Family-specific Mutation Research Articles

Uptake of Family-Specific Mutation Genetic Testing Among Relatives of Patients with Ovarian Cancer with BRCA1 or BRCA2 Mutation.

PurposeThe BRCA1 or BRCA2 gene is transmitted in an autosomal dominant fashion, and genetic testing of first-degree relatives of patients with family-specific mutation (FSM) is recommended. This study examined factors affecting the uptake of FSM testing among relatives of patients with peritoneal, ovarian, or fallopian tube (POFT) cancer with confirmed BRCA1 or BRCA2 germline mutation.Materials and MethodsData from medical charts of 392 eligible patients and their relatives who had undergone outpatient genetic counseling/testing were retrospectively reviewed. Clinical factors were compared between family members who had and had not undergone genetic counseling/testing.ResultsThe uptake of FSM testing was 30.5% (129/423) among first-degree living relatives and 53.5% (69/129) within the overall family unit. The average time from genetic testing of the proband to the first FSM test within a family was 168 days (range, 23 to 681 days). Having a living father (33.8% vs. 13.3%, p=0.007) and daughter (79.4% vs. 60.3%, p=0.019) increased the uptake of FSM testing. FSM testing was more likely among female than among male relatives of cancer patients (40.9% vs. 17.6%, p < 0.001).ConclusionApproximately one-third of first-degree relatives of patients with a POFT cancer with BRCA1 or BRCA2 mutation underwent FSM testing. Having a living father or daughter was a factor affecting the uptake of FSM testing, which was higher among female than among male relatives of the proband. This discrepancy might be due to a misconception that the BRCA gene is associated with women rather than with men.

Genetic diagnostics of hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease)

Introduction: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant multisystemic vascular disease with a worldwide prevalence of 1:5000 - 1:10000. Diagnosis is based on clinical Curacao criteria. Approximately 85% of HHT cases have heterozygous family-specific mutations in the ENG or ACVRL1 genes. Aim: We investigated 23 Hungarian HHT families, established the genetic diagnosis, executed family-screening and confirmed founder effects. Method: Probands were identified by the stratified population screening of the primary attendance area of our institution and from individuals contacting our study group voluntarily. Diagnosis is based on the otorhinolaryngological physical examination completed with characteristic telangiectasis sites, a visceral arteriovenous malformation screening and the sequence analysis of ENG and ACVRL1 genes. The family screening consists of physical examination and genetic screening for the family-specific mutation, followed by the arteriovenous malformation screening in patients with definite/suspected HHT and/or in individuals with the mutation. Results: Sixty-three individuals with family-specific mutations were identified in 22 families, 48 of them with definite and 12 with suspected HHT. Seven ENG and ACVRL1 mutations were detected, respectively; most of these are pathogenic. Three founder mutations were observed. One proband with definite HHT had wild-type alleles in all tested HHT-specific loci. Conclusions: The significance of genetic testing is confirming or excluding HHT in young asymptomatic individuals in families with pathogenic mutations. As ENG and ACVRL1 mutations result in overlapping fenotypes, the genetic testing lacks any prognostic value. The identification of founder effects might simplify the genetic diagnosis of new HHT patients from a given region. Orv Hetil. 2019; 160(18): 710-719.

The Stratified Population Screening of Hereditary Hemorrhagic Telangiectasia.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant multisystemic vascular disease with a wordwide prevalence of 1:5000-1:10000. We introduce our algorithm for the stratified population screening of HHT. Probands are selected from the consecutive hospital database review for HHT (I7800) and recurrent epistaxis (R0400) and the review of patient records referred by family practicioners. A proportion of probands might be de novo diagnosed with HHT in the 10-year study period. The checkup of probands consists of physical examination, arteriovenous malformation exploration and and genetic testing (ACVRL1 and ENG sequence analysis). The family screening of HHT consists of physical examination and screening for the family-specific mutation of each at-risk individual, and furthermore, arteriovenous malformation exploration in individuals with suspected/definite HHT and/or carrying the mutation. Twenty-five definite HHT patients were explored: 7 of them by the I7800 review, 1 by the R0400 review, 3 were de novo diagnosed, and the remaining 14 were explored by the systematic family screening. Considering the 20 patients alive at the end of the study period and the unavailable 5 potential HHT patients and 12 at-risk family members, the HHT prevalence is estimated to be 1:6090-1:11267 in our study area, implying our algorithm's effectivity in the stratified population screening of HHT.

Familial Hypercholesterolemia: Cascade Screening in Children and Relatives of the Affected.

Familial Hypercholesterolemia (FH) is an inherited disorder of lipid metabolism characterized by very high low density lipoprotein (LDL) cholesterol since birth, resulting in premature atherosclerosis and coronary artery disease (CAD). Cascade screening of children and family members of proven FH individuals can identify more subjects who have high LDL cholesterol or the family mutation and appropriate intervention can reduce their risk of atherosclerosis and prevent its complications. Cascade screening by molecular testing, was carried out in 133 family members, comprising 24 children, of 31 probands with FH having a pathogenic mutation in LDLR/ApoB gene. Lipid profiles were obtained in 44 family members including 11 children. Of 133 family members tested, 88 (66.1%) were identified to carry the family mutation. Twelve of these were children below 18 y of age and 76 were adults. CAD was present in 15 (11.2%) family members and 63(47.4%) family members, including nine children, were already on Lipid Lowering Therapy. Cascade screening led to identification of 88 new cases, with a pathogenic mutation, who were at a very high risk of developing premature CAD. The authors identified 12 children with family specific mutation, out of which 9 were initiated on low dose statin therapy. Four homozygous children were treated with high dose statins because of substantially increased risk of CAD. Cascade screening, therefore, proved to be a successful initiative towards primary prevention of CAD in India.

No evidence of increased breast cancer risk for proven noncarriers from BRCA1 and BRCA2 families.

In families screened for mutations in the BRCA1 or BRCA2 genes and found to have a segregating mutation the breast cancer risk for women shown not to carry the family-specific mutation might be at above "average" risk. We assessed the risk of breast cancer in a clinic based cohort of 725 female proven noncarriers in 239 BRCA1 and BRCA2 families compared with birth-matched controls from the Danish Civil Registration System. Prospective analysis showed no significantly increased risk for breast cancer in noncarriers with a hazard ratio of 0.67 [95% confidence interval (CI) 0.32-1.42, p=0.29] for all family members who tested negative and 0.87 (95% CI 0.38-1.97, p=0.73) for non-carries who were first-degree relatives of mutation carriers. Proven noncarriers from BRCA1 and BRCA2 families have no markedly increased risk for breast cancer compared to the general population, and our data do not suggest targeted breast cancer surveillance for noncarriers from BRCA1 and BRCA2 families.

Gene panel testing for hereditary breast cancer.

Inherited predisposition to breast cancer is explained only in part by mutations in the BRCA1 and BRCA2 genes. Most families with an apparent familial clustering of breast cancer who are investigated through Australia's network of genetic services and familial cancer centres do not have mutations in either of these genes. More recently, additional breast cancer predisposition genes, such as PALB2, have been identified. New genetic technology allows a panel of multiple genes to be tested for mutations in a single test. This enables more women and their families to have risk assessment and risk management, in a preventive approach to predictable breast cancer. Predictive testing for a known family-specific mutation in a breast cancer predisposition gene provides personalised risk assessment and evidence-based risk management. Breast cancer predisposition gene panel tests have a greater diagnostic yield than conventional testing of only the BRCA1 and BRCA2 genes. The clinical validity and utility of some of the putative breast cancer predisposition genes is not yet clear. Ethical issues warrant consideration, as multiple gene panel testing has the potential to identify secondary findings not originally sought by the test requested. Multiple gene panel tests may provide an affordable and effective way to investigate the heritability of breast cancer.

Prevalence of PALB2 mutations in Australasian multiple-case breast cancer families

IntroductionPopulation-based studies of breast cancer have estimated that some PALB2 mutations confer a breast cancer risk (penetrance) comparable to the average pathogenic mutation in BRCA2. As this risk is of clinical relevance, we sought to identify mono-allelic PALB2 mutations and determine their frequencies in multiple-case breast cancer families attending Familial Cancer Clinics in Australia and New Zealand.MethodsThe youngest affected woman, not known to carry a mutation in BRCA1 or BRCA2, from 747 multiple-case breast cancer families participating in kConFab were selected for PALB2 mutation screening. The coding and flanking intronic regions of PALB2 in DNA extracted from blood were screened using high-resolution melt curve analysis with Sanger sequencing confirmation. Where possible, relatives of women found to carry PALB2 mutations were genotyped for the family-specific mutation, mutant transcripts were characterised and breast tumours arising in mutation carriers were recalled and reviewed. Missense mutations were assessed for potential to disrupt protein function via SIFT, Align GVGD and Polyphen-2.ResultsThe mutation screen identified two nonsense mutations (PALB2 c.3113G>A in eight women and PALB2 c.196C>T in one woman), two frameshift mutations (PALB2 c.1947_1948insA and PALB2 c.2982_2983insT each in one woman), 10 missense variants, eight synonymous variants and four variants in intronic regions. Of the four PALB2 mutations identified that were predicted to produce truncated protein products, only PALB2 c.1947_1948insA had not previously been reported. PALB2 c.3113G>A and PALB2 c.196C>T were previously identified in the Australian population whereas PALB2 c.2982_2983insT was previously reported in the UK population. Transcripts derived from three of these mutant PALB2 alleles were vulnerable to nonsense-mediated decay. One missense mutation (PALB2 c.2993G>A) was predicted to disrupt protein function via the three in silico assessment methods applied. The majority of breast cancers arising in carriers that were available for review were high-grade invasive ductal carcinomas. Conclusions: About 1.5% (95% CI 0.6to 2.4) of Australasian multiple-case breast cancer families attending clinics are segregating protein-truncating mutations in PALB2, most being PALB2 c.3113G>A, p.Trp1038*. Given the prevalence, breast cancer risk, and tumour grade associated with this mutation, consideration of clinical PALB2 testing is warranted.

When is it best to test? Attitudes of health professionals regarding genetic testing for Familial Adenomatous Polyposis (FAP)

Familial Adenomatous Polyposis (FAP) is a well described autosomal dominant syndrome, whereby individuals develop multiple (up to thousands) of adenomatous polyps in the large bowel, conferring an extremely high risk of bowel cancer if left untreated. If the family specific mutation is known, genetic testing can be offered to at risk individuals to determine the need for endoscopic surveillance. Guidelines suggest starting endoscopic surveillance from the early teens. Most individuals with FAP undergo colectomy between the ages of 15 and 25 years [1]. Recent studies have shown that many adults with FAP want their children to undergo genetic testing before the age of 12 years, the approximate age at which genetic testing is usually offered in Australia [2,3]. Health professionals working in cancer genetics in Australia and New Zealand completed a web based survey aimed at examining their attitudes and experiences regarding genetic testing for young people at risk of FAP. Findings from the survey provide an insight into the views and practices of health professionals working in this area, including: the age at which they believe testing young people is most appropriate; their experiences regarding parental requests for testing of younger children; and whether the option of prenatal testing and pre-implantation genetic diagnosis is routinely discussed with individuals who have FAP and are also of child bearing age. These have important implications for clinical practice within the Australian cancer genetics community.

Prospective study of breast cancer risk for mutation negative women from BRCA1 or BRCA2 mutation positive families

Published studies have reached contradictory conclusions regarding breast cancer risk for women from families segregating a BRCA1 or BRCA2 mutation who do not carry the family-specific mutation. Accurate estimation of breast cancer risk is crucial for appropriate counselling regarding risk management. The aim of this study is to prospectively assess whether breast cancer risk for mutation negative women from families segregating BRCA1 or BRCA2 mutations is greater than for women in the general population. Eligible women were 722 first-, second- and third-degree relatives of a BRCA1 or BRCA2 mutation carrier from 224 mutation positive (128 BRCA1, 96 BRCA2) families, had no personal cancer history at baseline, and had been tested and found not to carry the family-specific mutation. Self-reported family history of cancer, preventive interventions and verified cancer diagnoses were collected at baseline, and every 3 years thereafter. Median follow-up was 6.1 years (range 0.1-12.4 years). Time at risk of breast cancer was censored at cancer diagnosis or risk-reducing surgery. Standardised incidence ratios (SIR) were estimated by comparing observed to population incidences of invasive breast cancer using Australian Cancer Incidence and Mortality Books. Six cases of invasive breast cancer were observed. The estimated SIRs were 1.14 (95% CI: 0.51-2.53) overall (n = 722), 1.29 (95% CI: 0.58-2.88) when restricted to first- and second-degree relatives of an affected mutation carrier (n = 442) and 0.48 (95% CI: 0.12-1.93) when restricted to those with no family history of breast cancer in the non-mutation carrying parental lineage (n = 424). There was no evidence that mutation negative women from families segregating BRCA1 or BRCA2 mutations are at increased risk of breast cancer. Despite this being the largest prospective cohort to assess this issue, moderately increased breast cancer risk (2-fold) cannot be ruled out.

Hereditary hemorrhagic telangiectasia: two distinct ENG deletions in one family

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by aberrant vascular development. Mutations in endoglin (ENG) or activin A receptor type II-like 1 (ACVRL1) account for around 90% of HHT patients, 10% of those are large deletions or duplications. We report here the first observation of two distinct, large ENG deletions segregating in one pedigree. An ENG exon 4-7 deletion was observed in a patient with HHT. This deletion was identified in several affected family members. However, some affected family members had an ENG exon 3 deletion instead. These deletions were detected by multiplex ligation-dependent probe amplification and confirmed by mRNA sequencing and an oligo-CGH array. Linkage analysis revealed that one individual with the exon 3 deletion inherited the same chromosome from his mother who has the exon 4-7 deletion. This finding has important clinical implications because it shows that targeted family-specific mutation analysis for exon deletions could have led to the misdiagnosis of some affected family members.

Determinants of factor VIII plasma levels in carriers of haemophilia A and in control women

Factor VIII (FVIII) levels show a considerable variability in female carriers of haemophilia A. Presently, the reasons for this are poorly understood. The aim of the study was to elucidate the influence of genetic and non-genetic parameters on FVIII plasma levels in carriers (n = 42). Results were compared with age-matched healthy women without carriership of haemophilia A (n = 42). Each carrier was tested for the family-specific mutation, ABO blood group, FVIII level, von Willebrand factor (VWF) antigen and activity and C-reactive protein (CRP). FVIII levels were lower in carriers compared to non-carriers [74% (51-103) vs. 142% (109-169), P < 0.001]. No statistically significant differences were observed between the two groups with respect to VWF activity, prothrombin-time, hs-CRP, fibrinogen, body mass index (BMI), age and smoking status as well as the distribution of ABO blood groups. In non-carriers, FVIII was statistically significantly correlated with BMI, activated partial thromboplastin time (APTT), VWF antigen, hs-CRP and fibrinogen. In carriers, significant correlations between FVIII and APTT, VWF antigen and activity were found, whereas BMI, hs-CRP or fibrinogen did not correlate with FVIII. In non-carriers, the association of FVIII with ABO blood groups was statistically significant (P = 0.006), but not in carriers of haemophilia A (P = 0.234). The type of FVIII gene mutation did not influence FVIII levels. Carrier status is the major determinant of a carrier;s FVIII plasma level. Factors known to influence FVIII levels in the general population do not significantly affect FVIII activity in carriers, neither does the type of mutation influence FVIII levels.

Malignant hyperthermia susceptibility diagnosed with a family-specific ryanodine receptor gene type 1 mutation

Malignant hyperthermia (MH) is an autosomal dominant disorder of skeletal muscle calcium regulation, and the rate of calcium-induced calcium release (CICR), determined by using skinned fibers of skeletal muscle, has been employed as a diagnostic test for MH susceptibility in Japan. The ryanodine receptor (RYR1), encoding the major calcium-release channel in skeletal muscle sarcoplasmic reticulum, has been shown to be mutated in a number of MH pedigrees. We experienced the detection of accelerated CICR and/or an RYR1 mutation in a patient with an MH episode and his family. Accelerated CICR and an RYR1 mutation (c.14512C>G, p.L4838V) were found in the patient and his father. The MH-causative mutation (c.14512C>G, p.L4838V) was also found in his brother and his son (resulting in the diagnosis of MH without the CICR test), but the mutation was not found in his mother or two daughters. With the detection of the family-specific mutation in other family members, the diagnosis of MH was made without the invasive CICR test.

Predictors of psychological distress among individuals with a strong family history of malignant melanoma

Despite rapid advancements in molecular genetics research, little is known about the psychological experiences of individuals with a family history of melanoma. The present study aimed to identify factors contributing to psychological distress among affected and unaffected individuals with a strong family history of melanoma. A total of 121 adults who had recently been informed of the identification of a family-specific mutation in the CDKN2A melanoma susceptibility gene, completed a self-report questionnaire assessing cancer-specific and generalized distress, and a variety of potential predictors. Having a personal history of melanoma (OR = 3.37, p = 0.033), perceiving greater family implications of melanoma (OR = 2.52, p < 0.0001), and the tendency to monitor for threatening information (OR = 3.12, p = 0.008) were associated with melanoma-specific distress. Being childless (beta = 2.09, p = 0.007), perceiving sun exposure as an important cause of melanoma (beta = 1.15, p = 0.015), and perceiving greater family implications of melanoma (beta = 1.02, p = 0.002) were associated with greater generalized anxiety, while monitoring moderated the relationship between endorsement of a genetic model of melanoma and generalized anxiety (p = 0.005). As in other common familial cancers, distress was relatively uncommon in this familial melanoma cohort, even after notification of the presence of a family mutation. Participants do not contemplate their melanoma risk in isolation, but evaluate their risk vis-à-vis the experiences of their relatives.

Cancer Risk Management Practices of Noncarriers WithinBRCA1/2Mutation–Positive Families in the Kathleen Cuningham Foundation Consortium for Research Into Familial Breast Cancer

Women from BRCA mutation-positive families who do not carry the family-specific mutation are generally at average cancer risk and therefore do not require intensive risk management. Participants were female noncarriers from BRCA mutation-positive families who had responded to 3 yearly follow-up questionnaires and had chosen to either receive or not receive their genetic test result. In the former group, undertaking mammography younger than age 40 years or more than once every 2 years, clinical breast examination (CBE) more than yearly, breast self-examination (BSE) more than monthly, or any transvaginal ultrasound (TVU) or CA-125 was considered overscreening. Screening behaviors of women who did and did not know their genetic test result were compared. Logistic regression and nonparametric analyses were performed to identify demographic and psychosocial factors (respectively) associated with overscreening. Of 325 eligible women, 116 knew their mutation status and 209 did not. For the first group, proportions overscreening were mammography, 53%; CBE, 10%; BSE, 11%; TVU, 7%; and CA-125, 10%. There were no significant differences in screening behaviors between the groups. In those aware of their mutation status, parous women were more likely to overuse mammography (odds ratio [OR] = 4.4; 95% CI, 1.1 to 17; P = .03) and women with one or more first-degree relative with ovarian cancer (OC) were more likely to overuse OC screening (TVU: OR = 6.00; 95% CI, 1.0 to 35.1; P = .047, and CA-125: OR = 6.50; 95% CI, 1.49 to 28.4; P = .013). The reasons for overuse of screening (particularly mammography) by mutation noncarriers require additional elucidation given the potential for harm.

Loss of heterozygosity at the BRCA2 locus is a common finding in prostate cancer in men with a germline BRCA2 mutation

10539 Background: The prevalence of prostate cancer (PC) is higher in men with a germline mutation in BRCA2 and to a lesser extent BRCA1. It is unclear as to whether a causal relationship exists between these mutations and PC tumorigenesis. The primary aim of this pilot study was to examine for loss of heterozygosity (LOH) in PC samples from men with a known BRCA1/2 mutation. Secondary aims included assessment of the clinical and pathological features of PC in these individuals. Methods: Subjects were male carriers of a germline BRCA1/2 mutation enrolled in kConFab with a diagnosis of PC. LOH analysis was performed using multiplex ligation-dependent probe amplification and confirmed using PCR and sequencing. Clinical data was obtained on all individuals together with histopathology review. Results: In total, 134 pedigrees from BRCA1/2 mutation positive families known to include = 1men with PC were reviewed; 192 men were identified as having PC, however, only 26 were found to carry a pathogenic family specific mutation. Of these, 14 were ineligible as prostate tissue was unavailable. LOH was therefore assessed in 12 subjects (3 BRCA1 and 9 BRCA2). LOH at the BRCA2 locus was seen in 8/9 (89%) subjects with a BRCA2 mutation whilst the ninth showed no LOH. None of the samples from BRCA1 carriers were found to have LOH at the BRCA1 locus. For samples showing LOH, sequencing confirmed loss of the wild-type allele. No unique clinical or histopathological subtype was identified. Conclusions: LOH appears to occur very frequently at the BRCA2 locus in PC arising in men known to carry a germline BRCA2 mutation with LOH heavily biased towards loss of the wild-type allele. Whilst the cohort studied is small, these two results strongly indicate that BRCA2 is a tumour suppressor of PC and is the first gene shown to have this property. In contrast, failure to identify LOH in the BRCA1 samples suggests that BRCA1 is unlikely to be integral in the development of PC. These results should be confirmed in a larger cohort and further research into the mechanisms of BRCA2 induced prostate tumorigenesis is warranted. No significant financial relationships to disclose.

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.

Mutation testing in Treacher Collins Syndrome.

To report on a study where 97 subjects were screened for mutations in the Treacher Collins syndrome (TCS) gene TCOF1. Ninety-seven subjects with a clinical diagnosis of TCS were screened for potential mutations in TCOF1, by means of single strand conformation polymorphism (SSCP) analysis. In those subjects where potential mutations were detected, sequence analysis was performed to determine the site and type of mutation present. Thirty-six TCS-specific mutations are reported including 27 deletions, six point mutations, two splice junction mutations, and one insertion/deletion. This brings the total number of mutations reported to date to 105. The importance of detection of these mutations is mainly in postnatal diagnosis and genetic counselling. Knowledge of the family specific mutation may also be used in prenatal diagnosis to confirm whether the foetus is affected or not, and give the parents the choice of whether to continue with the pregnancy.

Hypertrophic Cardiomyopathy

ypertrophic cardiomyopathy (HCM) is a fascinatingdisease that has intrigued and challenged cardiolo-gists for decades. Initially a diagnosis made bymaster clinicians adept at translating bedside dynamic aus-cultation into hemodynamic pathophysiology, HCM contin-ues to challenge the frontiers of diagnosis and technology.The development of 2D and Doppler echocardiography pro-vided the greatest increment in understanding the complexityof HCM. While clinicians at large became skilled at thebedside detection of dynamic left ventricular outflow obstruc-tion, echocardiography revealed that many more patients hadunexplained left ventricular hypertrophy (LVH) consistentwith HCM but without evidence of obstruction. In fact, thenonobstructive, “silent” forms are more frequent than theobstructive, “noisy” variants. The pattern and severity ofLVH are now appreciated as heterogeneous and diastolicdysfunction as highly prevalent.

Genotype-phenotype correlations in families with deletions in the von Hippel-Lindau (VHL) gene.

Von Hippel-Lindau (VHL) disease is a hereditary tumor syndrome characterized by predisposition for bilateral and multi-centric hemangioblastoma in the retina and central nervous system, pheochromocytoma, renal cell carcinoma, and cysts in the kidney, pancreas, and epididymis. We describe five families for which direct sequencing of the coding region of the VHL gene had failed to identify the family-specific mutation. Further molecular analysis revealed deletions involving the VHL gene in each of these families. In four families, partial deletions of one or more exons were detected by Southern blot analysis. In the fifth family, FISH analysis demonstrated the deletion of the entire VHL gene. Our results show that (quantitative) Southern blot analysis is a sensitive method for detecting germline deletions of the VHL gene and should be implemented in routine DNA diagnosis for VHL disease. Our data support the previously established observation that families with a germline deletion have a low risk for pheochromocytoma. Further unraveling of genotype-phenotype correlations in VHL disease has revealed that families with a full or partial deletion of the VHL gene exhibit a phenotype with a preponderance of central nervous system hemangioblastoma.

Value of predictive genetic testing in management of hereditary non-polyposis colorectal cancer (HNPCC)

To investigate the impact of predictive genetic testing on colonoscopic surveillance in an extended family with hereditary non-polyposis colorectal cancer (HNPCC). Familial Bowel Cancer Service, The Royal Melbourne Hospital, Victoria. 96 people registered with the Service who were apparently unaffected members of an extended family that met the classic Amsterdam criteria for HNPCC and carried an MLH1 gene mutation (IVS9 + 3insT). Predictive genetic testing was offered in a cascade manner to at-risk family members; mutation-positive individuals were advised to have annual colonoscopic surveillance, while mutation-negative individuals were withdrawn from surveillance. Previous compliance with recommended colonoscopic surveillance; uptake and results of genetic testing; expected effect of genetic test results on number of colonoscopies over five years. 22 of the 96 family members (23%) were not complying with recommended surveillance. Of 48 individuals offered predictive genetic testing, 41 (85%) responded and 39 (81%) underwent testing. Seven of the 39 (18%) were positive for the family-specific mutation, and 32 (82%) were negative. The 39 tested individuals and 37 of their descendants who were registered with the screening program had undergone 70 colonoscopies in the five years before genetic testing. In the five years after testing, only 37 surveillance colonoscopies were planned (annual or two-yearly colonoscopies for the six mutation-positive individuals and five-yearly colonoscopies for four mutation-negative individuals with previously identified adenoma), an almost 50% reduction in colonoscopies. Predictive genetic testing in HNPCC families allows many individuals to be withdrawn from regular colonoscopic surveillance. It may therefore reduce costs, as well as have emotional benefits for many individuals.