Congenital hypertrophy of the retinal pigment epithelium in familial adenomatous polyposis: Novel criteria of assessment and correlations with constitutional adenomatous polyposis coli gene mutations

Study of diagnostic value of congenital hypertrophy of retinal pigment epithelium in Chinese familial adenomatous polyposis patients

BACKGROUND

Congenital hypertrophy of retinal pigment epithelium (CHRPE) is an important characteristic of familial adenomatous polyposis (FAP) patients. However, more evidence about its sensitivity, specificity, and diagnostic value for FAP is needed to determine whether CHRPE is a reliable marker.

METHODS

Clinical features of FAP patients were investigated using in-person evaluations. Family members of FAP patients were evaluated with an indirect ophthalmoscope to determine whether they had CHRPE. We defined three diagnostic criteria for CHRPE (criteria A, B and C) based on their shape, quantity and size. Those with negative colonoscopy results and gene mutation results were classified as healthy controls.

RESULTS

Of a total of 23 FAP families, 21 families were CHRPE-positive (91.3%). Among those 21 families, 47 individuals had CHRPE, including 33 FAP patients, 9 APC gene mutation carriers, and 5 individuals younger than 18 years who were later confirmed to have FAP. Fifty individuals had no CHRPE (5 FAP patients and 45 individuals without APC gene mutations and colorectal adenoma). The average number of CHRPE lesions per person was 5.81, and CHRPE was located mostly in the posterior pole in the eye fundus; 76.7% of individuals had CHRPE in both eyes. The sensitivity of the three CHRPE criteria ranged from 78.8 to 90.4%, with the highest sensitivity found for criterion A (90.4%), which had a specificity of 100% for healthy controls and sporadic colorectal cancer patients.

CONCLUSION

CHRPE has vital diagnostic and screening value because of its high sensitivity for discovering FAP and APC gene mutation carriers.

Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE) as a Screening Marker for Familial Adenomatous Polyposis (FAP): Systematic Literature Review and Screening Recommendations

Purpose

Familial adenomatous polyposis (FAP) has an almost 100% colorectal cancer risk warranting early detection in gene carriers. This study presents congenital hypertrophy of the retinal pigment epithelium (CHRPE) as a highly specific phenotypical marker for FAP that can be used in screening at-risk individuals. Screening recommendations including morphological subclassification were formulated with supporting literature.

Methods

A systematic literature review with a comprehensive search strategy was conducted using online databases. Manual searches of bibliographies and reference lists were also performed. Studies meeting inclusion criteria were graded with respect to their hierarchy of evidence and strength of recommendations according to the National Health and Medical Research Council (NHMRC) guidelines of Australia.

Results

Almost 4500 participants were analysed across 28 included studies. The mean specificity of CHRPE as a phenotypical screening marker of FAP was 89% (standard deviation (SD); 14) with a mean sensitivity of 79% (SD; 8). The mean prevalence of CHRPE amongst FAP participants; at-risk participants were found to be 76% (SD; 24) and 37% (SD; 21) respectively. Bilateralism and multiple lesion number ≥3 are features highly specific for FAP.

Conclusion

CHRPE was found to be a non-invasive, rapid, early phenotypical screening marker of FAP. Clinical recognition further allows increased gene analysis efficiency. The absence of CHRPE alone cannot exclude FAP. Our screening recommendations provide guidance to clinicians on evidence based CHRPE assessment. We would advocate inclusion of ocular examinations as part of a three-pronged approach, along with endoscopy and genetic testing, for efficient, timely FAP assessment in at-risk individuals.

Torpedo-like lesions in the ocular fundi of Gardner syndrome: hiding in plain view

Background: The coexistence of fundus torpedoes and Gardner syndrome was initially reported in 1989 and 1992 by Gass and Roseman. Gardner syndrome is a dominantly inherited disease characterized by a multitude of potentially lethal gastrointestinal polyps. Over the ensuing quarter century, several publications demonstrated uncommon, but easily recognized, fundus lesions called Torpedo Maculopathy in apparently normal individuals. These fundus abnormalities were thought to be single and isolated without systemic associations. During the same period of time, a variety of nonspecific fundus abnormalities were described in Gardner syndrome, which, in retrospect, included highly specific lesions that closely resembled macular torpedoes and sometimes were indistinguishable from them.Patient and methods: We now report a confirmed case of Gardner syndrome with numerous fundus torpedoes, and carefully analyze the voluminous literature of both Gardner syndrome and Torpedo Maculopathy.Results: We demonstrate shared features of the fundus lesions in both diseases, and hypothesize that they may have genetic as well as ophthalmoscopic similarities in common.Conclusions: We therefore recommend that individuals with classic isolated torpedoes undergo evaluations for mutations in the Gardner gene (Adenomatous polyposis coli) and for the presence of gastrointestinal polyps and other systemic features of Gardner syndrome. We also suggest that apparently normal individuals, who are genetically related to patients with known classic torpedoes, undergo inspection of their fundi for the possible presence of characteristic lesions.

Congenital focal abnormalities of the retina and retinal pigment epithelium

This paper reviews the published literature on a group of developmental disorders of the retina and retinal pigment epithelium which result in focal abnormalities in one or both eyes. They are often asymptomatic, found on routine examination and are generally non-progressive. Some are associated with other systemic abnormalities.

In patients with a positive family history of familial adenomatous polyposis can the condition be diagnosed from the presence of congenital hypertrophy of the retinal pigment epithelium detected via an eye examination: A systematic review

In classic familial adenomatous polyposis (FAP) adenomas become malignant. Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is a retinal pigmented lesion and is the earliest and most common potential extraintestinal manifestation of FAP. This review aims to summarize and analyse all of the published data on CHRPE in patients with classic FAP and then ascertain whether these patients should undergo a relatively cheap and non-invasive dilated fundus examination to screen for CHRPE. Adhering to Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines our database search identified 102 relevant articles of which 13 were selected for further analysis. The percentage of FAP patients with CHRPE was found to be 80.00%, whereas the percentage of at-risk patients with CHRPE was 31.12%. Despite various statistically significant findings, CHRPE alone cannot be used as a surrogate for diagnosing FAP in those with a positive family history. The authors advocate a combined approach of eye examinations, colonoscopy and genetic testing.

APC gene mutations causing familial adenomatous polyposis in Polish patients

Familial adenomatous polyposis (FAP) is a well-known hereditary condition characterised by alimentary system tumours. Tens to thousands of polyps occur in the colon and rectum of the patients. There is a high heterogeneity with regard to the number and time of the occurrence of polyps. The occurrence of FAP is associated with mutations in the APC tumour suppressor gene, which was described in 1991. Since then, many studies have been done to analyse the distribution of mutations in individual populations and to determine the function of the gene and a diagnostic approach to FAP. Here the APC gene was studied with respect to the occurrence of small mutations and large rearrangements in 300 unrelated Polish FAP families. Ninety-seven mutations were identified in 164 families. Out of these mutations, 80 were small mutations, including 58 small mutations that were first identified in the Polish population (42 novel and 16 described previously). An increased frequency of mutation c.3927_3931delAAAGA was observed in 10% of the Polish group. Seventeen large rearrangements were found in 29 families. Out of those rearrangements, 8 repeat rearrangements occurred in 20 families. A problem in fast molecular diagnostics of FAP is a high heterogeneity of mutations in the APC gene. It seems that a multiplex ligation-dependent probe amplification test and searching for small mutations by the use of screening methods at the 5' end of exon 15 and exons 14, 9, 11, 13, 5, and 3, help to improve the molecular diagnostics of FAP in Polish patients.

Extra-intestinal manifestations of familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominantly inherited disorder, which results from a germ line mutation in the APC (adenomatous polyposis coli) gene. FAP is characterized by the formation of hundreds to thousands of colorectal adenomatous polyps. Although the development of colorectal cancer stands out as the most prevalent complication, FAP is a multisystem disorder of growth. This means, it is comparable to other diseases such as the MEN syndromes, Von Hippel-Lindau disease and neurofibromatosis. However, the incidence of many of its clinical features is much lower. Therefore, a specialized multidisciplinary approach to optimize health care-common for other disorders-is not usually taken for FAP patients. Thus, clinicians that care for and counsel members of high-risk families should have familiarity with all the extra-intestinal manifestations of this syndrome. FAP-related complications, for which medical attention is essential, are not rare and their estimated lifetime risk presumably exceeds 30%. Affected individuals can develop thyroid and pancreatic cancer, hepatoblastomas, CNS tumors (especially medulloblastomas), and various benign tumors such as adrenal adenomas, osteomas, desmoid tumors and dental abnormalities. Due to improved longevity, as a result of better prevention of colorectal cancer, the risk of these clinical problems will further increase. We present a clinical overview of extra-intestinal manifestations, including management and treatment options for the FAP syndrome. Furthermore, we provide recommendations for surveillance of FAP complications based on available literature.

Familial adenomatous polyposis in children younger than age ten years: a multidisciplinary clinic experience

PURPOSE

Children with familial adenomatous polyposis have a greater mortality and morbidity in the first decade of life compared with the general population. Some children with a more severe disease phenotype present early with colorectal adenomata and may require colectomy at an early age. We present our multidisciplinary clinic experience with familial adenomatous polyposis in children younger than age ten years at the time of presentation.

METHODS

A cross-sectional analysis was performed on all patients with suspected or confirmed familial adenomatous polyposis presenting in the first decade of life and followed by the multidisciplinary Pediatric Hereditary Polyposis Clinic at our institutions. Analysis included demographics, clinical presentation and course, gene mutation testing, endoscopic-histologic findings, and surgical outcome.

RESULTS

Twenty-two children (11 males) presented with suspected or confirmed familial adenomatous polyposis. Two were discharged from follow-up after negative adenomatous polyposis coli gene mutation testing. The rest underwent annual hepatoblastoma surveillance through age ten years with negative findings. Twelve patients presented with symptoms: six had de novo familial adenomatous polyposis. Seven had gastrointestinal hemorrhage and went on to colonoscopy. Four patients with adenomatous polyposis coli gene mutation at codon 1309 were referred for colectomy before age ten years. Referral to colectomy was earlier in patients with 1309 mutation and with de novo familial adenomatous polyposis.

CONCLUSIONS

Children with familial adenomatous polyposis younger than age ten years may present presymptomatically for disease surveillance. Familial adenomatous polyposis with adenomatous polyposis coli gene mutation at codon 1309 entails a risk of a more aggressive phenotype; early colectomy may be indicated in children harboring this gene mutation.

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) in familial colorectal cancer

BACKGROUND AND AIM

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is a pigmented fundus lesion associated with familial adenomatous polyposis (FAP). CHRPE prevalence has been reported to be increased in subjects with familial or sporadic non-polyposis colorectal cancer (CRC), suggesting that some individuals with non-polyposis CRC have an attenuated form of FAP. Other studies have not confirmed these clinical observations and have failed to identify mutations in the gene responsible for FAP, but the reason for the discrepancy in relation to CHRPE prevalence has not been resolved. We determined the prevalence of CHRPE in subjects without CRC (negative control cohort), subjects with FAP (positive control cohort), and subjects with familial non-polyposis CRC (test cohort).

METHOD

A cohort study consisting of 37 negative control subjects, 9 positive control subjects with documented APC gene mutations, and 36 test subjects with familial non-polyposis CRC but no identified pathogenic APC gene mutation. The diagnosis of hereditary non-polyposis colon cancer was excluded in the test cohort by testing for microsatellite instability in tumour tissue.

RESULTS

None of the 37 people in the negative control group had CHRPE. Five of nine (56%) patients with FAP had multiple CHRPE lesions. None of the 36 subjects in the test cohort had CHRPE lesions.

CONCLUSIONS

Ophthalmoscopy may contribute to risk assessment in families with FAP but not in familial non-polyposis CRC. Care must be exercised when interpreting pigmented fundus lesions because 8-13% of subjects in each of the cohorts had pigmented retinal lesions that were not CHRPE. Bilateral lesions and lesions with a depigmented halo were the hallmarks of CHRPE associated with FAP.

Cancer genetics in primary care

The cloning of two major breast cancer susceptibility genes, BRCA1 and BRCA2, in 1994 and 1995 and the subsequent development of commercial genetic testing has brought hereditary cancer genetics into the public eye. In addition to DNA-based genetic testing, new strategies and treatments have been developed to provide accurate assessment of cancer risk and to reduce the chances of cancer developing in the future. This increasing scientific and public attention has prompted some cancer patients and their families to find out whether they "have the cancer gene" and has placed more responsibility on primary care clinicians to identify people who should be referred for specialized services of hereditary cancer genetics.

Familial Hepatoblastoma and APC gene mutations: renewed call for molecular research

Recent findings have increased our understanding of the molecular mechanisms involved in the pathogenesis of hepatoblastoma and their relationship to the molecular pathology of familial adenomatous polyposis (FAP). Here, we describe hepatoblastoma in siblings who share a gene mutation for FAP inherited from their father. This observation confirms the link between these diseases and has implications for future molecular research. We also raise the question; should other members of 'at-risk' families be screened following a new diagnosis of either hepatoblastoma or FAP?

Transcript dosage effect in familial adenomatous polyposis: model offered by two kindreds with exon 9 APC gene mutations

Analysis of genotype-phenotype correlations in familial adenomatous polyposis (FAP) patients demonstrated that the phenotypic heterogeneity of FAP is partly related to the mutation site. We investigated the molecular basis for the difference in severity of colorectal disease observed comparing FAP patients from two kindreds with neighbouring germline mutations in exon 9 of the APC gene. Patients from one kindred presented with a attenuated form of FAP, characterized by a low number of colorectal adenomas (up to 22). In FAP patients from this kindred, the APC gene mutation was localized at codon 367, in the portion of exon 9 that is alternately spliced. This is expected to result in the splicing-out of the mutation site in a fraction of mRNA molecules and in the residual production of wild-type transcripts from the mutant APC allele. Patients from the other kindred manifested a FAP phenotype characterized by hundreds of colorectal adenomas (320 to > 500). In these patients, the APC gene mutation abolished the donor site of exon 9a, used in both alternately spliced isoforms of the exon. The analysis of the relative levels of mutant and wild-type transcripts in unaffected colonic mucosa demonstrated that the mutant allele was not expressed. The model offered by our FAP patients with neighbouring exon 9 APC mutations supports the view that in addition to the mutation site, the type of mutation and transcript dosage effects contribute to the heterogeneity of disease phenotypes.

Congenital hypertrophy of the retinal pigment epithelium and APC mutations in two Chinese families with familial adenomatous polyposis

PURPOSE

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) exists almost exclusively among familial adenomatous polyposis (FAP) patients with adenomatous polyposis coli (APC) mutations between codon 413 in exon 9 and codon 1387 in exon 15. We investigated the locality of APC mutations in relationship to the occurrence of CHRPE in two Chinese families with FAP.

METHODS

Genomic DNA of available members of two unrelated Chinese FAP families was investigated for sequence alteration in the APC gene by polymerase chain reaction and direct sequencing. All subjects were examined by binocular indirect ophthalmoscopy (BIO) for CHRPE.

RESULTS

A mutation in exon 6, Arg216Stop, was identified in one patient with FAP and CHRPE. An Arg283Stop mutation in exon 8 was found in 5 members in another family; 4 of them had FAP and all had small hypopigmented white lesions, probably a new type of CHRPE.

CONCLUSIONS

We found two mutations, Arg216Stop and Arg283Stop, upstream of codon 413 in FAP patients presenting with CHRPE. Arg283Stop has not previously been reported in such patients. A large-scale study on CHRPE and APC mutations in Chinese FAP patients is required to affirm their inter-relationships and the significance of the hypopigmented white lesions.

APC gene mutations and colorectal adenomatosis in familial adenomatous polyposis

Correlations between germline APC mutation sites and colorectal pathophenotypes, as evaluated by the direct count of adenomas at colectomy, were investigated analysing colectomy specimens from 29 FAP patients carrying one mis-sense (codon 208) and 14 frame-shift or non-sense APC mutations (codons 232, 367, 437, 623, 876, 995, 1061, 1068, 1075, 1112, 1114, 1309, 1324, 1556). The mis-sense mutation at codon 208 was associated with a relatively mild colorectal pathophenotype. The mutation at codon 367, subject to alternative splicing, was associated with attenuated FAP. The mutation at codon 1309 was associated with the profuse colorectal adenomatosis. For 13 mutations, predicted to result in null alleles or truncated APC proteins, we correlated density and distribution of colorectal adenomas with the predicted functional effects of the mutation. The most severe colorectal pathophenotype was significantly associated with the truncating mutation at codon 1309, which is located downstream to the I beta-catenin binding domain but upstream II beta-catenin-binding domain. Mutations between codons 867 and 1114, which affect the I beta-catenin binding domain, as well as mutations occurring in exons 6 and 9, predicted to result in null alleles, were associated with a less severe colorectal pathophenotype. Overall, the highest number of adenomas was detected in the right colon, followed by the left colon, transverse colon sigma and rectum. However, the highest density of adenomas was observed in the left colon, followed by the right colon, sigma, transverse colon and rectum. Colorectal carcinomas, observed in only five patients, were all in the left colon.

Fundus lesions of adenomatous polyposis

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is the most frequent extraintestinal manifestation of familial adenomatous polyposis. Present in 70% of families with familial adenomatous polyposis, CHRPE is a highly reliable and early marker of the disease. Studies over the past 5 years have addressed the histologic characteristics of the pigmented fundus lesions, the definition of universal positive fundus criteria, and mostly the genotype-phenotype correlation. Indeed, the position of the mutation site of the APC (adenomatous polyposis coli) gene on chromosome 5 influences the retinal expressivity because CHRPE is present only if the mutation is located between exons 9 and 15. In CHRPE-positive families, fundus examination is simple, noninvasive, reproducible, inexpensive, and allows early detection of the mutant gene carriers. Knowing the CHRPE status of patients in a family with familial adenomatous polyposis helps to identify constitutional APC mutations. The combination of genetic analysis and fundus examination offers a 100% diagnostic predictability.

Tumores colorretais hereditários

Cerca de 4% a 15% dos tumores colorretais são hereditários e divididos em dois grupos: polipose adenomatosa familiar (FAP) e câncer colorretal hereditário sem polipose (HNPCC). Ambas são doenças autossômicas dominantes, com transmissão vertical, geração após geração, sem preferência por sexo. A FAP tem penetrância praticamente completa, caracterizada por mais de cem pólipos adenomatosos no intestino grosso, que aparecem em geral após a puberdade e se transformam em câncer em todos os casos não tratados, levando o paciente ao óbito em tomo dos 45 anos de idade. Manifestações extracolônicas são comuns, tais como: pólipos em estômago e duodeno, sarcomas abdominais, pigmentação de retina, osteomas, entre outras. A FAP é causada por mutação no gene APC, que está localizado no cromossomo 5q. Seu tratamento é basicamente cirúrgico, com retirada do intestino grosso, podendo-se preservar o reto, se este não apresentar muitos pólipos. O HNPCC tem penetrância em torno de 80% e não apresenta os pólipos benignos como na FAP, que permitem identificar pacientes com o fenótipo da doença. Geralmente, o diagnóstico da lesão colônica é realizado já na fase maligna, em torno dos 45 anos de idade, com preferência para o lado direito do cólon. Pode haver associação com tumores de endométrio na mulher, estômago, pâncreas, entre outros. É causada por mutação em genes de reparo do DNA (hMSH2, hMLH1, hPMS1, hPMS2, hMSH6/GTBP). A colectomia total deve ser realizada em pacientes com câncer de cólon e HNPCC. Se o tumor estiver localizado no reto, a proctocolectomia total pode ser uma opção. Em indivíduos portadores do defeito genético predisponente ao HNPCC, porém, assintomáticos, a indicação de cirurgias profiláticas é controversa. Atualmente, podem-se identificar indivíduos portadores de defeito genético herdado tanto na FAP como no HNPCC. Esses testes baseiam-se no estudo direto dos genes responsáveis pela respectiva doença ou pela proteína produto dos mesmos. É de suma importância uma abordagem multidisciplinar de pacientes portadores de FAP ou HNPCC, pois existe uma preocupação ética muito grande na realização dos testes genéticos de predisposição, considerando suas conseqüências psicológicas e sociais.