Relative role of APC and MUTYH mutations in the pathogenesis of familial adenomatous polyposis.
OBJECTIVE
Familial adenomatous polyposis (FAP) is an interesting model for the study of colorectal tumour. Two genes contribute to the FAP phenotype - APC and MUTYH - but their relative role is still undefined. The objective of this study was to evaluate the contribution of the two genes to the pathogenesis of FAP by means of a series of FAP families.


METHODS
Sixty-one unrelated families with a diagnosis of FAP and a total of 187 affected individuals were evaluated. After extracting DNA, APC and MUTYH genes were sequenced.


RESULTS
In the whole series of patients, colectomy with ileorectal anastomosis was the most frequent surgery, although the number of patients treated by total proctocolectomy and ileoanal anastomosis was increasing. Duodenal and jejunal-ileal adenomas were present in more than half of the patients. Constitutional mutations were detected in 37 of the 45 families (82.2%); there were 33 families with APC and 4 with MUTYH alterations. Age at onset of polyposis and age at surgery were 10-15 years delayed for carriers of MUTYH mutations; cancer at diagnosis was frequent, and extracolonic manifestations were diagnosed in the majority of MUTYH-positive families. MUTYH-associated polyposis showed the horizontal transmission expected for recessive inheritance (at variance with the dominant pattern seen with APC mutations).


CONCLUSIONS
At least two genes are associated with the FAP phenotype. APC mutations account for the majority of cases, while MUTYH mutations can be observed in 10% of patients. There are few but definite differences between APC- and MUTYH-associated FAP, such as age at diagnosis and pattern of transmission.
Pezzi
Annalisa
A
Department of Internal Medicine, University of Modena and Reggio Emilia, Modena, Italy.
Roncucci
Luca
L
Benatti
Piero
P
Sassatelli
Romano
R
Varesco
Liliana
L
Di Gregorio
Carmela
C
Venesio
Tiziana
T
Pedroni
Monica
M
Maffei
Stefania
S
Reggiani Bonetti
Luca
L
Borsi
Enrica
E
Ferrari
Maurizio
M
Martella
Pietro
P
Rossi
Giuseppina
G
Ponz De Leon
Maurizio
M
D011125:Adenomatous Polyposis Coli / Q000235:genetics / Q000473:pathology / Q000601:surgery; D000328:Adult; D017668:Age of Onset; D016009:Chi-Square Distribution; D045647:DNA Glycosylases / Q000235:genetics*; D005260:Female; D017491:Genes, APC; D020022:Genetic Predisposition to Disease; D006801:Humans; D007558:Italy; D008297:Male; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D012307:Risk Factors; D018709:Statistics, Nonparametric
D045647:DNA Glycosylases; C061738:mutY adenine glycosylase