Conference Coverage

Meet the rare diabetes diagnosis that thrills patients



Liana K. Billings, MD, an endocrinologist at the University of Chicago and the NorthShore University HealthSystem in Skokie, Ill., loves the thrill of letting patients know they have a rare kind of diabetes. “Once you do this once, you don’t want to stop,” she told colleagues in a presentation at the annual scientific sessions of the American Diabetes Association. “I hope you all have the experience of diagnosing someone with MODY. It’s phenomenal.”

Dr. Miriam Udler, Massachusetts General Hospital and Harvard Medical School

Dr. Miriam Udler

Yes, it’s true: There’s a diabetes diagnosis that spawns good feelings like delight and relief. The cause for celebration is a condition known as monogenetic diabetes, also known as maturity-onset diabetes of the young (MODY) if it develops after the neonatal period.

“The reason that getting a diagnosis of MODY can be a ‘good’ diagnosis is because the three most common forms of MODY have gene-specific treatments that typically improve patients’ glycemic control and are less onerous than the treatments patients were previously receiving when they were thought to have type 1 or type 2 diabetes,” explained Miriam S. Udler, MD, PhD, of Massachusetts General Hospital and Harvard Medical School, Boston, in an interview.

Dr. Udler and Dr. Billings spoke to colleagues about monogenetic diabetes in their presentation at the ADA meeting.

Research has suggested that 1%-4% of people with diabetes have the monogenetic form, in which the condition is caused by changes in a single gene. A 2017 British study of 1,407 patients with diabetes reported that “the minimum prevalence of monogenic diabetes is 3.6% of patients diagnosed at age 30 years or younger.”

The study, which tested a screening regimen, also turned up 17 new diagnoses of monogenetic diabetes among the 1,407 patients, doubling the total. The findings reflect an apparent fact about monogenetic diabetes: Physicians often don’t look for it, even though a diagnosis can be a godsend – especially for those who were previously diagnosed with type 1 or type 2 and placed on treatment regimens that are unnecessary at best and harmful at worst. (Diabetes Care. 2017 Aug;40[8]: 1017-25)

Patients with the MODY variant in the GCK gene, for example, “can generally stop all medications because they are not at risk for clinically significant complications of diabetes,” Dr. Udler said. “Patients with HNF1A and HNF4A variants can often be switched from insulin injections to ... a sulfonylurea, which is easier to take than insulin injections, and patients generally have better glycemic control after switching to pills.”

Unfortunately for doctors and patients, it can be complicated and costly to test for monogenetic diabetes. But screening tools are available to help physicians make choices about whether to launch testing in the first place, according to Dr. Udler and Dr. Billings.

There are two forms of monogenetic diabetes – neonatal diabetes, which is diagnosed by age 6-9 months, and MODY, which is typically diagnosed in those aged between 10 and 25 years, noted Dr. Billings.

Reasons to suspect MODY include early onset of diabetes (under 35 years), a family history of diabetes, a lack of obesity, and negative islet-cell antibodies, she said.

Obese patients may also have the condition: A 2017 American study of 488 overweight and obese children and adolescents diagnosed with type 2 diabetes found that 4.5% actually had monogenetic diabetes. (Genet Med. 2018 Jun;20[6]:583-90).

Once a physician suspects MODY, physicians may consult the University of Exeter’s risk calculator. It provides guidance about whether a test is a good idea. Dr. Billings cautioned, however, that the value of a calculator’s estimate of risk is not all-encompassing. “You should never use the calculator by itself as a reason to not pursue your intuition,” she said.

Dr. Udler noted that the University of Exeter calculator has important limitations, such as its reliance on specific genes, its lack of consideration of family history outside of parents, and its reliance on the experiences of white European patients.

As for tests, the University of Chicago and the University of Exeter both offer free genetic testing for neonatal diabetes, Dr. Billings said in her presentation.

Monogenetic diabetes tests in older children and adults are not free. However, Dr. Udler said the tests are often covered by insurance companies whether done for one or more genes.

At least one company offers a direct-to-consumer monogenetic diabetes test, according to Dr. Udler, but she recommended against it, especially in light of a curious online notice that says the test isn’t intended to be diagnostic. “I’m not sure what this would be useful for then,” she said.

For her part, Dr. Billings cautioned that test results may be inconclusive, and tests may offer different answers. She also recommended referring patients to genetic counseling.

Dr. Udler reported a board member/advisory panel relationship with Encompass Bioscience. Dr. Billings reported relationships with Novo Nordisk, Sanofi, and Dexcom.

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