Sheila A. Simpson

Family Communication about Genetic Risk: The Little That Is Known

Although family communication is important in clinical genetics only a small number of studies have specifically explored the passing on of genetic knowledge to family members. In addition, many of these present exploratory or tentative findings based upon small sample sizes, or data collected only a short time after testing. Nevertheless, if health professionals are to develop effective strategies to help patients’ deal with communication issues, we need to know more about what actually happens in families. The aim of this commentary is to identify factors which appear to influence whether patients share information about genetic risk with relatives who are unaware of that risk, with whom they share it and how they go about it. The paper draws upon evidence and thinking from the disciplines of psychology (including family therapy), sociology, medicine and genetic counselling. It is presented under the following headings: disease factors, individual factors, family factors and sociocultural factors. It concludes by highlighting a number of key issues which are relevant for health professionals.

Mutations in XPR1 cause primary familial brain calcification associated with altered phosphate export

Primary familial brain calcification (PFBC) is a neurological disease characterized by calcium phosphate deposits in the basal ganglia and other brain regions and has thus far been associated with SLC20A2, PDGFB or PDGFRB mutations. We identified in multiple families with PFBC mutations in XPR1, a gene encoding a retroviral receptor with phosphate export function. These mutations alter phosphate export, implicating XPR1 and phosphate homeostasis in PFBC.

Predictive DNA-testing for Huntington's disease and reproductive decision making: a European collaborative study

This European collaborative study addresses the question whether a predictive test result for Huntingtons disease (HD) has an effect on subsequent reproduction by comparing carriers and non-carriers of the Huntington mutation. A unique characteristic of this study is that this evaluation is done in persons at reproductive age who had a predictive test after the identification of the Huntington gene and who were counselled in one of the participating centres. Data were collected for 180 carriers and 271 non-carriers who received a predictive test result in the period 1993–1998 in Aberdeen, Athens, Cardiff, Leiden, Leuven, Paris or Rome. The mean age of the total study group was 31.5 years and for about half of the group the follow-up interval was 3 years or more, with a maximum of 7 years. The collaborative study clearly revealed an overall impact of the predictive test result on subsequent reproduction: 14% of the carriers had one or more subsequent pregnancies vs 28% of the non-carriers. In the total carrier group a prenatal test was carried out in about two thirds of the pregnancies and one child was born after preimplantation genetic diagnosis; artificial insemination by donor, egg cell donation or adoption were not reported. A more refined analysis was performed in the subgroup with a follow-up interval of at least 3 years and who reported ‘family planning’ as a motive to apply for predictive testing in the pretest period. The complexity of this motive is discussed. In this subgroup with a desire for children in the pretest period the effect of the predictive test result was more pronounced: 69% of the non-carriers had subsequent pregnancies while only 39% of the carriers who mentioned ‘family planning’ as one of the major reasons to apply for predictive testing had a subsequent pregnancy. Of the carriers with one or more subsequent pregnancies the percentage using prenatal diagnosis was slightly higher than the percentage not using it, although there were clear differences from one centre to another. The latter groups decisions may seem more intriguing but may be partially understood based on stage theories of health behaviour. Last, but not least, whatever option is chosen by a couple at increased risk of transmitting the Huntington mutation, it is of the utmost importance that professionals fully respect this decision and support the couple.

Reduced penetrance alleles for Huntington’s disease: a multi-centre direct observational study

Objective: To obtain penetrance data for Huntington’s disease when DNA results are in the range of 36–39 CAG repeats and assess the consistency of reporting the upper allele from two reference centres. Method: Data were collected anonymously on age of onset or age last known to be unaffected from a cohort of individuals with results in this range. DNA samples were re-analysed in two reference centres. Kaplan-Meier analysis was used to construct an age of onset curve and penetrance figures. Results: Clinical data and concordant DNA results from both reference centres were available for 176 samples; penetrance figures (and 95% confidence intervals) for this cohort, at age 65 and 75 years, were 63.9% (55.5% to 73.2%) and 74.2% (64.2% to 84.2%), respectively. Inclusion of 28 additional subjects for whom repeat DNA results were unavailable, obtained from only one reference centre, or discrepant by one repeat within this range, gave penetrance data (including 95% confidence intervals) at ages 65 and 75 years of 62.4% (54.4% to 70.4%) and 72.7.% (63.3% to 82.1%), respectively. 238 duplicate results were available from the reference centres; 10 (4.2%) differed by one CAG repeat in the reporting of the upper allele and in two (0.84%) of these cases the discrepancy was between 39 and 40 repeats. Conclusion: When DNA results are in this range, a conservative approach is to say that there is at least a 40% chance the person will be asymptomatic at age 65 years and at least a 30% chance the person will be asymptomatic at age 75 years.

Young people's experiences of growing up in a family affected by Huntington's disease

Previous research and clinical experience suggest that Huntington’s disease (HD) can considerably affect family life, particularly for young people (YP) at risk. The goal of this study was to describe the experiences of YP from families affected by HD. YP were identified through the regional genetics clinic and the Scottish Huntington’s Association. In‐depth interviews were used to explore YP’s experiences of finding out about HD in the family; perceptions of their own risk; caring activities; protective or risk factors; and the impact of HD on relationships with siblings, parents, extended family members, and the wider community. Thirty‐three YP between the ages of 9 and 28 years were interviewed. A qualitative thematic analysis was undertaken. The analysis revealed four main themes: YP as carers, the worried well, those who cope, and those at risk/in need. These themes highlight the varied experience of growing up in a family affected by HD. Whilst some YP successfully coped, others experienced considerable problems and were at risk of physical and/or emotional harm. In understanding why some cope better than others, our findings suggest protective and risk factors within these themes. In particular, participants who grew up knowing about HD from an early age seemed to cope better.

Prenatal testing for Huntington's disease: a European collaborative study.

This European study involving seven genetic centres from six countries – Aberdeen, Cardiff (UK), Leiden (Netherlands), Leuven (Belgium), Paris (France), Rome (Italy), Athens (Greece) has gathered information on prenatal testing by direct mutation analysis and exclusion testing for Huntingtons disease (HD) from the six European countries during the period 1993–1998. Data describing the parent belonging to the HD family was collected; this included their sex and age as well as their risk of developing HD. Information about previous pregnancies, the rank of the pregnancy being tested and its outcome was also gathered. In addition the number of previous prenatal tests for HD was recorded. Three hundred and five results were recorded by the participating countries between 1993 and 1998. The largest groups came from the UK (157) and the Netherlands (90). The mean age for the parent from the HD family was 30.8 years. In half of the tests the prospective parent was an asymptomatic gene carrier, 42% remained at risk, and 6% of the prospective parents were already showing clinical features of HD. 65% of tests performed used mutation analysis.

One hundred requests for predictive testing for Huntington's disease.

In Grampian region, the first 100 requests for predictive testing for Huntingtons disease have been analysed. Forty‐five presymptomatic predictive test results have been given, eleven families have made a decision to undergo prenatal exclusion tests, and so far eleven pregnancies have been investigated using chorion villus biopsy. This paper presents the protocol used and a descriptive analysis of those receiving results, those choosing to leave the programme, and those unable to complete it because of an unsuitable family structure or unco‐operative relatives.

Linkage in a family with X-linked Charcot-Marie-Tooth disease

The gene for the X‐linked form of Charcot‐Marie‐Tooth disease (CMT Peroneal Muscular Atrophy, X‐linked: McKusick No. 30280) has been shown in a single family to be linked to DXYSI with a lod score of 4.55 at a recombination fraction of 0.03 and to PGK1 with a lod score of 3.34 at zero recombination. This is in agreement with previous work based on several families. Pooled data from this family and 7 previously reported families give a maximum lod score of 12.04 at θmax of 0.05 for linkage between CMTX and DXYS1 loci.

How Do Partners Find out About the Risk of Huntington’s Disease in Couple Relationships?

Whilst a growing body of work has explored family communication about Huntington’s disease and how at-risk individuals learn about their risk, the experience of telling a partner and partners’ experiences of finding out about this potentially devastating hereditary illness have received little attention. This study describes the experiences of partners in finding out about Huntington’s disease and any impact on couple’s relationships/marriages. We undertook a thematic analysis of qualitative interviews which explored the dynamics of partners’ marriages after predictive testing and partners’ views of genetic counseling. A main theme from partners’ accounts was how they found out about their spouse’s risk of Huntington’s disease and the impact this had on marital relations. The analysis revealed four types of disclosure experiences: (1) marital secrets; (2) alerting, but not telling; (3) knowing and seeing; (4) marital ignorance. Our findings demonstrate that partners’ experiences of (non)disclosure about the risk of HD within marriages is an important factor which contributes to couples’ coping or marital problems. Exploring how spouses found out about their partner’s risk of HD will illuminate issues about a couple’s past and future patterns of communication and their coping strategies. A practical and ethical implication is the extent to which genetic counselors should inform partners about the course and nature of Huntington’s disease when a partner is the support person for the individual being tested.

New challenges for gamete donation programmes: Changes in guidelines are needed

In the UK, the Human Fertilisation and Embryology Act 1990 prevents children born as a result of donor-assisted conception from gaining access to identifying information about their genetic origins. There is growing concern that current screening protocols regarding gamete donation are ill-suited, especially in relation to genetic disease. There are no guidelines addressing the issues of confidentiality that might arise if a disease emerges after insemination and establishment of pregnancy. Donors may become aware that they are at risk of a familial condition after they have donated gametes or recipients of donated gametes may become aware of a genetic illness in the resulting child. At present, there is no agreed method for allowing this information to be given to the donor or other recipients of gametes from that person. We suggest that these issues should be raised with donors, and appropriate counselling and predictive tests offered to them. Changes in regulations regarding gamete donation should be considered that accommodate recent and possible future developments in genetics. Furthermore, consideration should be given to the storage of samples of DNA from donors for the future provision of genetic information.