The prevalence of CRC is low in patients with LS under the age of 25 regardless of genotype, however data from both PLSD and IMRC support the notion that those with the higher penetrance MHL1 and MSH2 variants typically develop CRC earlier in life than their MSH6 and PMS2 counterparts (26, 47), hence the decision by some to begin surveillance earlier for MSH1/MSH2 carriers (Table 2). Here, PMS2 is linked to colorectal carcinoma.