家族性腺瘤息肉病的遗传病因学研究进展

Genetic Etiology of Familial Adenomatous Polyposis

家族性腺瘤息肉病(FAP)是第二常见的遗传性结直肠癌综合征,多在青春期发病,发病率约1/10000,主要临床表现为大肠中多发的腺瘤性息肉,是一种结直肠癌的癌前病变,如果不予治疗,几乎100%的患者会发展成为结直肠癌。一直以来,FAP被认为是一种常染色体显性遗传疾病,发病由APC基因胚系突变引起。根据临床特点的不同,FAP患者可以分为经典型FAP(CFAP)和轻表型FAP(AFAP)。然而近年来,在一些无APC基因胚系突变的FAP患者中发现了Mut YH基因的双等位基因突变。这种由于Mut YH基因双等位基因突变而无APC生殖突变所引起的临床综合征定义为Mut YH基因相关性息肉病[2](MAP)。MAP为常染色体隐性遗传,是一种特殊类型的FAP。另外,很多研究表明,APC基因的突变位点与结肠腺瘤病的严重程度、癌变的风险程度和某些肠外表现相关。MAP的发现和对FAP基因型-表型相关性的研究,完善了对FAP遗传病因学的认识,对于FAP患者及高危亲属的合理防治和预后具有重要的意义。

Familial adenomatous polyposis（FAP） is the second-most common inherited colorectal cancer syndrome, with a prevalence of 1 in 10,000 individuals. Characteristic features of FAP include development of multiple colonic adenomas beginning in early adolescence, and inevitable CRC in untreated individuals. In the past, familial adenomatous polyposis（FAP） was known to be inherited in an autosomal dominant manner and caused by germline mutations in the adenomatous polyposis coli（APC） gene. According to the differences of clinical features, FAP can be divided into two clinical phenotypes, classical familial adenomatous polyposis（CFAP）and attenuated familial adenomatous polyposis（AFAP）. But recently, biallelic mutations in Mut YH gene have been found among some FAP patients without APC gene mutations. The syndrome associate with biallelic Mut YH mutations is called Mut YH-associated polyposis（ MAP）. MAP is inherited in an autosomal recessive manner. In addition, some researches indicate that the location of the mutation within APC has been associated with the severity of colonic polyposis, the degree of cancer risk, and the presence of some extracolonic features. Identification of MAP and researches on genotype-phenotype correlations of FAP provide more knowledge about genetic etiology of FAP to us, which has significance on reasonable diagnosis and treatment on FAP patients and at-risk relatives, as well as their prognosis.