In FAP syndrome, attenuated forms (AFAP) are caused by low penetrance mutations (missense mutations) in the main APC gene or by biallelic loss of the MYH gene (MAP, MUTYH-associated polyposis with autosomal recessive inheritance), encoding a protein of the Base Excision Repair complex (BER) [5]. The gene discussed is MUTYH; the disease is polyposis.