CMMRD, like Lynch Syndrome, is a genetic condition that makes it more likely for a person to get certain types of cancer, except this time it occurs when a child has inherited mutated genes from both parents, and the cancer risk is even higher. PMS2 is the most commonly affected gene in CMMRD.
To illustrate this: my mum has one “good” copy of the gene and one bad copy, so I could have inherited her good gene or her bad gene. And the same goes for my dad. My sister inherited both of their good copies, and therefore doesn’t have Lynch Syndrome or CMMRD, and neither do her children. Whereas I inherited both of their bad genes and therefore have CMMRD. We believe my brother, who passed away many years ago, also had Lynch Syndrome or CMMRD.
As many as 1 in every 300 people may have Lynch Syndrome, while the odds of having CMMRD are one in a million – or 0.0001%.
Lynch Syndrome Ireland 