on MODY and in future posts I’ll discuss my journey leading up to being tested for MODY. It may seem strange that I would obsess about this but the most important thing to remember is that being diagnosed with Type 2 isn’t a specific diagnosis. Type 2 is a diagnosis of exclusion and that actually means that you have “Diabetes of Unknown Causes.” And if you don’t know your specific diagnosis you can mistreated, potentially severely mistreated. And unfortunately 95% of patients with MODY are misdiagnosed as either Type 1 or Type 2. In further posts I’ll tell you about actually getting the tests and eventually I’ll tell you when I hear about the results (which I don’t know yet).

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This hasn’t gotten any responses, my sense is MODY simply isn’t on the radar of most diabetics. It arguably should be, about 10 percent of the population is diagnosed as what you rightly call the “diagnosis of exclusion” that is Type 2 and about half a percent Type 1, and quite a few of those folks would more accurately be diagnosed as MODY.

If I recall correctly, MODY-2 or GCK-MODY, one of the most common MODY subtytpes and the only form of diabetes for which the current clinical consensus is to do nothing to treat it, is thought to affect about 1 in 1000 individuals or 0.1 percent of the general population, and normally misdiagnosed as the early stages of either Type 1 or Type 2, depending largely on whether the person presents as lean or overweight. So a modest but significant slice of those purported Type 1s and Type 2s are actually MODY-2 and on medications like metformin and insulin that a lot of research suggests do nothing for them (while incurring side effects).

Of course, those with MODY-2 appear to have the same risk of more typical T1 or T2, and once nuance I don’t feel like I have a great handle on is how to identify and treat these folks, especially those with MODY-2 and modest T2 “metabolic syndrome” presentations, which if I’m not mistaken may describe your case.

Hope you get your results back soon, very interested to hear about them! And kudos for grappling with these issues in a way that can help others here.

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Thanks niccolo. This blog post is really an introduction to the topic as in the next few days I’ll be posting about what I heard at the ADA Scientific Symposiums on the topic of MODY. Even if it isn’t on most people’s radar it clearly is on ours and I just want to make some effort so that people are aware of it. Having MODY and being misdiagnosed and mistreated does make a difference.

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Perhaps it would be on more people’s radars if it was on more doctors radars and people didn’t have to beg for testing and proper diabetes classification and treatment. We are lucky if we get antibody testing for LADA, I’m auto antibody negative and clearly type unusual but will I ever get MODY genetic tests, probably not. The interest is simply not there, the majority of doctors want to treat diabetics that clearly T1 or T2, those of us in the gray area are often left on our own.

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That is a good point, the doctors are actually the ones that should have these issues on their radar. Hopefully some of the clinicians at the ADA got the message and will take it back to their practice.