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Contribution of "Constitutional MLH1 hypermethylation" to #LynchSyndrome diagnosis!

Updated: Apr 15

Rita Barbosa-Matos - CGA-IGC Communications Committee 

In this enlightening episode, led by Emma Keel, MS, certified genetic counselor at the University of Chicago Medicine, we had the privilege of engaging with Megan Hoenig MS, MPH, CGC, a certified genetic counselor at the Mayo Clinic. Megan specializes in hereditary oncology testing, bringing a wealth of knowledge and experience to the table.

Our conversation couldn't have been timelier, aligning perfectly with #LynchSyndromeAwarenessDay. In the episode, we discuss the contribution of MLH1 constitutional methylation for Lynch syndrome diagnosis. We also explored disease definitions and mechanisms, current genetic testing guidelines while discussing the open questions in the field. 

“While most cases are what you would consider heterozygous, there are documented cases where an individual is mosaic and most of the time the technology isn’t there to distinguished between the two…and that it is why its called constitutional MLH1 methylation instead of germline”

There are more individuals carrying this epimutation than we currently know. By testing more individuals, we can improve the current knowledge on the prevalence of MLH1 constitutional methylation.  Testing should be consider in molecularly undiagnosed individuals that present a Lynch tumor before the age of 50 years, specially if presenting tumor methylation or MLH1 loss in IHC. It is relevant to point out that most cases are sporadic, so we might not see a significant family history.

The take-home message is that constitutional MLH1 hypermethylation can be a cause of Lynch syndrome, so testing in individuals with clinical criteria is paramount, ensuring they receive the tailored care they deserve.

Listen to the podcast HERE


If you enjoyed this podcast, you may like others from the CGA-IGC Podcast Series (Seasons 3, 4, 5 & 6) presented by the CGA-IGC Education Committee. Or, explore our Expert Approach to Hereditary Gastrointestinal Cancers podcast series (Seasons 1 and 2).

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