Mutation screening in British 21-hydroxylase deficiency families and development of novel microsatellite based approaches to prenatal diagnosis. (1/2367)

21-hydroxylase deficiency is a recessively inherited disorder of steroidogenesis, resulting from mutations in the CYP21 gene. This 3.5 kb gene and a highly related CYP21P pseudogene reside on tandemly duplicated 30 kb segments of DNA in the class III HLA region, and the great majority of pathogenic mutations result from sequence exchanges involving the duplicated units. We now describe a comprehensive survey of CYP21 mutations in the British population, encompassing a screen for 17 different mutations in a total of 284 disease chromosomes. The most common mutations were as follows: large scale deletions/conversions (45% of the affected chromosomes), the intron 2 splice mutation (30.3%), R357W (9.8%), and I172N (7.0%). Mutations were detected in over 92% of the chromosomes examined, suggesting that accurate DNA based diagnosis is possible in most cases using the described strategy. In order to extend highly accurate prenatal diagnosis to all families where samples are available from a previously affected child, we have developed a linkage analysis approach using novel, highly informative microsatellite markers from the class III HLA region.  (+info)

Variations in genetic assessment and recurrence risks quoted for childhood deafness: a survey of clinical geneticists. (2/2367)

We report here the results of a questionnaire survey of consultant clinical geneticists in the United Kingdom to which we had an 81% response rate. In this questionnaire we asked about: (1) the nature of services currently offered to families with hearing impaired children, (2) what recurrence risks they quoted in isolated non-syndromic cases, and (3) what they might suggest for improving the range of genetic services available at present. We noted great variation both in these services and in the recurrence risks quoted in isolated cases. Based on the results of the questionnaire, we have proposed a protocol for the investigation of permanent childhood hearing impairment, which we believe to be both comprehensive and practical in an outpatient clinic setting. It is only by improving existing clinical and social understanding and knowledge of childhood hearing impairment that it will become possible to use recent molecular advances to develop comprehensive and consistent services for these families.  (+info)

Dilemmas in counselling females with the fragile X syndrome. (3/2367)

The dilemmas in counselling a mildly retarded female with the fragile X syndrome and her retarded partner are presented. The fragile X syndrome is an X linked mental retardation disorder that affects males and, often less severely, females. Affected females have an increased risk of having affected offspring. The counselling of this couple was complicated by their impaired comprehension which subsequently impaired their thinking on the different options. The woman became pregnant and underwent CVS, which showed an affected male fetus. The pregnancy was terminated. Whether nondirective counselling for this couple was the appropriate method is discussed and the importance of a system oriented approach, through involving relatives, is stressed.  (+info)

Prenatal features of ductus arteriosus constriction and restrictive foramen ovale in d-transposition of the great arteries. (4/2367)

BACKGROUND: Although most neonates with d-transposition of the great arteries (TGA) have an uncomplicated preoperative course, some with a restrictive foramen ovale (FO), ductus arteriosus (DA) constriction, or pulmonary hypertension may be severely hypoxemic and even die shortly after birth. Our goal was to determine whether prenatal echocardiography can identify these high-risk fetuses with TGA. METHODS AND RESULTS: We reviewed the prenatal and postnatal echocardiograms and outcomes of 16 fetuses with TGA/intact ventricular septum or small ventricular septal defect. Of the 16 fetuses, 6 prenatally had an abnormal FO (fixed position, flat, and/or redundant septum primum). Five of the 6 had restrictive FO at birth. Five fetuses had DA narrowing at the pulmonary artery end in utero, and 6 had a small DA (diameter z score of <-2.0). Of 4 fetuses with the most diminutive DA, 2 also had an abnormal appearance of the FO, and both died immediately after birth. One other fetus had persistent pulmonary hypertension. Eight fetuses had abnormal Doppler flow pattern in the DA (continuous high-velocity flow, n=1; retrograde diastolic flow, n=7). CONCLUSIONS: Abnormal features of the FO, DA, or both are present in fetuses with TGA at high risk for postnatal hypoxemia. These features may result from the abnormal intrauterine hemodynamics in TGA. A combination of restrictive FO and DA constriction in TGA may be associated with early neonatal death.  (+info)

Recurrence of Marfan syndrome as a result of parental germ-line mosaicism for an FBN1 mutation. (5/2367)

Mutations in the FBN1 gene cause Marfan syndrome (MFS), a dominantly inherited connective tissue disease. Almost all the identified FBN1mutations have been family specific, and the rate of new mutations is high. We report here a de novo FBN1mutation that was identified in two sisters with MFS born to clinically unaffected parents. The paternity and maternity were unequivocally confirmed by genotyping. Although one of the parents had to be an obligatory carrier for the mutation, we could not detect the mutation in the leukocyte DNA of either parent. To identify which parent was a mosaic for the mutation we analyzed several tissues from both parents, with a quantitative and sensitive solid-phase minisequencing method. The mutation was not, however, detectable in any of the analyzed tissues. Although the mutation could not be identified in a sperm sample from the father or in samples of multiple tissue from the mother, we concluded that the mother was the likely mosaic parent and that the mutation must have occurred during the early development of her germ-line cells. Mosaicism confined to germ-line cells has rarely been reported, and this report of mosaicism for the FBN1 mutation in MFS represents an important case, in light of the evaluation of the recurrence risk in genetic counseling of families with MFS.  (+info)

Subfertile men with constitutive chromosome abnormalities do not necessarily refrain from intracytoplasmic sperm injection treatment: a follow-up study on 75 Dutch patients. (6/2367)

A follow-up study was performed to investigate the impact of the detection of a chromosome abnormality in infertile men who are candidates for intracytoplasmic sperm injection (ICSI) treatment. In this collaborative study between clinical genetics centres and fertility clinics in the Netherlands, 75 ICSI couples of which the male partners had a chromosome abnormality were included. All couples were extensively counselled on the risk of having a chromosomally unbalanced child. Forty-two out of 75 couples chose to proceed with the ICSI treatment. So far, treatment has resulted in a pregnancy in 11 cases. Four of them opted to have invasive prenatal diagnosis. Despite the genetic risks related to a chromosome abnormality in infertile men, a small majority (56%) of the couples did not refrain from the ICSI treatment.  (+info)

Lack of knowledge in health professionals: a barrier to providing information to patients? (7/2367)

OBJECTIVE: To assess obstetricians' and midwives' knowledge of routine prenatal screening tests for fetal abnormality and factors associated with such knowledge. DESIGN: Questionnaire assessment of antenatal clinic staff. SETTING: Six hospitals within the United Kingdom (four district general hospitals in London, one district general hospital in Wales, and one teaching hospital in Wales), offering routine prenatal screening tests. SUBJECTS: 29 obstetricians and 97 midwives were invited to participate, of whom 21 and 70 respectively responded to the questionnaire. MAIN MEASURES: Knowledge of prenatal tests, according to 19 item multiple choice questionnaire, reluctance to disclose uncertainty, and clinical experience. RESULTS: The overall response rate was 72% (91/126). In all, 43% of midwives and 14% of obstetricians obtained correct responses on fewer than half the items. Reluctance to disclose uncertainty to patients was associated in obstetricians with having less knowledge about prenatal testing (r = -0.50; p < 0.025, Pearson product moment correlation) and in midwives with more clinical experience (r = 0.43; p < 0.001). CONCLUSIONS: Lack of knowledge and greater clinical experience seem to be important barriers to providing patients with information about prenatal screening tests.  (+info)

Feasibility and acceptance of screening for fragile X mutations in low-risk pregnancies. (8/2367)

Fragile X syndrome is the second leading cause of mental retardation after Down syndrome. Most women carriers of the fragile X mutation are unaware of their condition. We critically evaluated whether screening pregnant women at low risk for FMR1 mutation would be feasible as a routine part of antenatal care in general practice. We also studied acceptance and attitudes to gene testing. From July 1995 until December 1996, a carrier test was offered at the Kuopio City Health Centre free of charge to all pregnant women in the first trimester following counselling given by midwives on fragile X syndrome. All women found to be carriers of FMR1 gene mutations underwent detailed genetic counselling and were offered prenatal testing. Attitudes towards the gene test were elicited by questionnaire. Most pregnant women (85%) elected to undertake the gene test. Six women were found to be carriers (a rate of 1 in 246), and all subsequently accepted prenatal testing. Three foetuses had a normal FMR1 gene, one had a large premutation, one a 'size mosaic' mutation pattern, and another a full mutation. This observational and interventional study demonstrates that antenatal screening provides an effective way of identifying carriers and incorporating prenatal testing into this process.  (+info)

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