Congenital hypertrophy of retinal pigment epithelium: a sign of familial adenomatous polyposis

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.

A comparison of panoramic radiographic findings in patients with familial adenomatous polyposis and the general population: a multicenter study

OBJECTIVES

Familial adenomatous polyposis (FAP) is a hereditable disorder characterized by early and unremitting development of intestinal polyps and extraintestinal manifestations requiring multidisciplinary surveillance. Herein we describe a multicenter cross-sectional analysis of the dento-osseous radiographic findings of patients with FAP from North and South America.

STUDY DESIGN

Groups I and II included individuals with FAP diagnosed by standard clinical criteria. Patients were paired with age- and sex-matched participants without FAP. Panoramic radiograph of both cohorts, including children and adults, were analyzed.

RESULTS

Of 114 panoramic radiographs, 38 were from patients with FAP, composed of group I (n = 22) and group II (n = 16), and 76 were from matched control participants. Evaluators had excellent agreement on key findings (intraclass correlation coefficient = 0.89). The prevalence of osseous anomalies was higher in adults (75%) than in children (65.4%). Dental anomalies were also higher in children with FAP with a prevalence of 15.4%.

CONCLUSIONS

We describe important and significant differences in the prevalence of dento-osseous anomalies in children compared with adult patients with FAP. These findings warrant careful consideration and may influence multidisciplinary management of the condition. Conversely, the presence of these abnormalities in pediatric dental patients even if not diagnosed with FAP should be borne in mind as possibly indicating de novo or unrecognized disease.

A metabolic switch controls intestinal differentiation downstream of Adenomatous polyposis coli (APC)

Elucidating signaling pathways that regulate cellular metabolism is essential for a better understanding of normal development and tumorigenesis. Recent studies have shown that mitochondrial pyruvate carrier 1 (MPC1), a crucial player in pyruvate metabolism, is downregulated in colon adenocarcinomas. Utilizing zebrafish to examine the genetic relationship between MPC1 and Adenomatous polyposis coli (APC), a key tumor suppressor in colorectal cancer, we found that apc controls the levels of mpc1 and that knock down of mpc1 recapitulates phenotypes of impaired apc function including failed intestinal differentiation. Exogenous human MPC1 RNA rescued failed intestinal differentiation in zebrafish models of apc deficiency. Our data demonstrate a novel role for apc in pyruvate metabolism and that pyruvate metabolism dictates intestinal cell fate and differentiation decisions downstream of apc.

DOI:http://dx.doi.org/10.7554/eLife.22706.001

Colon cancer remains an important problem in healthcare. Cancer researchers are looking for new ways to detect the disease earlier and treat it more effectively. This is challenging because many of the genetic and molecular causes of colon cancer are still poorly understood. Mutations in the gene that encodes a protein called APC are one of the major causes of the disease. The APC protein normally keeps cells from growing and dividing too fast or in an uncontrolled way and is hence referred to as a tumor suppressor. For example, APC induces stem cells in the intestine to develop into specialized cells that keep the gut working normally. Mutations in tumor suppressor genes are common in many cancers.

Other research has shown that cancer cells must reprogram their own metabolism – in other words, all the chemical processes that keep the cell alive – to meet the demands of proliferating rapidly. In particular, recent studies reveal that colon cancer cells produce less of a protein called mpc1, which is involved in metabolism. These discoveries raised the following questions: does APC have an additional role in maintaining normal metabolism in cells by controlling how much mpc1 is produced? Do mutations in the gene for APC lead to colon cancer because they alter the cell’s metabolism?

Sandoval et al. have now discovered a connection between APC and changes in cancer cells that help them to adapt to a new metabolic program. Experiments with zebrafish – a model animal that is now commonly used in the field of cancer biology – showed that APC acts via mpc1 to regulate how the cell uses energy. This regulation goes awry in colon cells that have abnormal APC activity; however, restoring the cell’s metabolism back to normal was enough to induce cells in the intestine to develop properly.

Together, these findings suggest that restoring the normal balance of energy production in colon cancer cells may be an effective way to make the cells behave normally. This hypothesis remains to be tested and, if confirmed, further studies will be needed to determine whether it will lead to new treatments for colon cancer in humans.

DOI:http://dx.doi.org/10.7554/eLife.22706.002

Oral manifestations in patients with familial adenomatous polyposis: A systematic review and meta-analysis

BACKGROUND AND AIM

The oral manifestations of familial adenomatous polyposis (FAP) have been reported in the recent literature. Therefore, there has been growing interest in the characterization of the dento-osseous anomalies because they may precede colorectal cancer and may be used as a diagnostic marker. This systematic review and meta-analysis was performed to evaluate the published evidence for what are the oral manifestations of FAP and their frequency in affected individuals.

METHODS

The search was performed at Cochrane Library, EMBASE, LILACS, PubMed, Scopus, and Web of Science for articles published up to March 2015. A grey literature search was conducted through Google Scholar. Reference lists of the included articles and additional studies identified by expert were screened for potential relevant studies. The methodology of selected studies was evaluated using the risk of bias checklist of the Agency for Healthcare Research and Quality.

RESULTS

Twenty observational studies totalizing 1635 individuals affected by FAP met the inclusion criteria. Osseous, dental, and oral mucosa alterations were observed in FAP patients. The meta-analysis showed the frequency of osseous jaw lesions, and the dental anomalies were 65.35% and 30.48%, respectively, and two studies suggested that oral mucosa vascular density is a phenotypic manifestation in patients with FAP. Most of the studies were evaluated as moderate risk of bias.

CONCLUSION

The most frequent oral manifestation on FAP patients is osseous jaw alterations. In the future, well-designed studies are necessary to classify osseous and dental anomalies in order to demonstrate the true prevalence of each alteration separately.

Congenital hypertrophy of retinal pigment epithelium (CHRPE) in patients with familial adenomatous polyposis (FAP); a polyposis registry experience

BACKGROUND

Familial Adenomatous Polyposis (FAP) is an autosomal dominant condition giving rise to multiple adenomatous polyps in the colon which invariably become malignant by the fourth decade. Congenital hypertrophy of retinal pigment epithelium (CHRPE) is one of its extra intestinal manifestations early in childhood seen, present in 90% of FAP population and is easy to detect.

FINDINGS

Patients diagnosed with FAP and at risk first degree family members were screened for CHRPE using a slit lamp and indirect ophthalmoscopy. The retina of 17 diagnosed FAP patients and 13 individuals at risk were examined. The site and size of CHRPE lesions were documented. Thirteen (76%) of 17 FAP patients (male-10, female - 7, median age - 30 years; range 15-55 years) had CHRPE lesions; seven (54%) had bilateral CHRPE lesions and six (46%) had unilateral lesions. A single lesion was detected in 6 (46%) while 7 (54%) patients had multiple lesions. Of 13 at risk individuals (7- male, female-6 ; median age 34; range 16-52 years), one was positive for CHRPE and 12 were free of retinal lesions. The sensitivity of the presence of a CHRPE lesion in association with colonic polyps in FAP was 76%, specificity 92%, positive predictive value 93%, and negative predictive value 75%.

CONCLUSIONS

This study found a high sensitivity and specificity for a CHRPE lesion to be associated with colonic polyps of FAP and hence a useful screening method in a burdened health-care system. The method is minimally invasive and simple and would be of particular value in screening children at risk for FAP.

Familial adenomatous polyposis: The practical applications of clinical and molecular screening

Familial adenomatous polyposis (FAP) is an autosomal dominant condition mostly due to a mutation of the APC gene on the chromosome 5q. Carriers have an almost 100% chance of developing colorectal cancer after having multiple (typically 100s to 1000s) of adenomatous polyps. It is usually readily identified through this phenotype of multiple adenomas. Correlations between the location of the family-specific mutation on the APC gene and clinical manifestations of the disease are of some assistance in clinical management, though there is heterogeneity in clinical course even between family members with the same mutation. FAP is important to recognize, as there are disease-specific management implications with respect to offering mutational analysis of the APC (and perhaps other) genes for predictive testing of other family members, endoscopic diagnostic procedures, surveillance planning, and surgical management. Extra-colonic manifestations, including duodenal polyposis, desmoid disease and other tumours, can dominate clinical care after colectomy. The inheritable and lethal nature of the disease, together with the availability of effective treatment strategies, makes a sensitive clinical and psychosocial approach important to maximize compliance and good outcomes for all members of affected families.

Dento-osseous changes as diagnostic markers in familial adenomatous polyposis families

BACKGROUND

We have previously described a weighted index for determining the diagnostic significance of dento-osseous changes observed on dental panoramic radiographs (DPRs) in individuals at 50% risk of inheriting Familial Adenomatous Polyposis (FAP). A diagnostic test based on this index (Dental Panoramic Radiograph Score, DPRS) was shown to have a sensitivity of 69% and specificity of 100%.

OBJECTIVES

To evaluate the validity of the diagnostic test in an independent sample of individuals at 50% risk of inheriting FAP.

DESIGN

A retrospective assessment of DPRs in individuals at 50% risk of inheriting FAP.

SUBJECTS AND METHODS

A final year dental student assessed blindly and independently, DPRs from an independent sample (n = 119) of affected (n = 26), unaffected (n = 78) and clinically low risk individuals (n = 15). This revealed a sensitivity and specificity of 62 and 97% respectively which is in close agreement with results of the previous study. The dental student's training in assessing DPRs was previously tested using radiographs from 81 individuals from our original study. Weighted Kappa statistics were used to test for agreement. A kappa score of 0.82 (95% confidence interval 0.70-0.93) indicated almost perfect agreement.

MAIN OUTCOME

The DPRS is a reproducible and valid index for assessing the diagnostic significance of dentoosseous changes, in individuals at 50% risk of FAP, even in relatively inexperienced hands.

Gardner-associated fibromas (GAF) in young patients: a distinct fibrous lesion that identifies unsuspected Gardner syndrome and risk for fibromatosis

Gardner syndrome (GS), caused by mutations in the adenomatous polyposis coli (APC) gene, is characterized by polyposis coli, osteomas, and various soft-tissue tumors. If undetected or untreated, virtually all patients develop colonic carcinoma at a young age. Early detection, while essential, can be difficult because of attenuated phenotypes or spontaneous mutations. We present the clinicopathologic features of 11 identical fibromatous lesions that we have termed Gardner-associated fibroma (GAF), which not only appear to be a part of the spectrum of lesions associated with GS but, in some cases, represent the sentinel event leading to its detection. The GAFs occurred in 11 patients (5 boys and 6 girls; age range, 3 months-14 years), were solitary (n = 7) or multiple (n = 4), and occurred in the superficial and deep soft tissues of the paraspinal region (n = 7), back (n = 3), face (n = 2), scalp (n = 2), chest wall (n = 2), thigh (n = 1), neck (n = 1), and flank (n = 1). Histologically, GAFs resemble nuchal-type fibromas (NFs), consisting of thick, haphazardly arranged collagen bundles between which are found occasional bland fibroblasts, and having margins that frequently engulf surrounding structures including adjacent fat, muscle and nerves. After surgical excision, four patients developed recurrences that were classic desmoid fibromatoses (DFs). In one patient with multiple GAFs, one lesion had the features of GAF and DF in the absence of surgical trauma. A family history of GS or polyposis (n = 6) or DF (n = 1) was known at the time of surgery in seven patients. In three patients, the diagnosis of GAF resulted in the diagnosis of unsuspected APC in older family members, with the detection of an occult colonic adenocarcinoma in one parent. In the family of the remaining patient, no stigmata of GS were present. Genetic analysis of this child was performed to investigate the presence of a spontaneous (new) mutation; however, no abnormalities were detected. The significance of GAF is that it serves as a sentinel event for identifying GS kindreds, including those with a high risk for the development of DF, and it may potentially identify children with spontaneous mutations of the APC gene. Because NFs and GAFs resemble one another, we suggest that a subset of NF occurring in multiple sites, unusual locations, or children may be GAF.

Diagnostic value of fundus examination in familial adenomatous polyposis

BACKGROUND

Multiple, bilateral lesions of congenital hypertrophy of the retinal pigment epithelium (CHRPE) have been described in patients suffering from familial adenomatous polyposis (FAP) since 1980. This study aimed to determine a reliable diagnostic criterion, based on the size and number of retinal CHRPE lesions, allowing the screening of patient carriers of the gene responsible for FAP.

METHODS

32 control subjects and 144 patients belonging to 85 FAP families were studied, divided into 124 carriers of the genetic alteration and 20 non-carriers.

RESULTS

In carriers of the deleted gene, multiple, bilateral retinal lesions were consistently observed. Lesion situation, size, shape, and degree of pigmentation were variable however. A positive criterion for FAP was defined as the presence of at least four lesions whatever their size, or at least two lesions one of which is large. This criterion showed a high sensitivity (0.68) and a maximal specificity (1). Within each family, the retinal phenotypic expression was homogeneous. CHRPE lesions were observed in two thirds of the FAP families and absent from the remaining third.

CONCLUSION

By using this new positive diagnostic criterion, fundus examination allows early detection of those children carrying the gene responsible for FAP in families positive at ocular examination.

Extracolonic features of familial adenomatous polyposis in patients with sporadic colorectal cancer

We have investigated the occurrence of attenuated extracolonic manifestations (AEMs) of familial adenomatous polyposis (FAP) in patients with non-polyposis colorectal cancer. In a prospective case-control study, we observed that significantly more colorectal cancer patients exhibited AEM than did age and sex-matched controls (19.5% vs 7.5%, P < 0.004). However patients with AEMs do not have occult FAP, as we found no heterozygous adenomatous polyposis coli (APC) gene mutations despite extensive analysis of constitutional DNA. Genome-wide DNA replication errors (RERs) occur in a proportion of colorectal cancers, particularly right-sided lesions and in almost all tumours from hereditary non-polyposis colorectal cancer (HNPCC) patients. As AEMs have been reported in familial colon cancer cases, we investigated the relationship of AEMs to tumour RER phenotype. There was indeed an excess of AEMs in patients with right-sided tumours (30.2% of 53 patients vs 14.7% of 116 patients, P < 0.03) and in those with RER tumours (3 out of 12 patients with RER tumours vs none out of 21 patients with non-RER tumours, P < 0.05). Two patients with AEM were from HNPCC families compared with none of those without AEM (P < 0.05). The association of AEMs with colorectal cancer is intriguing, and we speculate that it may be a manifestation of mutational mosaicism of the APC gene, perhaps associated with a constitutional defect in DNA mismatch pair.

Florid oral manifestations in an atypical familial adenomatous polyposis family with late presentation of colorectal polyps

Early identification and prophylactic surgery are essential in preventing development of malignancy in colorectal polyps in familial adenomatous polyposis (FAP). Previous studies indicate a 100% cumulative risk of developing colonic polyps in individuals with FAP by the age of 34 yr. However, we have previously reported late-onset and non-penetrance of polyposis in four families. We describe here in detail one of these families with florid oral manifestations detectable on panoramic radiography of the jaws, which were instrumental in the diagnosis of FAP in the index patient and for ascertainment of her family for screening. The pathological adenomatous polyposis coli (APC) gene mutation in this family was shown to segregate with dento-osseous changes. Panoramic jaw radiography is a common examination carried out prior to dental or oral surgical procedures. This case illustrates the importance of appropriate investigations, including family history and colonoscopy, even in relatively older patients with radiological findings such as those described here and in members of their families at risk of FAP.

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) and familial adenomatous polyposis (FAP)

Familial adenomatous polyposis (FAP) is a genetically transmitted disease affecting the colon. It is characterized by the presence of several (at least 100) adenomatous polyps, each able to develop into carcinomas, and by other extra-colonic signs such as skin and bone lesions. Within the framework of research studies to identify phenotyphic markers for early detection of subjects at risk within a family affected by FAP, attention has recently been paid to congenital hypertrophy of the retinal pigment ephitelium (CHRPE). With the aim of evaluating the relationship between FAP and CHRPE, 36 members of 7 FAP families were examined. We found that 43.75% of the subjects presenting CHRPE areas were also affected by FAP, whereas 58.33% of patients affected by FAP had CHRPE. Our findings indicated a lower incidence of CHRPE in FAP patients, compared to other studies reported so far. Moreover, in a control group of 160 healthy individuals we found a CHRPE prevalence of 5.5%.

Molecular genetic basis of colorectal cancer susceptibility

The past decade has seen considerable advances in understanding of the molecular processes involved in the development of colorectal cancer. With an increased awareness of genetic aspects of the disease there have already been significant changes in clinical management. This is exemplified by familial adenomatous polyposis, where identification of mutations in the adenomatous polyposis coli (APC) gene in affected individuals can be used directly to reduce the requirement for clinical screening in at-risk relatives. In other more common but less well defined heritable forms of colorectal cancer, testing to identify individuals for early diagnosis and treatment will soon become routine practice. This review does not set out to discuss all aspects of the molecular genetics of colorectal cancer but concentrates on the roles of the APC gene and the recently discovered DNA mismatch repair genes in colorectal cancer. The identification of these genes and their functional significance in the neoplastic process is discussed, and the relevance of such discoveries to future research and clinical management explored.

The dental phenotype in familial adenomatous polyposis: diagnostic application of a weighted scoring system for changes on dental panoramic radiographs

A weighted scoring system (Dental Panoramic Radiograph Score) taking into consideration the nature, extent, and site of osseous and dental changes on dental panoramic radiographs in familial adenomatous polyposis is described. The weighting takes into consideration the incidence of the anomaly in the general population. The reliability of the system was tested by application to 85 people known to be affected by clinical or mutation analysis, 30 people lacking mutation in the adenomatous polyposis gene, and 19 people shown to be at low risk (< 1%) by linkage analysis. Using the highest thresholds, a specificity of 100% and sensitivity of approximately 68% was obtained. If all positive findings were considered as significant, sensitivity was increased to approximately 82% but the specificity was reduced to approximately 88%. Significant DPRS findings were observed at a significantly higher frequency in patients aged over 20 compared to the patients aged 20 and under. Overall, approximately 68% of the affected subjects had significant changes, and approximately 18% had normal appearance on DPR, with the remainder having changes classified as minimal or equivocal.

Novel germline APC gene mutation in a large familial adenomatous polyposis kindred displaying variable phenotypes

The APC gene is mutated in the germline of people from families where there is a predisposition to develop polyposis coli. Many mutations have been described but the relation between their site and the phenotypic expression of the disease remains unclear. The most commonly seen mutation occurs at codon 1309. Many other mutations have been described towards the 5' end of exon 15 of the APC gene but comparatively few have been seen towards the 3' end. Recent reports have indicated the possibility of a functional boundary with respect to severity and age of onset of disease, which lies towards the 5' end of the gene. This report describes a large family whose affected members present with a very variable phenotype ranging from an early onset and severe form to a comparatively mild later onset one. The mutation that predisposes to disease in this family is at a previously undescribed site that lies towards the 3' end of exon 15 of the APC gene, which results in a stop codon. Interestingly, the stop codon is 63 codons downstream of the mutation and therefore may affect the expression of the disease. The addition of this mutation to the growing list of mutations described in the APC gene may provide some insight into the genotype/phenotype relation of the disease thus contributing to the understanding and significance of mutations at specific sites in the APC gene.

Familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant condition resulting in the development of more than 100 adenomatous polyps in the large bowel. In addition, a number of extracolonic manifestations of the condition may occur. Recently, increasing knowledge relating to the extracolonic abnormalities, and localization and sequencing of the gene for FAP, have had important implications for screening and long-term follow-up of those affected. In this review the natural history of the disease and the extracolonic manifestations associated with it are considered. Surgical management and advances in understanding at a molecular level are discussed, as well as the problems relating to screening for FAP and the implications of the new knowledge.

Congenital hypertrophy of the retinal pigment epithelium and mandibular osteomata as markers in familial colorectal cancer

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) and multiple mandibular osteomata are markers of familial adenomatous polyposis (FAP). We have assessed their prevalence in non-polyposis familial colorectal neoplasia. Multiple mandibular osteomata were present in 1/29 (3%) patients with familial colorectal neoplasia. CHRPE was present in 11/33 (33%) patients with familial colorectal neoplasia compared with 3/36 (8%) with sporadic disease (P = 0.01) and 4/32 (12.5%) control subjects (P = 0.04). Seven patients with familial colorectal neoplasia had multiple areas of CHRPE compared with one with sporadic disease (P = 0.02) and one control subject (P = 0.02). There was no obvious correlation between calculated familial colorectal cancer risk and the presence of multiple areas of CHRPE. A proportion of patients with familial colorectal cancer have a marker found in FAP and may therefore have a constitutional genetic defect, at least in part responsible for their cancer, making them an interesting group for genetic study. Ophthalmoscopy may contribute to risk assessment in familial colorectal cancer.

Changes in the retinal pigment epithelium close to retinal vessels in familial adenomatous polyposis

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) is known to occur in patients with familial adenomatous polyposis. Its relation to the course of the retinal blood vessels is emphasized in this publication. A 15-year-old girl with familial polyposis coli showed a longitudinal strip of whitish change following the course of a superior nasal artery of the left eye, falsely appearing to enclose the blood vessel like a sheath. A 34-year-old woman from another family with polyposis coli also showed a longitudinally orientated area of hypo- and hyperpigmentation close to temporal retinal veins. Two further patients revealed hyperpigmentation of the RPE under retinal vessels. It is hypothesized that these changes indicate an effect of the hypo- and hyperpigmentations of the RPE on the development of retinal vessels. In four patients, multiple dotlike hyperpigmentations were found in the extreme periphery of the retina; however, the bigger patchy hyperpigmentations were predominantly located in the midperiphery of the retina.

The role of congenital hypertrophy of the retinal pigment epithelium in screening for familial adenomatous polyposis

Retinal examination by indirect ophthalmoscopy was performed on seventy members from 20 kindreds demonstrating the clinical manifestations of familial adenomatous polyposis and forty controls. Thirty-four of 43 affected patients manifested CHRPE lesions compared with 2 of 27 at risk and 2 of 40 controls giving a sensitivity of 79% and specificity of 95% based on the control group. The difference between the affected and at risk groups was significant (Chi-squared = 34.098, 1 df, P = 0.001). The low sensitivity and variation in incidence of CHRPE in FAP patients and general population documented in the world literature prevent its use as a sole marker for the condition. With advances in knowledge of the disease at a molecular level it is now possible to alter risks for families by DNA analysis. There remain a number of patients in whom such techniques do not significantly alter risks. In these families by combining the results of DNA analysis, sigmoidoscopy and retinal examination it may be possible to alter risks by a significant degree. Retinal examination should be reserved for those families in whom risks cannot be altered sufficiently by DNA analysis alone.

Genetic heterogeneity of congenital hypertrophy of the retinal pigment epithelium (CHRPE) in families with familial adenomatous polyposis

One hundred and eighteen subjects with familial adenomatous polyposis (FAP) and 80 of their relatives who were at low risk (< 0.01) of carrying the FAP gene were scored by one of us (BJ) or by colleagues to assess the frequency of congenital hypertrophy of the retinal pigment epithelium (CHRPE). A CHRPE is defined as an "oval pigmented lesion surrounded by depigmented halo". Seventy five (63.6%) of the FAP cases and one (1.2%) of their relatives had at least one CHRPE. There was no systematic difference in the number of CHRPEs in the left and right eyes so all analyses are based on total number of CHRPEs and the findings were highly correlated (p = 0.001 for a test of no correlation). There was also no evidence of any age effect in total number of CHRPEs in affected subjects. In 26 families there was more than one subject affected with FAP. There was a significant common family effect with respect to CHRPE expression for total number of CHRPEs with an F statistic of 1.73 (p = 0.02 for a test of no family aggregation) indicating that family members are more similar to each other than to affected subjects from other families. This may indicate that specific mutations play a role in determining the number of CHRPEs. Nine affected subjects had intra-abdominal desmoids, and in these the frequency of each of the types of CHRPE was no higher (in fact, slightly lower) than the average for affected subjects without desmoids, but this difference was not significant (p > 0.3).

Assessment of the value of congenital hypertrophy of the retinal pigment epithelium as an ocular marker for familial adenomatous polyposis coli

The presence of bilateral, multiple patches of congenital hypertrophy of the retinal pigment epithelium (CHRPE) is cited as an early phenotypic marker of the familial adenomatous polyposis coli (FAPC) gene. However, the degree of concordance between CHRPE and the presence of familial adenomatous polyposis (FAP) has not been adequately assessed in individual families. We studied the eyes of 28 members of a single kindred spanning three generations with FAPC; 14 were affected and 14 unaffected but 'at risk'. Six affected and 8 unaffected at risk individuals possessed a total of 34 retinal lesions, 17 in each group. Two affected individuals and 1 at risk individual had the classical pattern of CHRPE associated with FAPC. The sensitivity of CHRPE as an ocular marker for FAPC in this kindred was 14.2%. Our findings have implications for the use of CHRPE for the presymptomatic screening of family members at risk of FAPC. Therefore, ocular examination should not replace colonoscopic screening in an individual at risk of FAPC.

Radiology and endoscopy in the pretreatment diagnostic management of colorectal cancer

This paper discusses the imaging methods available for the detection and diagnosis of colon cancer, concentrating on endoscopy and barium radiology. Effective utilization of these two methods may be facilitated by using flexible sigmoidoscopy to direct further investigation. There is a need for educational efforts to enhance the performance of endoscopy and barium radiology so that the high standards achieved in some published series are more generally available to patients. New developments in contrast agents will alter rapidly the roles of ultrasound, CT scanning, and magnetic resonance in the investigation and management of colorectal cancer.

Molecular genetic evidence for the delineation of a more severe form of familial adenomatous polyposis which results from fresh mutation

Familial adenomatous polyposis, an inherited pre-malignant condition, is caused by mutation in the adenomatous polyposis coli (APC) gene at chromosome 5q22. The lifetime risk of carcinoma approaches 100%, with an average age at death from cancer of 40 years, allowing most patients to complete reproduction. Since there is no evidence for a rising incidence, this is at variance with an apparently high mutation rate. We present evidence for the delineation of a severe form, which hitherto has largely been maintained by fresh mutation. An atypically high frequency of loss of heterozygosity at chromosome 5q22 in small adenomas correlated with an early age of onset or malignancy in two patients, both due to fresh mutation. In both cases, the mutation in APC was shown to be a commonly occurring deletion, leading us to postulate the co-existence of a modifying gene.

Screening practice for familial adenomatous polyposis: the potential for regional registers

Existing screening practice for familial adenomatous polyposis (FAP) was evaluated in 47 families with FAP notified to the West Midlands Polyposis Register between February 1988 and July 1990. Of these 269 individuals, 107 were known to be affected and 162 were at 50 per cent prior risk of developing FAP; 35 decreased affected individuals from living generations were included in the analysis. Of 105 individuals in the at-risk group aged between 12 and 40 years, only 55 (52 per cent) were under follow-up by bowel examination. Thirty-seven affected individuals had developed colorectal carcinoma before diagnosis; the incidence was three of 51 (6 per cent) in those diagnosed through screening compared with 34 of 53 (64 per cent) in the unscreened group (P < 0.001). A total of 28 individuals (26 per cent of the FAP population) died from advanced colorectal carcinoma; all were from the unscreened population. In 22 (59 per cent) of the cases of colorectal carcinoma and 17 (61 per cent) of the deaths from advanced colorectal cancer there was a positive family history of FAP; these tumours were therefore potentially preventable through screening and prophylactic surgery. Since establishing the register the median age at diagnosis of the affected patients has been reduced from 32 to 23 years (P = 0.0004) and the incidence of colorectal cancer has fallen from 35 to 14 per cent (P < 0.05). It is concluded that by providing more comprehensive case ascertainment a regional register can have a dramatic effect on this largely preventable form of colorectal cancer. Regional registers are recommended as an essential component of screening for this disease.

Role of congenital hypertrophy of the retinal pigment epithelium in the predictive diagnosis of familial adenomatous polyposis

A study was carried out to evaluate congenital hypertrophy of the retinal pigment epithelium (CHRPE) as a disease marker in a defined population with familial adenomatous polyposis (FAP). Indirect ophthalmoscopy was performed on 75 individuals from 25 known families with FAP, of whom 32 were known to be affected and 43 were at a 50 per cent prior risk of developing the disease. A further ten individuals from five families with hereditary non-polyposis colorectal cancer (HNPCC) were also tested. CHRPE was seen in 28 of the 32 affected individuals, 27 of whom met the criteria for a positive examination. Three individuals at risk of FAP also had positive examinations. Five individuals from the families with HNPCC also had CHRPE, although none met the criteria for a positive examination. Of four types of CHRPE analysed, one (small pigmented dots) was found to be more frequent in older family members (P = 0.012), suggesting that this type of lesion may proliferate with age. Compliance with ophthalmic screening was 97 per cent in families with FAP. Using a combined set of diagnostic criteria, CHRPE identified affected individuals with a specificity of at least 94 per cent and a sensitivity of 84 per cent. Results argue for a combined screening programme for FAP of DNA analysis, indirect ophthalmoscopy and bowel examination.

Congenital hypertrophy of retinal pigment epithelium in patients with colonic polyps associated with cancer family syndrome

Congenital hypertrophy of retinal pigment epithelium (CHRPE) has been shown to be a frequent extracolonic manifestation of adenomatous polyposis coli (APC). The presence of CHRPE in patients with adenomatous polyps from families with cancer family syndrome suggests possible involvement of the APC gene locus in syndromes associated with less florid polyp formation than seen in APC. It also emphasises that caution must be exercised in using the presence of CHRPE clinically as a marker for APC in isolated at-risk individuals.

Incidence and significance of congenital hypertrophy of the retinal pigment epithelium (CHRPE) in familial adenomatous polyposis coli (FAPC)

As part of a population based study of familial colorectal cancer 33 affected patients with familial adenomatous polyposis coli (FAPC) and 33 relatives, at 50% risk of inheriting FAPC, from 24 kindreds, were identified and examined. Fourteen of the affected patients had extracolonic manifestations of the FAPC gene. Twenty-five of the 33 affected patients had one or more areas of congenital hypertrophy of the retinal pigment epithelium (CHRPE) and 20 had more than three CHRPEs, all having bilateral lesions. There were significant interfamilial differences in the ocular findings. Because of this interfamilial difference in the predisposition to develop CHRPEs it is important to establish the CHRPE status of individual FAPC families before the results of ophthalmoscopy can be used to predict the carrier status of at risk relatives.

Phenotypic variation in hereditary nonpolyposis colon cancer syndrome. Association with infiltrative fibromatosis (desmoid tumor)

Familial infiltrative fibromatosis (desmoid tumor) is a recognized complication of familial adenomatous polyposis (FAP) but has not been described in families without colonic polyposis. The authors describe a unique family in which a predisposition to infiltrative fibromatosis and nonpolyposis colon cancer was inherited dominantly through four generations. This report expands the range of phenotypic variation described for the hereditary nonpolyposis colon cancer (HNPCC) syndrome and adds to the extracolonic complications that are common with FAP and HNPCC.

Predictive diagnosis of familial adenomatous polyposis with linked DNA markers: population based study

OBJECTIVES

To evaluate the use of polymorphic DNA probes linked to the APC gene in the presymptomatic diagnosis of familial adenomatous polyposis.

DESIGN

Four DNA probes were tested on an unselected population of patients at risk of familial adenomatous polyposis.

SUBJECTS

The first 47 families notified to the West Midlands familial adenomatous polyposis register. Plus five families sent to our hospital as part of the West of Britain DNA consortium.

MAIN OUTCOME MEASURES

The proportion of families and family members in whom DNA testing could be used to adjust the estimate of risk.

RESULTS

Only 17 families on the register (containing 46% (74/162) of the population at risk) had a suitable pedigree structure for DNA analysis. DNA was analysed in 12 of these families plus the five families from the West of Britain consortium. At least one probe was informative in 27 of the 33 subjects born with 50% risk, but the most informative probe (pi 227) was the one with the highest recombination rate (10%). Flanking markers were informative in only four of the 33 subjects.

CONCLUSIONS

These findings confirm the potential for accurate predictive diagnosis of familial adenomatous polyposis with polymorphic DNA probes, but such an approach is currently limited to about one third of affected families. A combined approach to presymptomatic diagnosis, which includes DNA testing and indirect ophthalmoscopy, is advocated.

Management of familial adenomatous polyposis

The management of FAP involves treatment of affected individuals and their families. Such an approach is best coordinated by registrars working in dedicated registries, in close collaboration with nurses, physicians, surgeons, clinical geneticists and others who become involved in the care of these patients. The large bowel of patients with FAP should be removed (totally or subtotally) by the third decade of life. Screening of other areas at risk is recommended to document the natural history of extracolonic manifestations and to allow study of the effects of intervention. Despite these other, sometimes life-threatening manifestations, a near to normal life span is possible in the majority of patients with FAP. The aims of management of the individual and of the family are to ensure that their quality of life is optimal, that support is provided in times of emotional need, that anxiety is minimized and that relatives are adequately screened and treated.

Overview of screening and management of familial adenomatous polyposis

The rarity of familial adenomatous polyposis (FAP) means that many clinicians may be unaware of the major advances that have taken place in screening for the condition over the past five years. This review is not only to document the current scene but also to give details of those involved in establishing registries throughout the country. FAP is a hereditary disorder which carries with it almost a 100% risk of colorectal cancer. The aim of screening is to detect gene carriers before they present with symptoms attributable to colonic polyps. In this way the incidence of colorectal cancer can be greatly reduced. The use of gene probes to identify patients with FAP is in its infancy but in selected pedigrees gene carriers can be identified using a venous blood sample. The recognition that congenital hypertrophy of the retinal pigment epithelium is an extracolonic manifestation of FAP in most pedigrees allows non-invasive ophthalmological screening of relatives at risk. The combination of these new screening methods with an effective regional registry for FAP can increase the number of patients detected by screening rather than by symptoms. This facilitates appropriate prophylactic surgery and reduces mortality related to colorectal cancer.

Linkage analysis in adenomatous polyposis coli: the use of four closely linked DNA probes in 20 UK families

Linkage analysis was carried out on 20 unselected UK families segregating for adenomatous polyposis coli (APC) using four closely linked DNA probes. Significant lod scores were obtained between APC and three markers: pi 227 (D5S37) theta = 0.16; C11p11 (D5S71) theta = 0.10; and YN5.48 (D5S81) theta = 0.00. The fourth, ECB27 (D5S98), gave low lod scores. The APC gene showed linkage with at least one of the probes used in all families, which is in agreement with previous publications. Combined lod scores are now sufficiently high to allow the use of these probes in presymptomatic diagnosis. Despite the fact that 61% of persons at risk were informative for at least one DNA marker, only 15% were informative with flanking probes. One prenatal diagnosis was performed where the initial request had been for sterilisation.

The UK Northern region genetic register for familial adenomatous polyposis coli: use of age of onset, congenital hypertrophy of the retinal pigment epithelium, and DNA markers in risk calculations

A polyposis register has been established in the Northern Region of England. A total of 48 families with 71 living affected subjects has been identified during the first three years of operation, a prevalence of 2.29 x 10(-5). Indirect ophthalmoscopy identifies the majority of gene carriers by showing multiple areas of congenital hypertrophy of the retinal pigment epithelium (CHRPE). The absence of this sign in families limits its value where a relative with CHRPE has not been identified. Combining eye examination with data on age of onset and linked DNA markers is highly effective in carrier exclusion; 38% of 528 first, second, and third degree relatives had their carrier risk reduced to less than 1 in 1000. Even with such assurance many subjects will request continued bowel screening at a reduced frequency. Little interest has been shown in prenatal diagnosis. The principal value of a genetic register with domiciliary nurse visiting is the reduction in early mortality among unrecognised gene carriers.

Role of a regional register for familial adenomatous polyposis: experience in the northern region

Within 36 months of its formation the Northern Region Polyposis Registry had increased the number of identified gene carriers of familial adenomatous polyposis from 56 to 65 in a population of 3.1 million and had achieved a 15-fold increase in the number of at-risk relatives being regularly screened. Review of the surgical records at the outset of the registry revealed that the mean age at diagnosis of those patients detected by screening was 24.7 years, whereas it was 36.6 years for those detected by symptoms. Ten of the 31 in the latter group had colorectal carcinomas whilst only one of those detected by screening had a cancer and a significantly higher proportion had sphincter-saving surgery. A regional registry can provide an effective screening and counselling service to surgeons treating patients with familial adenomatous polyposis. At-risk relatives are best assessed by combining results of the different screening procedures now available but the prime requirement of a successful registry is dedicated domiciliary counselling.

Linked DNA markers for presymptomatic diagnosis of familial adenomatous polyposis

41 symptom-free individuals aged 0-39 years who were at risk of familial adenomatous polyposis (FAP) were genotyped with six linked DNA probes. 28 individuals were informative for probes flanking the gene and 14 people assigned a probe-derived risk of over 0.93 were subsequently shown to be affected by clinical screening. 4 individuals who had been discharged from follow-up were designated high risk by this method. In those screened negative, risk was calculated from genotypic, colonic, and CHRPE findings and 89% of subjects had a risk below 0.003. An integrated risk analysis may have an important place in screening programmes for FAP.

A new deletion polymorphism at D5S71 raises the linkage information on adenomatous polyposis coli: implications for presymptomatic diagnosis

Two independent study-groups, one in Britain and the other in the United States, were the first to report linkage between APC and a TaqI restriction fragment length polymorphism (RFLP) at D5S71 (probe C11p11) on chromosome 5q. They found no recombinants in about 50 informative meioses. The same TaqI RFLP was found to be uninformative for linkage in 15 Dutch polyposis families. The recently reported four base-pair deletion polymorphism (DEL1) at D5S71 has raised the polymorphism information content of this marker from 0.17 to 0.40 in the Dutch population. Seven of 20 polyposis families screened for the DEL1 as well as the TaqI polymorphism gave a combined peak lod score of 5.68 with no recombinants in 37 informative meioses. These data, together with those so far reported in the literature, raise the peak lod score to 17.09 at a recombination fraction of 0.05, the 95% upper confidence limit being 0.09. In combination with the use of another informative marker, D5S81 (probe YN5.48) closely mapping on the other side of APC, the presymptomatic diagnosis of the disease can be made with more than 99.9% certainty. It has to be stressed, however, that the the possible existence of more than one polyposis locus cannot, as yet, be excluded.

Association of congenital hypertrophy of the retinal pigment epithelium with familial adenomatous polyposis

Ophthalmological examinations were performed in 49 people (43 patients) from 24 families affected by familial adenomatous polyposis (FAP). No features of congenital hypertrophy of the retinal pigmented epithelium (CHRPE) were noted in six first-degree relatives without colonic polyps. Patients with Gardner's syndrome exhibited CHRPE more frequently than those without exostosis or desmoid tumour (91 per cent versus 45 per cent). In addition the prevalence of CHRPE was slightly higher in the patients with gastric or duodenal polyps (68 per cent compared with 50 per cent) in those who had a normal gastroduodenal examination. There were 11 families in which two or more patients underwent ophthalmological examinations. In five of these 11 families, all 12 patients were negative for CHRPE. In four of the remaining six families, all 11 patients had CHRPE. CHRPE is one of the pleiotropy of FAP and ophthalmological examination is an important screening test for the family of patients with CHRPE associated with FAP.

Pigmented lesions of the retinal pigment epithelium and familial adenomatous polyposis

Bilateral pigmented fundus lesions were found in 65 out of 72 patients with familial adenomatous polyposis, an additional five patients having unilateral lesions. With a family history of familial adenomatous polyposis, the occurrence of multiple bilateral fundus lesions indicates the presence of the abnormal gene, as does the occurrence of oval pigmented lesions with surrounding pale haloes. The absence of pigmented fundus lesions does not exclude the abnormal genotype, while the presence of occasional pigmented spots can be found in an appreciable percentage of the population. Ocular examination would, however, appear to be valuable in screening those at risk, with a positive yield in most carriers of the gene for familial adenomatous polyposis.