The key indications for the relatively rare form of diabetes include younger onset and unclear markers.
A new consensus statement has laid out five indications for when patients should seek genetic testing for monogenic diabetes, a form of the disease which affects less than 5% of people with diabetes.
The statement, which was penned by representatives from the Australian Diabetes Society, Endocrine Society of Australia, Human Genetics Society of Australasia, New Zealand Society for the Study of Diabetes and Royal College of Pathologists of Australasia, was published in the MJA this week.
Although monogenic diabetes only accounts for between 2% and 5% of diabetes cases in Australia, patients with the rarer form respond strongly to very specific treatments.
“Misdiagnosis leads to problems with access to the precision treatment that’s required for this type of diabetes,” RACGP diabetes specific interest network chair Dr Gary Deed told The Medical Republic.
“Some of these diabetes are exquisitely sensitive to medications such as sulfonylureas and may not respond well to therapies for those other types of type one and type two diabetes.”
According to the joint statement, the five indications for genetic testing for monogenic diabetes in adults include:
- diabetes onset before 12 months of age,
- glucokinase (GCK)‐hyperglycaemia phenotype,
- diabetes onset before 30 years of age without markers of type 1 or 2 diabetes,
- syndromic monogenic diabetes phenotype, or
- high probability of monogenic diabetes using validated screening tools.
“[If a patient presents with] diabetes onset before the age of 30 without clear definition of whether it is type one or type two diabetes, you shouldn’t just think of type one or type two – monogenic diabetes should be considered,” Dr Deed said.
“The pathway should commence that if you’ve got a patient with early onset diabetes … before the age of 25 or 30, you probably should seek specialty assessment in addition to your own management of those patients, because it could be overlooked.”
Dr Deed said another take-home message for GPs was to specifically flag on referrals when monogenic diabetes was suspected, because non-GP specialists may also fail to consider it.
Associate Professor Sunita De Sousa, an endocrinologist who co-authored the consensus statement, said some patients with monogenic diabetes are able to safely stop treatment.
“The most common type of monogenic diabetes is GCK-hyperglycaemia, where there is a defect in the glucose sensor, which means that the body just runs at a mildly elevated blood glucose level, sort of indefinitely,” she told TMR.
“It doesn’t get worse. It’s not associated with a clinically relevant risk of complications. It doesn’t generally require treatment or surveillance, apart from the special exception of pregnancy.
“And so that is a great diagnosis to make, because that is someone where you could actually stop diabetes treatments and surveillance safely and spare patients and healthcare system from that burden.”
If monogenic diabetes is suspected, Professor De Sousa said, GPs can consider referring to an endocrine genetics clinic or general genetics clinic.
“The fundamental question for GPs is, ‘when should I suspect monogenic diabetes?’ – and the very easy, all-encompassing answer is just ‘when it doesn’t look like type one or type two diabetes’,” she said.
“If we think someone has type one diabetes, they should have positive autoantibodies, they should have younger-onset disease, they should immediately need to go on insulin, and if they stop insulin for some reason, they develop diabetic ketoacidosis … that’s the typical type one diabetes picture.
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“If they’ve got negative type one antibodies, they can go days without insulin or they’ve never developed DKA, then that should ring alarm bells.
“In type two diabetes, if they’re lean, they’re not from a high-risk ethnicity where you can get type two diabetes at a reasonable BMI or they have some other unusual features that you can’t quite marry up, perhaps they’ve got deafness … then you should think, ‘maybe this is a monogenic form of diabetes’.”
While monogenic diabetes does run in families, a negative family history does not necessarily mean that it should not be suspected, Professor De Sousa said.
Endocrine gene panel testing is not currently funded under the MBS in Australia.
Professor De Sousa said she hoped to see this rectified in the future.
“Who has access to genetic tests becomes inequitable because we don’t have PBS funding or MBS funding as a baseline to make sure that everyone who needs it can have access to it,” she said.
“And in particular, this is a big issue on monogenic diabetes because we know that [patients are] spread across the population nationally, but whether they individuals can actually access endocrine genetic tests like this all depends on whether local centres can offer it through public hospital funding.”
