Using a roster and haplotyping is useful in risk assessment for persons with intermediate and reduced penetrance alleles in Huntington disease.

The risk of a person having a child with an inherited disorder, caused by an unstable triplet repeat, such as Huntington disease (HD), depends on the expansion of the mutation in that person, which is connected both to the biological nature of the mutation and to the person's relation to the carrier of the full mutation. Once the mutation causing HD was identified, we were able to diagnose sporadic patients. A sporadic patient can sometimes be connected to a known HD pedigree by using a roster. By haplotyping and calculating the posterior identity-by-descent probability, we could establish whether a connection was coincidental or not. Furthermore, we describe the frequency of intermediate and reduced penetrance alleles detected. Using the family history and the roster to search for a connection, we examined whether these alleles were on the HD haplotype of a family. It is important to know the origin of an intermediate or reduced penetrance allele because if it comes from an HD branch of the family or from the non-HD affected side of the pedigree, different risks for relatives and penetrance ensue. In our study, most intermediate alleles came from the non-HD-affected side of the pedigree and had a repeat size in the lower range with a negligible risk for expansion. Intermediate alleles on the HD haplotypes were larger and found in predictive test applicants from known families or relatives from new mutations with a higher risk for expansion. Reduced penetrance alleles in the higher range were mainly found in symptomatic and predictive test applicants from known families, with a considerable risk for penetrance, although at older age. We conclude that a roster, a thorough family history, and haplotyping in persons with intermediate and reduced penetrance alleles are essential in considering the risk of a person having (a child with) HD.

Paradox of a better test for Huntington's disease.

OBJECTIVES: To describe the consequences of the identification of the Huntington's disease (HD) mutation on predictive and prenatal testing. METHODS: A retrospective study was performed considering the test applicants, procedures, and results before and after the identification of the mutation. 1032 people at risk for Huntington's disease in The Netherlands were included, of whom 741 applied for the predictive test in the period 1987 to 1997 in Leiden at the Department of Clinical Genetics, and after 1994, also in the other seven clinical genetics departments in The Netherlands. Uptake, sociodemographic variables, and test results, taken before and after the mutation was identified, are described. RESULTS: The uptake of the predictive test in the period studied was 24% and for the prenatal test 2%. No differences were noted in numbers and sociodemographic data between the period before and after the mutation was identified. After an initial increase in test applicants, a decrease was seen after 1995. After 1993 a significant increase of 25% at risk test applicants and a significant decrease of prenatal exclusion tests was noticed. Only 7% asked for reassessment by mutation analysis. New problems arose after the identification of the mutation, such as the option of reassessing the risk obtained by linkage analysis, direct mutation testing of 25% at risk persons with a parent who does not wish to know, new choices regarding reproduction, and new uncertainties for carriers of intermediate and reduced penetrance alleles and for their offspring and relatives. CONCLUSIONS: Although predictive testing has become reliable and available for every person at risk since the mutation has been identified, the uptake of predictive and prenatal tests fell short of expectation, no change in sociodemographic variables was seen, and a decrease in number of applicants was noted. Furthermore, new uncertainties, psychological problems, and questions arose.

Predictive testing of 25 percent at-risk individuals for Huntington disease (1987-1997).

Before the mutation causing Huntington disease was identified, predictive testing of 25% at-risk persons with a 50% at-risk parent who did not wish to know his/her genetic status, was only possible by exclusion testing. The exclusion test, using linked markers, ensures the parent's wish not to know because the parent's risk is not changed. When mutation analysis became available in 1993, new testing options for 25% at-risk persons emerged: viz., the exclusion-definitive test and direct mutation analysis. These new tests not only disclose the risk of the test candidate, but may also change the risk of the at-risk parent and siblings. The testing options for 25% at-risk test applicants and their consequences are discussed and the testing procedures and results of testing 64 25% at-risk persons in the period 1987 to 1997 are described. Relatives received unsought information in 56% of the test procedures before and 34% after the mutation was identified. A decision tree and guidelines for predictive testing of 25% at-risk test applicants are proposed. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:662-668, 1999.

Two centuries of mortality in ten large families with Huntington disease: a rising impact of gene carriership.

To estimate the impact of the Huntington gene on mortality, we studied ten families with Huntington disease, whose records started before 1800. We investigated mortality from 1800 to 1997 in 257 carriers of the Huntington gene and 474 potential carriers. Follow-up extended from age 20 years to the date of death or end-of-study date. The observed deaths were compared with those expected on the basis of the general population, adjusted for sex, age, and calendar time. To study the influence of the family and parental transmission, we calculated hazard ratios adjusted for sex, probability of carrying the gene, and year of birth. In 25,013 person-years, 420 deaths occurred, whereas 278 deaths were expected [standardized mortality ratio = 1.5; 95% confidence interval (CI) = 1.4-1.7]. Excess mortality was confined to ages 40-70 years (standardized mortality ratio = 2.2; 95% CI = 1.9-2.4). To study the evolution of mortality over time in this age group, we calculated absolute mortality rates per calendar period. From 1800 onward, mortality rates in the general population continuously declined, but among the families with Huntington disease this decline was absent. There were only small differences in risk between families, and the relative risk for paternal over maternal transmission was 1.2 (95% CI = 0.9-1.5). Our main finding is that persons who carry the Huntington gene and reach middle age have not benefited from advances in medical care and overall increase in life expectancy.

Experience in prenatal testing for Huntington's disease in The Netherlands: procedures, results and guidelines (1987-1997).

We have performed 31 exclusion tests (43 per cent) and 41 direct tests (57 per cent) in 43 couples at risk, in the period 1987 to 1997 in Leiden, The Netherlands. This resulted in termination of 28 pregnancies (39 per cent), with an increased risk. In 28 couples (65 per cent), the woman was at risk. Prenatal testing in consecutive pregnancies (mean number: 3) was performed in 15 couples (35 per cent), with a mean time interval of 15 months. Parents should make an independent choice for (every) pregnancy, although most (86 per cent) did not change their initial choice. It is important that the position of children in the same family, of whom some know their status as a result of prenatal testing, whereas others remain at risk, is taken into consideration in counselling. The relative number of exclusion tests when compared with direct tests has diminished since the mutation was identified. The prenatal exclusion-definitive test (Fig. 1) was rarely used (2/72, 3 per cent). Nowadays, direct mutation testing of the fetus only is simpler and faster and the risk of disclosure of the genetic status of the at-risk parent is only 25 per cent. This test should therefore be offered as another option and included in the international guidelines. The uptake for prenatal testing is low: for 2 per cent of the at-risk persons, 11 per cent of the tested carriers and a small group of at-risk persons wishing not to be tested themselves, prenatal testing seems an acceptable choice regarding reproduction.

Intelligence indices in people with a high/low risk for developing Huntington's disease.

Intelligence in 20 presymptomatic subjects with an increased risk (> 95%) for carrying the gene for Huntington's disease (HD) was studied in a prospective, case-control, single blind study. No significant differences between the groups were detected for intelligence indices and subtest scores (Wechsler Adult Intelligence Scale). The high level of the performance IQ and the significant discrepancy between performance IQ and verbal IQ found in both the high risk and the low risk groups contrasted with our expectations based on anamnestic information, general clinical opinion, and the results of previously conducted studies. We propose that psychosocial circumstances could explain the test results and discuss the consequences of our findings for clinical genetics practice.

Juvenile Huntington disease in the Netherlands.

Juvenile Huntington disease (JHD) patients are distinguished from adult patients by an age at onset of less than 20 years. Investigating patients in our own database, we examined the proposition derived from studies in world literature that JHD should not be viewed as a separate clinical entity but rather as a manifestation of the rigid variant of the disease. Of 53 patients with JHD recorded in the Leiden Roster for Huntington Disease, relationships between sex, age at onset, duration of illness, maternal or paternal inheritance, motor symptom, first clinical features, and characteristics during the disease course, were obtained from the patients' files, and investigated. Although chorea is present in JHD, patients more often developed rigidity. Paternal inheritance, early dementia, epilepsy/myoclonus, and tremor during the disease course are confined for the most part to the rigid cases. A shorter duration of illness was evident in male patients with rigid JHD who inherited the disease from their father and developed their first disease feature at a younger age. The recognition of JHD as a distinct clinical entity does not appear to be warranted. Therefore, we propose, in accordance with other investigators, that rigid JHD be considered a clinical variant with special features.

Psychological effects of presymptomatic DNA testing for Huntington's disease in the Dutch program.

This study assessed the 6-month follow-up effects of presymptomatic DNA testing for Huntington's disease (HD) in 73 individuals at 50% prior risk who were identified either as carriers of the HD gene (N = 29) or as noncarriers (N = 44). The subject's knowledge of being a gene carrier was expected to induce intrusive emotions, denial-avoidance behavior, and pessimistic expectancies of the future and adjustment problems. The Impact of Event Scale, the Beck Hopelessness Scale, and the General Health Questionnaire were used as standard measures of psychological distress. At the disclosure of the test results, carriers had a strong increase in pessimistic expectations but showed a decline to baseline levels 6 months later. Noncarriers reported a steep decline in hopelessness compared with their pretest conditions but had increased scores after 6 months. Six months after the disclosure of the test results, both gene carriers and noncarriers reported a significant decrease in unwanted intrusive thoughts about HD. Carriers showed a slight increase in denial-avoidance behavior, whereas noncarriers showed a clear decrease. Our observations might indicate that tested individuals found relief from the prior psychological distress and that they were able to acknowledge the impact of the test result on their future. An unresolved question is how the foreknowledge will affect carriers as they approach the impending onset of the disease. Longer observation periods (> 6 months after disclosure) are required to study changes of the impact of DNA test results over time.

Dynamic mutation in Dutch Huntington's disease patients: increased paternal repeat instability extending to within the normal size range.

Analysis of the distribution of normal and expanded alleles of the polymorphic (CAG)n repeat in the IT15 gene in the Dutch population confirmed the presence of an expanded repeat on all Huntington's disease (HD) chromosomes. Our results show that the size distributions of normal and affected alleles overlap. Normal alleles range from 11 to 37 repeats and HD alleles contain 37 to 84 repeats. A clear correlation is found between age at onset and repeat length, but the spread of the age at onset in the major repeat range producing characteristic HD is too wide to be of diagnostic value. In the available parent-offspring pairs, maternal HD alleles show a moderate instability with a slight preponderance of size increase over size decrease. Paternal alleles have a bimodal distribution: the majority (69%) behave similarly to the maternal alleles, while the remainder (31%) show a dramatic expansion, the degree of which appears proportional to the initial size. This is shown in three out of four juvenile patients, who have repeats of 71, 74, and 84 copies, respectively, originating from expanded paternal HD alleles in the previous generation. Two sporadic cases are caused by expansion of 'large' normal paternal alleles of 32 and 34 repeats, respectively, to 46 copies. This not only confirms the diagnosis of HD in two de novo cases, but it also underlines the increased paternal instability. In addition paternal repeat instability was once detected within the normal range in two sibs who inherited 21 and 22 repeats, respectively, on the same paternal chromosome. In two Dutch HD families the segregation of the expanded (CAG)n repeat was found. Analysis of the (CAG)n repeat in our previously reported recombinants confirmed their disease status.

Presymptomatic DNA testing for Huntington disease: identifying the need for psychological intervention.

UNLABELLED: In the Dutch presymptomatic DNA-testing program for Huntington disease (HD), 29 individuals with increased risk and 44 with decreased risk were followed-up 6 months after test results. A prognostic model was built aimed at identifying individuals at risk for psychological maladjustment, as measured by the Impact of Event Scale, the Beck Hopelessness Scale, the General Health Questionnaire, and the Social Support Questionnaire. RESULTS: 1) The more that applicants suffered from intrusive feelings about HD and tried to avoid HD-related situations, prior to the test, the greater the chance that they will experience this 6 months after the test if they proved to be at increased risk; 2) the more that both individuals with increased risk and those with decreased risk who suffered from the threat of having HD tried to avoid HD-related situations prior to the test and the less satisfied they were with available support, the greater the probability that they will show avoidance behavior after the test; 3) the more pessimistic that individuals with increased risk as well as those with decreased risk were about their future prior to the test, the more they avoided HD-related situations and the more dissatisfied they were about their available support (pretest), the greater the probability that they will become depressive and suicidal. Psychological adjustment was also studied as a function of a) intrusion/denial-avoidance pattern over time and b) healthy mental functioning/future expectancies. Most individuals with increased risk (86%) seem to cope well thus far, although this was based largely on strong psychological defenses and dependent on satisfactory relationships.(ABSTRACT TRUNCATED AT 250 WORDS)

Defining the proximal border of the Huntington disease candidate region by multipoint recombination analyses.

The candidate region for the Huntington disease (HD) gene has been narrowed down to a 2.2-Mb region between D4S10 and D4S98 on the short arm of chromosome 4. To map the HD gene within this candidate region 65 Dutch HD families were studied. In total 338 informative meioses were analyzed and 11 multiple informative crossovers were detected. Assuming a minimum number of recombinations and no double recombinations, our multiple informative crossovers are consistent with one specific genetic order for 12 loci: D4S10-(D4S81, D4S126)-D4S125-(D4S127,D4S95)-D4S43-(D4 S115, D4S96, D4S111, D4S90, D4S141). This is in agreement with the known data derived from similar and other methods. The loci between brackets could not be mapped relative to each other. In our family material, two informative three-point marker recombination events were detected in the proximal HD candidate region, which are also informative for HD. Both recombination events map the HD gene distal to D4S81 and most likely distal to D4S125, narrowing down the HD candidate region to a 1.7-Mb region between D4S125 and D4S98.

Presymptomatic DNA-testing for Huntington disease: pretest attitudes and expectations of applicants and their partners in the Dutch program.

We studied the baseline attitudes, prior to testing, of 70 applicants at risk for Huntington disease (HD) and their partners in the Dutch presymptomatic DNA-testing program. Two thirds of the applicants were female; 36% already had children. The main reason (60%) for undertaking the test was for family planning. Other reasons were either to reduce uncertainty (43%) or to obtain certainty (38%). Partners of applicants stated that planning for the future was for them the most important reason (76%). Significantly more at-risk females (42%) than males (16%) anticipated an unfavorable test outcome. Quite remarkably, most applicants and partners denied that a positive result might have adverse effects on either personal mood, quality of life, or marriage. Only a few did not expect that a favorable result would induce relief. The eventual outcome of the test was expected to enable applicants to gain control over their future, whatever the results. Hence, we propose that the applicants form a self-selected group, based on their expectation that they will not be emotionally affected by either result.

Duration of illness in Huntington's disease is not related to age at onset.

The age at onset and duration of illness were studied in patients with Huntington's disease in the Leiden Roster which at 1 July 1990 contained 2787 patients. Of 1106 patients, 800 deceased and 306 alive, the age at onset was known. The median duration was 16.2 (range 2-45) years. In contrast to the current opinion, the median duration was independent of the age of onset. The median duration in juvenile Huntington's disease was 17.1 years, which is much longer than reported in the literature, and comparable with the categories for the age of onset of 20-34 and 35-49 years. Only in the group where onset was over 50 years of age was the median duration somewhat shorter (15.6 years), which can be ascribed to unrelated causes of death. As age of onset and duration of illness are not related, at least two mechanisms to determine the clinical course have to be postulated: one for age of onset and another for duration of illness. Duration was shorter for males, especially for those with an affected father.

Significant linkage disequilibrium between the Huntington disease gene and the loci D4S10 and D4S95 in the Dutch population.

Significant linkage disequilibrium has been found between the Huntington disease (HD) gene and DNA markers located around D4S95 and D4S98. The linkage-disequilibrium studies favor the proximal location of the HD gene, in contrast to the conflicting results of recombination analyses. We have analyzed 45 Dutch HD families with 19 DNA markers and have calculated the strength of linkage disequilibrium. Highly significant linkage disequilibrium has been detected with D4S95, consistent with the studies in other populations. In contrast with most other studies, however, the area of linkage disequilibrium extends from D4S10 proximally to D4S95, covering 1,100 kb. These results confirm that the HD gene most likely maps near D4S95.

DNA-testing for Huntington's disease in The Netherlands: a retrospective study on psychosocial effects.

Presymptomatic DNA-testing for Huntington's disease has made it possible to predict whether or not at-risk individuals are gene-carriers with a reliability of about 98%. In our retrospective study of 18 tested individuals, most of the newly identified carriers function apparently well. They use avoidance and repression of affect as psychological defense strategies. However, 8 out of 9 non-carriers do not experience the expected relief about their test results. They experience survivor guilt and emotional numbness and find it difficult to cope with the effects of the test results on the family system. The partners of gene-carriers are at risk of becoming emotionally isolated by putting aside their own feelings for fear of seeming self-centered. Appreciation of these effects on tested individuals is important and professional support is needed to prevent post-traumatic stress disorders. Whatever the test result may be, the working through process may take years rather than months. These findings have important implications for patient care and necessitate an extended period of observation after presymptomatic testing.

Age at onset in Huntington's disease: effect of line of inheritance and patient's sex.

The Leiden Roster for Huntington's disease (HD) contained data on 2617 cases up to July 1988. The age at onset (AO) was known in 1084 cases and in 1020 of these both their AO and the sex of the affected parent was known. The mean AO was higher for females than for males and higher for maternal than for paternal cases. However, in the group born before 1925 only females with maternal inheritance had a higher mean AO. Data on influence of sex and line of inheritance were present for the grandparents as well as for the great grandparents. Influence of the line of inheritance from the grandparents was particularly present for the grandmother-father (MP) lineage; regarding the great grandparents a significant difference was found between the MPM and PMP lineage. The results obtained for juvenile HD cases were comparable to those previously published. In late onset cases (over 50 years) no maternal preponderance in inheritance was found.

Presymptomatic, prenatal, and exclusion testing for Huntington disease using seven closely linked DNA markers.

Presymptomatic, testing, prenatal diagnosis, or exclusion testing are now available for persons at risk for Huntington disease. These tests will reduce uncertainty, assist in life planning, and prevent the birth of potentially affected children. We present the results of presymptomatic tests for 37 applicants including two prenatal and one exclusion test in 23 families. We initially used the markers G8, H5.52, F5.53, and pTV20 (D4S10), p8 (D4S62), and pRB1.6 (D4S81) and extended the informativity of the test at a later stage with the markers pKP1.65, C4H, S1.5 (D4S43), 674 (D4S95), 157.9 (D4S111), and YNZ32 (D4S125). Applicants with an unsuitable family structure were not admitted to the test. Of the 37 applicants, 33 were informative. In our hands the most efficient strategy is first to use the markers H5.52 (D4S10), pRB1.6 (D4S81), 674 (D4S95), pKP1.65 (D4S43), 157.9 (D4S111), YNZ32 (D4S125), and 252.3 (D4S115). The overall informativity in our data set was 84% and in the most recent test we achieved a 90-95% informativity. The other markers are used only when the first set is not informative.

Hereditary cerebral haemorrhage with amyloidosis--Dutch type. Magnetic resonance imaging findings in 7 cases.

The clinical history and magnetic resonance imaging (MRI) findings are presented of 7 patients with hereditary cerebral haemorrhage with amyloidosis--Dutch type (HCHWA-D). The diagnosis was based on clinical and genealogical data, was confirmed in 3 patients at autopsy and in 2 others by biopsy. Focal neurological signs, and at least some degree of global cognitive deterioration, were observed in all patients, with unequivocal dementia in 4. MRI showed haemorrhages and areas of gliosis and, to a variable extent, hyperintensity of the white matter in T2-weighted images. Neuropathological examination revealed a large recent haemorrhage together with residual lesions from previous haemorrhages or infarcts in all patients examined. The white matter lesions, present on MRI, turned out to be areas of 'incomplete infarction' with demyelination. It is concluded that (hereditary) amyloid angiopathy can lead to strokes, but also to subcortical ischaemic encephalopathy. Amyloid angiopathy should therefore be considered in the differential diagnosis of white matter lesions, found on CT or MRI, especially when patients present with a cerebral haemorrhage. The relationship between HCHWA-D and Alzheimer's disease, another disease with cerebral amyloid deposition and diffuse white matter involvement, is discussed.

Amyloid beta protein precursor gene and hereditary cerebral hemorrhage with amyloidosis (Dutch).

Human hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), an autosomal dominant form of cerebral amyloid angiopathy (CAA), is characterized by extensive amyloid deposition in the small leptomeningeal arteries and cortical arterioles, which lead to an early death of those afflicted in their fifth or sixth decade. Immunohistochemical and biochemical studies have indicated that the amyloid subunit in HCHWA-D is antigenically related to and homologous in sequence with the amyloid beta protein isolated from brains of patients with Alzheimer's disease and Down syndrome. The amyloid beta protein is encoded by the amyloid beta protein precursor (APP) gene located on chromosome 21. Restriction fragment length polymorphisms detected by the APP gene were used to examine whether this gene is a candidate for the genetic defect in HCHWA-D. The data indicate that the APP gene is tightly linked to HCHWA-D and therefore, in contrast to familial Alzheimer's disease, cannot be excluded as the site of mutation in HCHWA-D.