NTHL1 and attenuated familial adenomatous polyposis: In conclusion, the comprehensive investigation of all the five adenomatous polyposis genes in a well characterized Indian FAP cohort confirms the high frequency of APC mutations in classical FAP, MUTYH in AFAP cases and absence of NTHL1, POLD1 and POLE mutations in cases not showing syndromic features of PPAP or NAP.