The Lesser-Known Types of Diabetes

MODY, monogenic diabetes, and diabetes insipidus, oh my!



It’s not enough to be diagnosed with diabetes; it’s just as vital to be given the correct diagnosis of the type of diabetes. This isn’t as easy as it sounds. While Type 1 diabetes is rare, there are even rarer subsets of diabetes that can easily be confused for Type 1 or Type 2.

There is a difference between diabetes insipidus and diabetes mellitus. “Insipidus” relates to a disorder in urine production that is unrelated to excess blood glucose. It’s caused by the body not producing a key hormone, vasopressin. Connection to diabetes mellitus? None.

One of the better-known lesser-knowns is Mature Onset Diabetes in (or of) Youth, or MODY, for short. This comes about because of the mutation of a single gene, and it cannot be diagnosed without genetic testing early in life. As the name suggests, the biomarkers for the disorder resemble those of adult-onset, or Type 2, diabetes, but because the disorder manifests itself so early in life, it was routinely diagnosed as Type 1, and thousands of kids went straight to insulin therapy.

Then there’s monogenic diabetes. In 1964, Dr. Stefan S. Fajans, a German-born endocrinologist, first described it as a subtype of Type 2 diabetes in a paper he co-published identifying a genetic marker for early-onset Type 2. (Along the way to this discovery, he’d landed with the 41st Evacuation Hospital at Omaha Beach on D-Day plus 3). In 1991, Dr. Fajans and colleagues mapped the gene responsible for this subset of diabetes at chromosome 20q. Treating physicians and researchers in the UK were also at work on the cause and began a collaboration with the Ann Arbor-Chicago group. Thanks to their hard work, we now know that some 1.2% of all diabetes cases are monogenic, with subtypes attributable to mutations in some twenty-five genes.

These differing definitions may seem academic, but they can sometimes make a huge difference. The documentary Journey to a Miracle – Freedom from Insulin features the story of Jack Matthews of Essex, England, who had diabetes and hard-to-explain developmental delays and cognitive difficulties that made it impossible for him to talk. His mom, Emma, tells of the day that monogenic diabetes researcher Dr. Andrew Hattersley said that Jack’s insulin could be stopped, and an oral medication was all that would be needed for glucose control. Within weeks, Jack started talking, and his learning disabilities began to steadily abate.

With so much variation about diabetes uncovered in such a relatively short span of time, it seems possible that more subsets of diabetes will be discovered. It also makes one wonder how many people who deal with “difficult to control” diabetes might be dealing with a yet-undiagnosed form of the condition.

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Jim Cahill is a senior writer for Insulin Nation and Type 2 Nation. Before turning to writing, he was a lawyer in government and private practice who focused on consumer protection and regulatory law. He can be contacted at jcahill@epscomm.com.