Managing genetic discrimination: strategies used by individuals found to have the Huntington disease mutation.

The introduction of predictive testing for Huntington disease (HD) over 20 years ago has led to the advent of a new group of individuals found to have the HD mutation that are currently asymptomatic, yet destined in all likelihood to become affected at some point in the future. Genetic discrimination, a social risk associated with predictive testing, is the differential treatment of individuals based on genotypic difference rather than physical characteristics. While evidence for genetic discrimination exists, little is known about how individuals found to have the HD mutation cope with the potential for or experiences of genetic discrimination. The purpose of this study was to explore how individuals found to have the HD mutation manage the risk and experience of genetic discrimination. Semi-structured individual interviews were conducted with 37 individuals who were found to have the HD mutation and analysed using grounded theory methods. The findings suggest four main strategies: "keeping low", minimizing, pre-empting and confronting genetic discrimination. Strategies varied depending on individuals' level of engagement with genetic discrimination and the nature of the experience (actual experience of genetic discrimination or concern for its potential). This exploratory framework may explain the variation in approaches and reactions to genetic discrimination among individuals living with an increased risk for HD and may offer insight for persons at risk for other late-onset genetic diseases to cope with genetic discrimination.

SCA-2 presenting as parkinsonism in an Alberta family: clinical, genetic, and PET findings.

The authors describe an Alberta family with levodopa-responsive parkinsonism without cerebellar abnormalities. Genetic testing showed expanded repeats for SCA-2; other mutations for parkinsonism were excluded. The expanded allele shows interruption of the CAG repeat with CAA. PET in two affected members showed reduced fluorodopa uptake in striatum and normal raclopride binding. Families with autosomal dominant, levodopa-responsive parkinsonism should be tested for the SCA-2 mutation.

Cognitive manifestations of Huntington disease in relation to genetic structure and clinical onset.

OBJECTIVE: To examine the cognitive manifestations of Huntington disease (HD) with respect to age, clinical onset, progression, and genetic analyses. DESIGN: Case series of people with HD or at risk (AR) for HD. SETTING: Movement disorders and medical genetics clinics. PARTICIPANTS: Volunteer sample of 50 patients with HD and 127 AR adults. MEASURES: Neuropsychological evaluation was conducted with multiple measures of cognitive function (intelligence, memory, attention, executive, spatial, language), strength, manual speed/dexterity, somatosensory function, and mood. Quantitative molecular genetic analysis by means of polymerase chain reaction was conducted on 31 patients with HD and 86 AR subjects. RESULTS: In clinical HD, cognitive impairment correlated with number of years affected but not age at onset. The linear regression had a negative intercept, suggesting impaired cognitive function by the time of onset. In AR gene carriers, lower cognitive performance correlated with more trinucleotide repeats. In clinical HD, trinucleotide repeats interacted with disease chronicity such that more repeats were associated with worse performance over time; the overall effect of this was small compared with the effect of disease chronicity alone. Except for one AR subject, mood state was not associated with cognitive performance in either patients with HD or AR subjects. CONCLUSIONS: Cognitive decline appears to start before clinical onset of HD and is correlated with the number of trinucleotide repeats. Subsequent cognitive decline is primarily a function of number of years affected, although there is evidence that the presence of more trinucleotide repeats is associated with faster deterioration.

Multidisciplinary approach to management of a hereditary neurodegenerative disorder: Huntington disease.

Huntington Disease is a well known autosomal dominant inherited disease resulting in emotional problems, abnormalities of movement, and eventually dementia. It stands out as one of the most devastating illnesses, not only for its neurodegenerative progression but also for its impact on families. Care often becomes fragmented due to the person's response to symptoms and/or family breakdown. The successful interaction of health care disciplines working with Huntington Disease in our centers, namely, the family physicians, nursing, Genetics, Neurology, Psychiatry, Social Work, and Long Term Care has resulted in a comprehensive program of care for our patients and their families. This article will describe the history, structure and interaction of the multidisciplinary group. It will describe the difficulties we have overcome and offer suggestions for the implementation of similar programs for the care of people with other disorders.

Ethical, social and legal issues in Huntington disease: the nurse's role.

The nurse's role will be discussed in relation to the issues which may present as the result of our ability to use predictive tests for neurodegenerative disease. Huntington disease is an autosomal dominant inherited disease, characterised by emotional problems, abnormalities of movement and dementia. The disease is slowly progressive leading to a severely debilitated state and finally death in ten to twenty years. In 1983, DNA testing became available for persons at risk for Huntington disease and for confirmation of diagnosis for those showing symptoms. The availability of testing presents many ethical, social and legal issues for persons at risk, health care professionals and other segments of society. This paper will briefly review the genetic transmission and profession of Huntington disease. It will outline some of the benefits as well as some of the risks and problems DNA testing presents.

Relationship between trinucleotide repeats and neuropathological changes in Huntington's disease.

The discovery of the Huntington's disease (HD) gene has provided the impetus to determine the association between the triplet repeat sequences and clinical manifestations of the disease. The present study is directed toward determining the relationship between the triplet repeat sequences and severity of the neurodegenerative process. Nineteen HD postmortem cases were evaluated for neuropathological changes as well as for the number of trinucleotide repeat sequences, each in a blinded fashion. Each case was assigned a gross grade according to the scale of Vonsattel and colleagues (1985); neuronal counts were then performed on both the caudate and the putamen. For 7 of the postmortem cases, blood had been collected prior to death and was analyzed for the HD gene. For the 12 remaining cases for which blood was unavailable, DNA from the frontal neocortex and striatum was extracted from frozen or formalin-fixed paraffinized tissue and subsequently analyzed for the HD gene. When correlation was made for age at death, greater numbers of trinucleotide repeats were associated with greater neuronal loss, in both the caudate (r = 0.9641, p < 0.001) and the putamen (r = 0.9652, p < 0.001). When correction was made for disease duration, the correlation was again significant, for both the caudate (r = 0.6396, p < 0.01) and the putamen (r = 0.6710, p < 0.001). This suggests that in HD, longer trinucleotide repeat length is associated with a faster rate of deterioration and greater pathological severity. A comparison of trinucleotide repeat length in different brain regions in 4 of the HD postmortem cases associated with greater numbers of repeats consistently demonstrated fewer repeats in the cerebellum than in the frontal cortex, striatum or blood.

Familial caudal dysgenesis: evidence for a major dominant gene.

Four sibs with varying degrees of caudal dysgenesis are described. Case 1 showed aberrant umbilical cord vasculature with a single umbilical artery near the placental insertion. Cases 2 and 3 showed full sirenomelia, one with a complex congenital heart defect. Case 4 had an imperforate anus and an excessively long umbilical cord. The father's half-sib had an imperforate anus, rectovaginal fistula and genitourinary anomalies. A dominant gene with reduced penetrance is likely.