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Severe upper gastrointestinal polyposis associated with sparse colonic polyposis in a familial adenomatous polyposis family with an APC mutation at codon 1520.

ABSTRACT: BACKGROUND: Familial adenomatous polyposis usually results in colonic polyposis with hundreds to thousands of polyps, congenital hypertrophy of the retinal pigment epithelium (CHRPE), and variable extracolonic features. Recent reports indicate that patients with distal mutations between codons 1445 and 1578 do not express CHRPE and have a high incidence of desmoid tumours. PATIENTS: The family studied has an unusual phenotype of sparse colonic polyposis but profuse upper gastrointestinal polyposis. Affected subjects do not have CHRPE. METHODS: The protein truncation test followed by sequencing identified a 2 base pair deletion at codon 1520 in the APC gene. This results in a frameshift creating a stop codon 13 codons downstream. RESULTS: This family demonstrates that sparse colonic polyposis but severe upper tract polyposis may be associated with mutations between codons 1445 and 1578. CONCLUSIONS: Study of duodenal and colonic polyps in further cases with mutations in this region is warranted. Such mutations may preferentially cause duodenal adenomas and desmoid tumours as somatic mutations in these tumours also occur in this region, unlike colorectal tumours where somatic mutations occur more proximally. This study emphasises the importance of screening the upper gastrointestinal tract even when the colonic disease is mild.

SUBMITTER: Leggett BA

PROVIDER: S-EPMC1891546 | biostudies-other | 1997 Oct

REPOSITORIES: biostudies-other

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Familial adenomatous polyposis patients without an identified APC germline mutation have a severe phenotype.

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APC gene mutations in Chinese familial adenomatous polyposis patients.

Project description:AimTo study the characteristics of APC (adenomatous polyposis coli) gene germline mutation in Chinese patients with familial adenomatous polyposis (FAP).MethodsAPC gene from 14 FAP families was amplified by polymerase chain reaction (PCR) and underwent direct sequencing to determine the micromutation type. For the samples without micromutation, the large fragment deletion of APC gene was examined by multiplex ligation-dependent probe amplification (MLPA).ResultsThere were gene micromutations in 9 families with a micromutation detection rate of 64.3% (9/14), including 6 frameshift mutations (66.7%), 1 nonsense mutation (11.1%) and 2 splicing mutations (22.2%). Large fragment deletions were detected by MLPA in 2 families. The total mutation detection rate of micromutations and large fragment deletions was 78.6% (11/14).ConclusionThe detection rate of APC gene germline mutation can be improved by direct sequencing combined with MLPA large fragment deletion detection.

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APC transcription studies and molecular diagnosis of familial adenomatous polyposis.

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A novel large germ line deletion in adenomatous polyposis coli (APC) gene associated with familial adenomatous polyposis.

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Project description:We present here a case of attenuated familial adenomatous polyposis (AFAP) with a family history of desmoids and thyroid tumors. This patient had no colonic polyps but did have multiple desmoids. Genetic analysis identified a 4-bp deletion in codon 2644 (c.7932_7935delTTAT: p.Tyr2645LysfsX14) of the adenomatous polyposis coli (APC) gene. In cases with limited numbers of colonic polyps and desmoids, AFAP may be caused by a mutation in the 3' region of APC.

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