Analysis of rare disruptive germline mutations in 2,135 enriched BRCA-negative breast cancers excludes additional high-impact susceptibility genes

BACKGROUND

Breast cancer has a significant heritable basis, of which approximately 60% remains unexplained. Testing for BRCA1/BRCA2 offers useful discrimination of breast cancer risk within families, and identification of additional breast cancer susceptibility genes could offer clinical utility.

PATIENTS AND METHODS

We included 2,135 invasive breast cancer cases recruited via the BOCS study, a retrospective UK study of familial breast cancer.

ELIGIBILITY CRITERIA

female, BRCA-negative, white European ethnicity, and one of: i) breast cancer family history, ii) bilateral disease, iii) young age of onset (<30 years), iv) concomitant ovarian cancer. We undertook exome sequencing of cases and performed gene-level burden testing of rare damaging variants against those from 51,377 ethnicity-matched population controls from gnomAD.

RESULTS

159/2135 (7.4%) cases had a qualifying variant in an established breast cancer susceptibility gene, with minimal evidence of signal in other cancer susceptibility genes. Known breast cancer susceptibility genes PALB2, CHEK2 and ATM were the only genes to retain statistical significance after correcting for multiple testing. Due to the enrichment of hereditary cases in the series, we had good power (>80%) to detect a gene of BRCA1-like risk (odds ratio = 10.6) down to a population minor allele frequency of 4.6 x 10^-5 (1 in 10,799, less than one tenth that of BRCA1)and of PALB2-like risk (odds ratio = 5.0) down to a population minor allele frequency of 2.8 x 10^-4 (1 in 1,779, less than half that of PALB2). Power was lower for identification of novel moderate penetrance genes (odds ratio = 2-3) like CHEK2 and ATM.

CONCLUSIONS

This is the largest case-control whole-exome analysis of enriched breast cancer published to date. Whilst additional breast cancer susceptibility genes likely exist, those of high penetrance are likely to be of very low mutational frequency. Contention exists regarding the clinical utility of such genes.

Visual perspective as a two-dimensional construct in episodic future thought

Visual perspective (first-person vs. third-person) is a salient characteristic of memory and mental imagery with important cognitive and behavioural consequences. Most work on visual perspective treats it as a unidimensional construct. However, third-person perspective can have opposite effects on emotion and motivation, sometimes intensifying these and other times acting as a distancing mechanism, as in PTSD. For this reason among others, we propose that visual perspective in memory and mental imagery is best understood as varying along two dimensions: first, the degree to which first-person perspective predominates in the episodic imagery, and second, the degree to which the self is visually salient from a third-person perspective. We show that, in episodic future thinking, these are anticorrelated but non-redundant. These results further our basic understanding of the potent but divergent effects visual perspective has on emotion and motivation, both in everyday life and in psychiatric conditions.

Virtual arthroplasty follow-up: five-year data from a district general hospital

INTRODUCTION

Follow-up after hip and knee arthroplasty is advocated to identify asymptomatic loosening and improve patient satisfaction. There are, however, financial and time implications associated with regular clinic appointments. Assessment through virtual means has been suggested as an alternative.

MATERIALS AND METHODS

At the West Suffolk Hospital, following arthroplasty surgery of the lower limb, patients are followed-up via a questionnaire at one and five years postoperatively, then subsequently at five-yearly intervals. Patients are recalled based on the outcome of these assessments. Using a locally compiled data base we identified all patients reviewed between 2011 and 2015 using this virtual assessment process and examined their outcomes.

RESULTS

During the five years of follow-up, 5,380 patients were eligible for assessment. Compliance varied from 77% follow up for hips and 83% for knees. Ten patients were recalled following total hip replacement, eight for x-ray changes and one for a poor satisfaction score. Five went on to undergo revision surgery. Some 56 recalls to clinic following knee arthroplasty were seen; 42 due to a poor Oxford Knee Score, 6 with associated x-ray abnormalities and 6 isolated abnormal x-rays. Five subsequently underwent revision surgery; 30 (54%) were discharged after initial review and 18 (32%) were referred to different subspecialties.As a result of the virtual review process, 4,219 clinic appointments were avoided, with no documented admissions as a result of a missed complication from virtual review.

DISCUSSION

A virtual arthroplasty clinic significantly reduces the number of patients attending regular follow-up clinics, without compromising safe practice.

Moving into the mainstream: healthcare professionals' views of implementing treatment focussed genetic testing in breast cancer care

A proportion of breast cancers are attributable to BRCA1 or BRCA2 mutations. Technological advances has meant that mutation testing in newly diagnosed cancer patients can be used to inform treatment plans. Although oncologists increasingly deliver treatment-focused genetic testing (TFGT) as part of mainstream ovarian cancer care, we know little about non-genetics specialists' views about offering genetic testing to newly diagnosed breast cancer patients. This study sought to determine genetics and non-genetics specialists' views of a proposal to mainstream BRCA1 and 2 testing in newly diagnosed breast cancer patients. Qualitative interview study. Nineteen healthcare professionals currently responsible for offering TFGT in a standard (triage + referral) pathway (breast surgeons + clinical genetics team) and oncologists preparing to offer TFGT to breast cancer patients in a mainstreamed pathway participated in in-depth interviews. Genetics and non-genetics professionals' perceptions of mainstreaming are influenced by their views of: their clinical roles and responsibilities, the impact of TFGT on their workload and the patient pathway and the perceived relevance of genetic testing for patient care in the short-term. Perceived barriers to mainstreaming may be overcome by: more effective communication between specialities, clearer guidelines/patient pathways and the recruitment of mainstreaming champions.

Routine germline BRCA1 and BRCA2 testing in patients with ovarian carcinoma: analysis of the Scottish real-life experience

OBJECTIVE

To determine the rates of germline BRCA1 and BRCA2 mutations in Scottish patients with ovarian cancer, before and after a change in testing policy.

DESIGN

Retrospective cohort study.

SETTING

Four cancer/genetics centres in Scotland.

POPULATION

Patients with ovarian cancer undergoing germline BRCA1 and BRCA2 (gBRCA1/2) sequencing before 2013 (under the 'old criteria', with selection based solely on family history), after 2013 (under the 'new criteria', with sequencing offered to newly presenting patients with non-mucinous ovarian cancer), and in the 'prevalent population' (who presented before 2013, but were not eligible for sequencing under the old criteria but were sequenced under the new criteria).

METHODS

Clinicopathological and sequence data were collected before and for 18 months after this change in selection criteria.

MAIN OUTCOME MEASURES

Frequency of germline BRCA1, BRCA2, RAD51C, and RAD51D mutations.

RESULTS

Of 599 patients sequenced, 205, 236, and 158 were in the 'old criteria', 'new criteria', and 'prevalent' populations, respectively. The frequency of gBRCA1/2 mutations was 30.7, 13.1, and 12.7%, respectively. The annual rate of gBRCA1/2 mutation detection was 4.2 before and 20.7 after the policy change. A total of 48% (15/31) 'new criteria' patients with gBRCA1/2 mutations had a Manchester score of <15 and would not have been offered sequencing based on family history criteria. In addition, 20 patients with gBRCA1/2 were identified in the prevalent population. The prevalence of gBRCA1/2 mutations in patients aged >70 years was 8.2%.

CONCLUSIONS

Sequencing all patients with non-mucinous ovarian cancer gives a much higher annual gBRCA1/2 mutation detection rate, with the frequency of positive tests still exceeding the 10% threshold upon which many family history-based models operate.

TWEETABLE ABSTRACT

BRCA sequencing all non-mucinous cancer patients increases mutation detection five fold.

Fetal Dysmorphology-Still an Essential Art. Analysis of the Limitations of Microarray in a Fetal Population and a Look Toward the Genome Sequencing Era

Cytogenomic microarray allows assessment of the genome at higher resolutions than traditional karyotyping. The objective of this study is to evaluate the utility of microarray in a routine fetal autopsy setting before the advent of routine fetal exome/genome sequencing and the issues these technologies may generate. A systematic review of fetal postmortems at 12-24 weeks gestation between January 2011 and December 2014 was undertaken. Cases where there was no consent for audit, research, or genetic testing were excluded as were cases referred to the Procurator Fiscal, stillbirths, and neonatal deaths. Copy number variations were detected in 16 cases. In addition, there was 1 case of uniparental disomy; not all of these were related to the phenotype. There were a number of cases with phenotypic abnormalities and normal array results. Five of these underwent directed mutation analysis-3 were positive. Genetic laboratory investigations such as microarray and Quantitative Fluorescent-Polymerase Chain Reaction may increase the diagnostic yield in the assessment of fetal dysmorphology. However, this study shows that genetic results not only require careful review given the potential uncertain significance but also require phenotypic assessment of the fetus by a competent fetal dysmorphologist to determine the likely causative effect of any detected anomaly. This best practice will also extend to next generation sequencing and interpretation of variants of unknown significance. Fetal medicine teams should ideally include specialists well versed in assessment of fetal anomaly to provide families with the best possible information about the cause of their pregnancy loss and their options for future pregnancies.

Assessing clarity and erasability of commercially available pens for surgical site marking: a comparative study in human volunteers

Background

Marking the surgical site is a well-established part of pre-operative protocol and errors in marking have been implicated in wrong site surgery incidents and are a significant patient safety issue. There are many commercially available marker pens and anecdotally very little consistency in which pen is used or the clarity of marking. Previous studies have shown subjective differences between different pens and the current paper sought to support this evidence with objective data and widen the investigation of commercially available pens.

Methods

Eight marker pens were used to mark two separate sites on three caucasian volunteers. These marks were photographed and assessed by six observers before and after the application of chlorhexidine skin preparation. The observers were blinded to which pen was used for each mark, and rated the clarity of the marks subjectively. The photographs were assessed using image analysis software to give an objective measure of clarity against the skin.

Results

There was a wide variation between the clarity of marks made by the different pens, and also a wide variation in the resistance to skin preparation. The Pentel N50 pen was the outstanding best performing pen across all categories.

Conclusions

It is recommended that the Pentel N50 black marker pen be used for surgical site marking to improve patient safety and avoid adverse events.

Insights from next generation sequencing of the cancer genome

This detailed review provides a history and update of the complex field of cancer genetics. Using examples of progress such as the development of imatinib for chronic myeloid leukemia (which stemmed from the recognition of the Philadelphia chromosome in the 1960s), Michael Stratton, Director of the Sanger Institute in Cambridge is confident that we are now entering the end game of cancer genome sequencing. This has led to other drug therapies, based on knowledge of the molecular changes in some cancers, lung and breast cancers for example.

The use of in utero MRI to supplement ultrasound in the foetus at high risk of developmental brain or spine abnormality

OBJECTIVES

It is widely accepted that the diagnosis of foetal central nervous system (CNS) abnormalities can be improved by performing MRI examinations in utero. Most of the published literature has concentrated on pregnancies in which a developmental abnormality has been detected (or suspected) on ultrasound in an otherwise low-risk pregnancy. In this paper, we test the hypothesis that in utero MRI of the foetal brain in high-risk pregnancies will detect abnormalities not shown by ultrasound at a rate that justifies its use in clinical practice.

METHODS

100 females were recruited into the study from foeto-maternal or clinical genetic departments. They all had a foetus/child with a CNS malformation from an earlier pregnancy, which led to an increased risk of recurrence being quoted for the present pregnancy. All in utero MRI examinations were performed on 1.5 T clinical MRI systems at 18 weeks gestational age or later.

RESULTS

In 78% of cases, the ultrasound and MRI results agreed and showed no abnormality. In 13%, ultrasound and MRI described identical abnormal findings. In 9%, the ultrasound and MRI examinations had discrepant findings; in all these cases the MRI findings described more serious CNS pathology. The effects on management were judged to be major, by at least one assessor, in 7/9 of those cases.

CONCLUSION

As in many other situations involving antenatal detection of CNS abnormalities, in utero MRI should be considered in females with increased risk of foetal CNS malformation based on the results of an earlier pregnancy. Advances in knowledge In utero MRI of the foetus has an important role in antenatal diagnosis of females carrying a foetus with an increased risk of a brain abnormality.

Impaction grafting of the acetabulum with a mixture of frozen, ground irradiated bone graft and porous synthetic bone substitute (Apapore 60)

The clinical and radiological results of 50 consecutive acetabular reconstructions in 48 patients using impaction grafting have been retrospectively reviewed. A 1:1 mixture of frozen, ground irradiated bone graft and Apapore 60, a synthetic bone graft substitute, was used in all cases. There were 13 complex primary and 37 revision procedures with a mean follow-up of five years (3.4 to 7.6). The clinical survival rate was 100%, with improvements in the mean Harris Hip Scores for pain and function. Radiologically, 30 acetabular grafts showed evidence of incorporation, ten had radiolucent lines and two acetabular components migrated initially before stabilising.

Acetabular reconstruction in both primary and revision surgery using a 1:1 mixture of frozen, ground, irriadiated bone and Apapore 60 appears to be a reliable method of managing acetabular defects. Longer follow-up will be required to establish whether this technique is as effective as using fresh-frozen allograft.

The Birmingham Hip Resurfacing: 5-year clinical and radiographic results from a District General Hospital

We prospectively examined the functional and radiographic outcomes of a serial cohort of 104 Birmingham Hip Resurfacings in an independent centre. Final follow-up was to a mean of 61 months, and six cases were lost to follow-up. Excellent results were obtained in 91%, but obese patients had significantly (p < 0.03) poorer post-operative outcomes. Whilst there were no cases of neck fracture neck narrowing of up to 20 mm was noted. Radiolucent lines were present in a single zone in 9.4% (9/96) acetabular and 3.1% (3/96) femoral components. However, no components were definitely loose and there were no revisions for any reason during the period of the study. This independent series confirms that the Birmingham Hip Resurfacing gives excellent early clinical results and little early evidence of radiographic failure. The high rate of neck narrowing gives us cause for concern and we would recommend regular radiographic follow-up.

Prospective surveillance of women with a family history of breast cancer: auditing the risk threshold

To evaluate current guidelines criteria for inclusion of women in special ‘breast cancer family history’ surveillance programmes, records were reviewed of women referred to Scottish breast cancer family clinics between January 1994 and December 2003 but discharged as at ‘less than ‘moderate’ familial risk’. The Scottish Cancer Registry was then interrogated to determine subsequent age-specific incidence of breast cancer in this cohort and corresponding Scottish population figures. Among 2074 women, with an average follow-up of 4.0 years, 28 invasive breast cancers were recorded up to December 2003, where 14.4 were expected, a relative risk (RR) of 1.94. Eleven further breast cancers were recorded between January 2004 and February 2006 (ascertainment incomplete for this period). The overall RR for women in the study cohort exceeded the accepted ‘cutoff’ level (RR=1.7) for provision of special counselling and surveillance. The highest RR was found for the age group 45–59 years and this group also generated the majority of breast cancers. The National Institute for Clinical Excellence (‘NICE’) guidelines appear to be more accurate than those of the Scottish Intercollegiate Guidelines Network (‘SIGN’) in defining ‘moderate’ familial risk, and longer follow-up of this cohort could generate an evidence base for further modification of familial breast cancer services.

Spinocerebellar ataxia type 8 in Scotland: frequency, neurological, neuropsychological and neuropsychiatric findings

OBJECTIVES

The objectives of this study were to: (i) establish whether the spinocerebellar ataxia type 8 (SCA 8) expansion is associated with ataxia in Scotland; (ii) test the hypothesis that SCA 8 is associated with neuropsychological impairment; and (iii) review neuroradiological findings in SCA 8.

METHODS

The methods included: (i) measurement of SCA 8 expansion frequencies in ataxic patients and healthy controls; (ii) comprehensive neuropsychological assessment of patients with SCA 8 and matched controls, neuropsychiatric interview; and (iii) comparison of patient and matched control magnetic resonance imaging (MRI) scans.

RESULTS

(i) 10/694 (1.4%) unrelated individuals with ataxia had combined CTA/CTG repeat expansions >100 compared to 1/1190 (0.08%) healthy controls (P < 0.0005); (ii) neuropsychological assessment revealed a dysexecutive syndrome among SCA 8 patients, not readily explained by motor or mood disturbance; neuropsychiatric symptoms occurred commonly; (iii) cerebellar atrophy was the only salient MRI abnormality in the patient group.

CONCLUSIONS

The SCA 8 expansion is associated with ataxia in Scotland. The disorder is associated with a dysexecutive syndrome.

Association of MUTYH and colorectal cancer

Mutations in the MUTYH gene have been reported to be associated with increased risk of developing colorectal cancer. In this study, we confirmed this association using original data on 928 colorectal cancer cases and 845 healthy controls from Scotland. We then conducted a meta-analysis from published data on the association between mutations at MUTYH and colorectal cancer risk. We show for the first time a small but significant mono-allelic effect with a genotype relative risk (GRR) of 1.27 (95% confidence interval (CI): 1.01-1.61), and confirm and give a more precise estimate of the strong bi-allelic effect with an estimated GRR of 117 (95% CI: 74-184). This study underscores the need for large sample sizes in order to identify small gene effects when the disease allele frequency is low.

Renpenning syndrome comes into focus

Renpenning syndrome represents a prototypic X-linked mental retardation condition with full expression of the phenotype in males and little or no expression in females. The predominant clinical findings are microcephaly, long narrow face, short stature with lean body build, and small testes. Mental retardation, usually of severe degree, occurs in 95% of cases. Less than 20% of cases have major malformations, the most common being cardiac defects and cleft palate. Subsequent to the description of mutations in the polyglutamine tract binding protein 1 (PQBP1) in Sutherland-Haan syndrome, Hamel cerebropalatocardiac syndrome, MRX55, and two small XLMR families, a single nucleotide insertion has been found in the original family with Renpenning syndrome and an AGAG deletion in a second family with the Renpenning syndrome. Mutations have also been found in Golabi-Ito-Hall syndrome, Porteous syndrome, and an additional small family. It is now demonstrated that five named XLMR syndromes (Sutherland-Haan, Hamel cerebropalatocardiac, Golabi-Ito-Hall, Porteous, and Renpenning), one nonsyndromic family (MRX55), and three small XLMR families have PQBP1 mutations and are thus allelic XLMR entities. In acknowledgement of the historical importance of the original report of Renpenning syndrome [1962], we propose that the entities with PQBP1 mutations be combined under the name of Renpenning syndrome.

Patient satisfaction with two different models of cancer genetic services in south-east Scotland

There is a need to integrate primary- and secondary-care cancer genetic services, but the most appropriate model of service delivery remains unclear. This study reports patients' expectations of breast cancer genetic services and a comparison of their satisfaction with two service models. In the first model, risk assessment was carried out using mailed family history data. Women estimated as being at high/moderate risk were offered an appointment at the familial breast cancer clinic, and those at low risk were sent a letter of reassurance. In the second model, all women were seen by a genetic nurse specialist, who assessed risk, referred high/moderate-risk women to the above clinic and discharged those at low risk. Over 60% of all women in the study regarded access to breast screening by mammogram and regular check-ups as very important. This underlines the demand for a multidisciplinary service providing both clinical genetic and surgical services. Satisfaction was high with both models of service, although significantly lower among women not at increased cancer risk and thus not offered a clinical check-up and mammography. Increased cancer worry was associated with a greater expressed need for information and for reassurance through follow-up clinical checks and mammography. Better targeting of counselling to the expressed concerns and needs of these women is required to improve the service offered. GPs and patients expressed no clear preference for any specific service location or staffing configuration. The novel community service was less expensive in terms of both staff and patient costs. The potential to decrease health staff/patient contact time and to employ nurse practitioners with both clinical genetic and oncology training should be explored further. The rapidly rising demand for these services suggests that the evaluation of further new models needs to continue to be given priority to guide the development of cancer genetic services.

Spinocerebellar ataxia type 8 in Scotland: genetic and clinical features in seven unrelated cases and a review of published reports

OBJECTIVES

To establish whether the DNA expansion linked to spinocerebellar ataxia type 8 (SCA 8) is associated with ataxia in Scotland; to clarify the range of associated clinical phenotypes; and to compare the findings with previous reports.

METHODS

DNA was screened from 1190 anonymised controls, 137 subjects who had tested negative for Huntington's disease, 176 with schizophrenia, and 173 with undiagnosed ataxia. Five unrelated ataxic patients with the SCA 8 expansion and a sixth identified subsequently had clinical and psychometric assessment; the clinical features were available in a seventh. A systematic search for other reports of SCA 8 was undertaken.

RESULTS

Over 98% of SCA 8 CTA/CTG repeat lengths fell between 14 and 40. Repeat lengths over 91 were observed in three healthy controls (0.12%), two patients with suspected Huntington's disease (0.73%), and six ataxic subjects (1.74%; p<0.0005 v healthy controls). Repeat lengths over 100 occurred in five ataxic subjects but in only one control. All seven symptomatic subjects with the SCA 8 expansion had a cerebellar syndrome; four had upper motor neurone signs; and 5/6 assessed had cognitive complaints. There was personality change in two and mood disturbance in three. In published reports, SCA 8 repeat lengths over 91 occurred in approximately 0.5% of the healthy population but were over-represented among ataxic patients (3.4%; p<0.0001). The predominant clinical phenotype was cerebellar, with pyramidal signs in 50%, and neuropsychiatric features in some cases.

CONCLUSIONS

SCA 8 expansion is a risk factor for a cerebellar syndrome, often associated with upper motor neurone and neuropsychiatric features. The expansion occurs unexpectedly often in the general population.

A randomised controlled trial of a psychoeducational intervention for women at increased risk of breast cancer

This study aimed to compare the impact of two versions of a psychoeducational written intervention on cancer worry and objective knowledge of breast cancer risk-related topics in women who had been living with an increased risk of familial breast cancer for several years. Participants were randomised to three conditions: scientific and psychosocial information pack (Group 1), scientific information pack only (Group 2) or standard care control (Group 3). They completed postal questionnaires at baseline (n=163) and 4 weeks (n=151). As predicted, there was a significant decrease in cancer worry for Group 1, but not Group 2. Objective knowledge significantly improved for both Group 1 and Group 2 as expected, but not Group 3. However, there was an unpredicted decline in cancer worry for Group 3. This study supports the value of a scientific and psychosocial information pack in providing up-to-date information related to familial risk of breast cancer for long-term attendees of a familial breast cancer clinic. Further research is warranted to determine how the information pack could be incorporated into the existing clinical service, thus providing these women with the type of ongoing psychosocial support that many familial breast cancer clinics are currently lacking.

Referrals of women with a family history of breast cancer from primary care to cancer genetics services in South East Scotland

As part of a cluster randomised trial to assess an alternative model of cancer genetics services, we gathered data on all referrals from general practitioners (GPs) to cancer genetics services in South East Scotland over a 4-year period. The referral rate per 1000 patients rose by 48% from 0.21 in the 2-year period before the trial to 0.31 during the trial. This increase was much greater in the trial group offered the GP clinic service (64% increase compared to a 38% increase in those referred to the regional service). Thus, the offer of a more local service appeared to have a marked effect on GP management of these women. Referral rates to cancer genetics services from general practices varied widely with higher referral rates from practices with more female partners. There was a negative correlation between referral rates and practice area deprivation scores. However, this was not found during the trial in the group which offered clinics in general practice, the provision of clinic appointments nearer to the homes of more socially deprived women resulting in improved access to women from deprived areas. The interaction with the GP appears to be associated with an inappropriate level of interest in and expectation of the appropriateness of genetic testing. The provision of the clinics within general practice did not result in higher levels of confidence among GPs in managing these women.

Is it acceptable to approach colorectal cancer patients at diagnosis to discuss genetic testing? A pilot study

In this pilot study, the acceptability of approaching 111 newly diagnosed colorectal cancer patients with the offer of genetic testing for hereditary nonpolyposis colorectal cancer (HNPCC) was assessed. A total of 78% of participants found it highly acceptable to have the information about HNPCC brought to their attention at that time.

A randomised controlled trial of breast cancer genetics services in South East Scotland: psychological impact

This study compared the psychological impact of two models of breast cancer genetics services in South East Scotland. One hundred and seventy general practices were randomised to refer patients to the existing standard regional service or the novel community-based service. Participants completed postal questionnaires at baseline (n=373), 4 weeks (n=276) and 6 months (n=263) to assess perceived risk of breast cancer, subjective and objective understanding of genetics and screening issues, general psychological distress, cancer worry and health behaviours. For participants in both arms of the trial, there were improvements in subjective and objective understanding up to 4 weeks which were generally sustained up to 6 months. However, improvements in subjective understanding for the women at low risk of breast cancer (i.e. not at significantly increased risk) in the standard service arm did not reach statistical significance. Cancer worry was significantly reduced at 6 months for participants in both arms of the trial. The two models of cancer genetics services tested were generally comparable in terms of the participants' psychological outcomes. Therefore, decisions regarding the implementation of the novel community-based service should be based on the resources required and client satisfaction with the service.

Hereditary haemorrhagic telangiectasia: a questionnaire based study to delineate the different phenotypes caused by endoglin and ALK1 mutations

BACKGROUND

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia characterised by mucocutaneous telangiectasis, epistaxis, gastrointestinal haemorrhage, and arteriovenous malformations in the lung and brain. Causative mutations for HHT have been identified in two genes, endoglin and ALK1, which encode proteins involved in serine-threonine kinase signalling in the endothelial cell.

METHODS

A number of people affected with HHT had completed a postal questionnaire as part of an international study to delineate the HHT phenotype. We identified questionnaires completed by subjects in whom we had identified a mutation in endoglin or ALK1. Further questionnaires were sent to families with known mutations. Data were only included from questionnaires returned by people known to carry disease causing mutations.

RESULTS

Questionnaires were completed by 83 subjects with known mutations. Of these, 49 had endoglin mutations (HHT1) and 34 had ALK1 mutations (HHT2). Subjects with HHT1 reported an earlier onset of epistaxis (p=0.01) and telangiectasis (p=0.0001) than those with HHT2. Pulmonary arteriovenous malformations were only reported in the endoglin mutation group in our study (p<0.001).

CONCLUSIONS

Our questionnaire based study provides evidence that the HHT phenotype caused by mutations in endoglin (HHT1) is distinct from, and more severe than, HHT caused by mutations in ALK1 (HHT2). This has significant implications for diagnosis, screening, and treatment in the two different forms of HHT, as well as for understanding the pathogenesis of the disease.

Population carrier frequency of hMSH2 and hMLH1 mutations

Knowledge of population carrier frequency for DNA mismatch repair (MMR) gene mutations would contribute to understanding the burden of cancer due to genetic susceptibility, but robust prevalence estimates are lacking. To estimate carrier frequency, we genotyped a cohort of relatives of mutation carriers and determined their colorectal cancer prevalence. Systematic Finnish and US data were combined with Scottish genotype and cancer prevalence data in a Bayesian calculation. The estimated carrier prevalence in the population aged 15-74 years is 1:3139 (95% Cl = 1:1247-1:7626) and these carriers are at high risk of colorectal and other cancers.

Evidence based medicine in practice: lessons from a Scottish clinical genetics project

OBJECTIVE

To establish national clinical guidelines and integrated care pathways for five conditions (tuberous sclerosis (TS), Huntington's disease (HD), myotonic dystrophy (MD), neurofibromatosis type 1 (NF1), and Marfan syndrome (MS)) and audit their use in Scotland.

DESIGN

Systematic review of published reports followed by consensus conferences to prepare clinical guidelines and integrated care pathways. Structured review of medical records before and after introduction of integrated care pathways to document changes in practice. Survey of staff views on procedures adopted.

SETTING

All four clinical genetics centres in Scotland.

RESULTS

Project resulted in reduced variation in practice across centres, improved data recording in medical records, and improved communication with other professional groups. A very poor evidence base for management of patients with the conditions studied was found.

CONCLUSIONS

A collaborative structure for undertaking clinical research would improve the evidence base for current practice. National discussion of the boundaries of responsibility of care for the long term management of patients with these disorders is required. The integrated care pathway approach shows promise as a means of facilitating the development of audit within clinical genetics services.

GPs' views on their role in cancer genetics services and current practice

BACKGROUND

Increasing demand for cancer genetics services has necessitated an urgent review of how these services are organized and, in particular, identification of an effective role for primary care.

OBJECTIVES

We aimed to assess the views of GPs on their role in cancer genetics services and their confidence in performing that role; to assess their understanding of cancer genetics, current practice and referral behaviour; and to identify needs for information and training to enable GPs to play an effective role in these services.

METHOD

A cross-sectional questionnaire survey of GPs was conducted through general practices in SE Scotland; 397 (response rate 59.3%) GPs returned a completed questionnaire. Outcome measures were: responders' perceptions of their role in cancer genetics services; confidence within that role; understanding of cancer genetics; current practice regarding patients presenting with concerns about their family history of cancer; and perceived information and training needs.

RESULTS

GPs identified their role to be: taking a family history; making appropriate referrals to specialist services; providing emotional support; teaching breast self-examination; and discussing need for screening. Lack of confidence within this role was reflected in low levels of understanding of cancer genetics and in inappropriate referral practices. Concerns were expressed about the increasingly specialist role demanded of primary care. A desire for referral guidelines and community genetics clinics was identified.

CONCLUSIONS

GPs readily identify a role for themselves in cancer genetics services, but admit to a lack of confidence in this area, calling for clear referral guidelines and specialist community support. Current inappropriate referral to specialist services results from a lack of confidence in estimating cancer risk, highlighting the need for the development of clear referral criteria. Given the rapidly increasing demand for cancer genetics services and the vital role of primary care, it is important to identify a model of these services that facilitates effective involvement of GPs without further increasing their workload.

Guidelines and care pathways for genetic diseases: the Scottish collaborative project on tuberous sclerosis

In Scotland a national audit project has been undertaken to devise evidence-based guidelines for the clinical management of patients with tuberous sclerosis (TS), a dominantly inherited multisystem disorder. In order to facilitate the audit and use of these guidelines a 'Care Pathway' was devised to form the patient records. We describe the process of guideline development for TS and our TS Care Pathway.

Dentatorubral and pallidoluysian atrophy (DRPLA). Clinical and neuropathological findings in genetically confirmed North American and European pedigrees

Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant disorder that clinically overlaps with Huntington's disease (HD) and manifests combinations of chorea, myoclonus, seizures, ataxia, and dementia. DRPLA is caused by a CAG triplet repeat (CTG-B37) expansion coding for polyglutamine on chromosome 12 and exhibits the genetic phenomenon of anticipation. This neurodegenerative disease has only rarely been reported in non-Japanese pedigrees, and there are only a few neuropathological studies in genetically confirmed patients. We report 10 cases of DRPLA from two North American and two British pedigrees in which CTG-B37 expansions have been demonstrated within each kindred (54-83 repeats), individually in 8 of the 10 cases, and describe the neuropathological findings in 4 cases. Members of DRPLA kindreds have a wide range of clinical phenotypes and markedly variable ages at onset. The neuropathological spectrum is centered around the cerebellifugal and pallidofugal systems, but neurodegenerative changes can be found in many nuclei, tracts, and systems. Evidence of CTG-B37 triplet repeat expansion should be sought in HD-like cases that are negative for expanded triplet repeats within the HD IT15 gene or in autopsy cases with degeneration of the dentatorubral or pallidoluysian systems.

A study of the Huntington's disease associated trinucleotide repeat in the Scottish population

Accurate measurements of a specific CAG repeat sequence in the Huntington's disease (HD) gene in 337 HD patients and 229 normal controls from the Scottish population showed a range from 35 to 62 repeats in affected subjects and eight to 33 in normal subjects. A link between early onset of symptoms and very high repeat number was seen. For HD patients with the most common affected allele sizes (39 to 42 repeats) absolute repeat size was a poor index for the age at onset of symptoms. There was variability in the transmitted repeat size for both sexes in the HD size range. We observed a significant increase of repeat size for paternal transmission of the disease and greater instability for paternally transmitted CAG repeats in the HD size range.

Evidence for involvement of a second genetic locus on chromosome 11q in porphyrin metabolism

Chester porphyria is a distinct type of acute porphyria, which shows a biochemical overlap with acute intermittent and variegate porphyrias and has a dual enzyme deficiency of porphobilinogen deaminase (PBGD) and protoporphyrinogen oxidase. Linkage analysis in an extensive family with Chester porphyria was undertaken using multiple polymorphic markers. A maximum two point Lod score of 5.25 at 0.07 recombination (confidence interval 0.01 to 0.14) was observed with D11S351, which has been localised to 11q23.1. Multipoint linkage analysis confirmed the two point results and gave a maximum Lod score of 7.33 at a distance less than 1 cM proximal to D11S351. PBGD also maps to 11q but four recombinants could be identified from ten informative meioses in this family using a PBGD DNA polymorphism. Thus, a separate locus on 11q appears to be the basis of Chester porphyria.

Evidence for genetic heterogeneity in hereditary hydronephrosis caused by pelvi-ureteric junction obstruction, with one locus assigned to chromosome 6p

Hereditary hydronephrosis (MIM 143400) is an autosomal dominant trait that causes unilateral or bilateral pelvi-ureteric junction (PUJ) obstruction. Linkage analysis was undertaken in 5 families with hereditary PUJ obstruction using the major histocompatibility complex locus as a test marker. The data as a whole supported a hereditary hydronephrosis locus on 6p. Maximal lod scores were 3.090 at a recombination fraction of 0.1 with full penetrance, and 2.486 at a recombination fraction of 0.1 with a penetrance of 90%. However, analysis of two point lod scores using the HOMOG program revealed significant evidence for genetic heterogeneity with one locus on 6p in 4 of the families, and a different locus in one family. After exclusion of this unlinked family, two point analysis gave a maximal lod score of 3.9 at a recombination fraction of 0.05 with full penetrance, and 4.2 at a recombination fraction of 0.0 with 90% penetrance. These data support the assignment of one of the loci for hereditary hydronephrosis to chromosome 6p.

Association of less common cystic fibrosis mutations with a mild phenotype

A majority of cystic fibrosis (CF) genes (70 to 75%) share a single mutation, but the remaining 25 to 30% of defects are accounted for by more than 20 different mutations. One of the less frequent mutations, G551D, has been identified in the CF genes of two sibs and one unrelated adult patient. The adult patient also has a second rare mutation, delta I507. All three subjects exhibit a less severe phenotype than that normally associated with CF. This supports a hypothesis that the common mutation (delta F508) is responsible for the severe form of the disorder, and the minority of patients with a milder form tend to have mutations at other sites in the CF gene.

Hazards to bladder and intestinal tissues from intravesical underwater electrical discharges from a surgical electronic lithoclast

Previous studies have shown that electronic lithoclast discharges produce effects resembling an underwater explosion. It was predicted that the shock wave produced by each discharge could damage nearby gas-containing gut through a mechanism known to be associated with underwater detonations. Effects associated with rapid oscillation of the vapour bubble produced could cause damage to the wall of the bladder. Investigation of lithoclast discharges in vivo on goat, and in vitro on sheep bladders demonstrated perforation of both. In vitro studies in the rabbit demonstrated the predicted greater susceptibility of air-filled gut over that filled with fluid. These hazards would be even greater in the ureter and caution in the use of electronic fragmentation of vesical and ureteric calculi is urged in the light of these findings.