Background
Familial adenomatous polyposis (FAP), a rare autosomal dominant
inherited disease, is generally considered to be related to the APC gene[1]. However, there is a special type of
APC-negative but MUTYH-positive called MUTYH-associated polyposis (MAP).
MAP includes both monoallelic mutations and biallelic mutations[2]. Of course, biallelic mutations lead to an
increased risk of colorectal cancer. But patients with biallelic
mutations are a minority, and heterozygous variants are more common. It
is still unclear whether only one MUTYH mutation is of clinical
importance or not. Recently, more and more research has focused on the
risk of colorectal cancer caused by monoallelic mutations[3]. Previously, a number of studies showed that
monoallelic MUTYH had little to do with CRC. Whether heterozygous
variants increase the risk of colorectal cancer is still under debate[4]. Interestingly, what happens in the gut
deserves further investigation if there is another mutation associated
with colorectal polyps. In this report, we described the rare genetic
variant, which were unusual genetic mutations that improve our awareness
and understanding of the disease.