In part 2 of this Exclusive Interview, Lisa Letourneau talks with Diabetes in Control Publisher Steve Freed about genetic testing for monogenic diabetes diagnosis and determining the proper treatment.
Lisa Letourneau MPH, RD, LDN, is a dietitian and diabetes & genetics clinical research manager at the University of Chicago.
Transcript of this video segment:
Freed: So, a patient comes into your office, they have elevated blood sugar, a fasting blood sugar, and A1C, the word monogenic never comes up in that process. They’re usually put on oral medication, if they’re type 2. If they’re type 1, they’re put on insulin. So, what should you be looking for when that patient is going through the different tests, or should there be another test to determine whether it’s elevated not because of obesity but because of genetics?
Letourneau: Yeah. Those are great questions. So, to kind of answer them separately, so clinical features that people can look for, the first one is the easiest and that’s diagnosis age. So, if people were diagnosed with diabetes under the age of one, so under about 12 months of age, we would encourage them to have genetic testing done to determine if they might have neonatal diabetes which sometimes can be treated with other medications besides insulin like oral medications. So, anyone diagnosed under age one should definitely get genetic testing. For people that are diagnosed after age one, there’s kind of a different set of criteria that you can look for. So, things that rule out type 1 and type 2 diabetes are helpful to start with. So, for example, if you have a patient who you might think otherwise would have type 1 diabetes but they were antibody negative at diagnosis, maybe their insulin requirements are pretty low, those might be reasons to think that they could possibly have this condition. If you have a patient who has a type 2 diabetes diagnosis or even pre-diabetes, if they don’t really have an elevated BMI, if they have incredibly stable fasting blood sugars that don’t really ever go above maybe 140 milligrams per deciliter, A1Cs are incredibly stable, and as well as the family history. So, we look for family histories primarily with people diagnosed under the age of 30 or so. So, they should have a linear family history. So, the patient might have diabetes diagnosed under age 30 as well as one of their parents, one of their grandparents, et cetera. So, that’s kind of the clinical features.
Your other question about what type of testing we could do, the only way to diagnose monogenic diabetes for certain is to do genetic testing. So, the problem with that is that it’s very expensive and insurance companies aren’t always willing to cover the cost of it. It’s not always cost effective to perform that testing on patients. And so, a few different groups including ours have looked at what situations make it cost effective. And so, there’s been some papers published on that. But if a patient has enough of a suspicion to think that they may have this condition, then it can be cost effective in some cases to have that testing done.
Freed: So, a parent comes into the office with a young one-year-old and elevated blood sugars, most medical professionals would say most likely, depending upon the A1C, that it’s type 1 diabetes. And they might do genetic testing, they might not. And then, another patient comes in, and I’ve seen this many times, where it’s a thin person with elevated blood sugars and it’s not type 1. They assume it’s type 2. And it isn’t, and yet the treatment for monogenic is completely different in most cases than you would normally treat somebody.
Freed: So, what is the most likely treatment for monogenic?
Letourneau: So, it really depends on what type of monogenic diabetes they have. So, for neonatal diabetes. like I’ve mentioned before. people that are diagnosed usually under six months of age but sometimes under 12 months of age, about half of those patients who have monogenic causes usually have a mutation in one of two genes that responds really well to oral medications like sulfonylureas. And so, that’s nice because they’re really cheap medications and they often have better blood sugars taking those medications than they do taking insulin as well as less hypoglycemia. So, that’s one example of kind of personalized treatment. Some others, so if a person has GCK-MODY, they don’t usually need any treatment at all. We’ve seen a few cases of people with GCK who were misdiagnosed with having type 1 or type 2, including one person who was misdiagnosed as type 1 and on an insulin pump for many years who didn’t need that treatment at all. He was able to come off of his pump entirely once he had a genetic diagnosis. So, it really depends on the type. Some types of monogenic diabetes still require insulin but it just kind of depends on which type is found.