Supernumerary chromosome inherited from a maternal balanced translocation leading to pure trisomy 9p.

We describe a child with a supernumerary chromosome defined as der(9)t(9;22) (q12;p11), resulting in trisomy 9p and trisomy 22p. The mother carried the balanced translocation. In G- and C-banding the derivative chromosome 9 appeared to be dicentric and to contain 22q material. Using in situ hybridization we defined the exact breakpoints of the translocation and ruled out the possibility of a centric fission in the mother's chromosomes.

De novo dup(X)(q22.1q25) in a girl with an abnormal phenotype.

Duplication of a portion of Xq has been observed in males with abnormalities. In some cases, their mothers or even grandmothers had the same duplication but did not show any phenotypic abnormalities. However, a few cases of females with a de novo Xq duplication do present some abnormalities. We describe a 16-month-old girl with short stature, motor delay with hypotonia, scoliosis, right hemiatrophy, and ptosis of the right eye, with an Xq duplication. The duplicated region is read dir dup(X)(q22.1q25).

Club foot, an adverse outcome of early amniocentesis: disruption or deformation? CEMAT. Canadian Early and Mid-Trimester Amniocentesis Trial.

An association between the occurrence of club foot and early amniocentesis has been reported. The largest of these randomised studies was the Canadian Early and Mid-Trimester Amniocentesis Trial. Data describing the neonatal outcome, focusing on this association, are presented. Possible mechanisms for the association and the implications for the development of club foot are discussed.

Prevalence of congenital anomalies at birth among offspring of women at risk for a genetic disorder and with a normal second-trimester ultrasound.

The goal of this study was to determine the prevalence and the nature of congenital anomalies found at birth in offspring of women who had a normal second-trimester ultrasound and/or amniocentesis. Two groups of women were studied in our prenatal diagnosis clinic between 1991-1997. Group 1 consisted of pregnant women who had an amniocentesis for advanced maternal age (AMA), or for familial chromosomal or monogenic disorders. Group 2 consisted of pregnant women attending the prenatal diagnosis clinic and who had no indication for amniocentesis. Those with an abnormal ultrasound and/or amniocentesis were excluded. At the time of delivery, a questionnaire was sent pertaining to perinatal complications and the anomalies detected during the neonatal period. From a total of 15, 370 questionnaires sent from 1991-1997, 10,823 (group 1, n = 8,877; group 2, n = 1,946) were returned (overall response rate, 70.4%). Mean maternal age was 36 years in group 1 and 29 years in group 2. The prevalence of perinatal complications was similar in the two groups. In each group, the prevalence of all unforeseen anomalies was 2.9%. In group 1, the distribution of those anomalies was: major anomalies, 67.7%; minor anomalies, 23.9%; and multiple congenital anomalies (MCA), 8.3%. In group 2, the distribution was: major anomalies, 70.7%; minor anomalies, 24.1%; and MCA, 5.2%. In patients at risk for a genetic disease and consulting in a prenatal diagnosis clinic, the prevalence of all anomalies diagnosed at birth was 2.9%, even if the second-trimester ultrasound and amniocentesis results were normal. Therefore, it is important to inform those couples of this remaining risk.

Cytogenetic aspects of the Canadian early and mid-trimester amniotic fluid trial (CEMAT).

Cytogenetic results from a large multicentre randomized controlled study of 2108 amniotic fluids obtained at 11+0-12+6 weeks (EA) and 1999 fluids at 15+0-16+6 weeks (MA) were compared. There was no statistically significant difference in the rate of chromosome abnormalities (EA =1.9 per cent; MA=1.7 per cent) or level III mosaicism (EA=0.2 per cent; MA= 0.2 per cent) between the groups. Level I and Level II mosaicism occurred more frequently in MA. Maternal cell contamination was not significantly different between the groups, but maternal cells only were analysed from one bloody EA fluid. The number of repeat amniocenteses because of cytogenetic problems was 2.2 per cent in the EA group compared with only 0.3 per cent in the MA group. On average, culture of EA fluids required one day more than MA fluids. Although both culture success (97.7 per cent) and accuracy (99.8 per cent) were high for patients randomized to the EA group, routine amniocentesis prior to 13 weeks' gestation is not recommended for clinical reasons including an increased risk of fetal loss and talipes equinovarus.

Frequencies of chromosomal abnormalities at amniocentesis: over 20 years of cytogenetic analyses in one laboratory.

Prenatal diagnosis of chromosomal disorders has been performed for more than 20 years, mainly for advanced maternal age. Chromosomal abnormality rates derived from second trimester amniocentesis have mainly come from a collection of small-scale studies from North America and Western Europe. Accurate risk estimates for chromosomal abnormalities are important tools for the physician or obstetrician who would need to make referrals to a prenatal genetic center. This paper presents amniocentesis rates of clinically significant cytogenetic abnormalities for various indications, including advanced maternal age, previous chromosomal abnormality, parental structural rearrangement and a family history of aneuploidy as defined in the text. These data come from a Canadian prenatal diagnosis laboratory with more than 20 years experience in second trimester cytogenetic analysis. They show that the overall frequency of chromosomal abnormalities for advanced maternal age (> or = 35 years) is 1.79%. In this group, 21% of all abnormalities are structural rearrangements (including markers) and less than half of all abnormalities are trisomy 21. The advanced maternal age specific risk of aneuploidies at second trimester is 1.24%. Recurrence risk for aneuploidy after a previous one is 1.29%. However, it is much higher (4.84%) for women of > or = 35 years. When a parent's brother, sister, nephew or niece is affected, the risk of occurrence of aneuploidies (0.24%) is not elevated. When there is a balanced translocation in one of the parents, the overall risk is 10.2% for unbalanced translocations and 37.3% for balanced translocations.

Monozygotic twins with 45,X/46,XY mosaicism discordant for phenotypic sex.

We report on two sets of monozygotic twins (MZTs) discordant for phenotypic sex ascertained at birth when the female twin was noted to have signs of the Ullrich-Turner syndrome. Cytogenetic investigations on the female of the first pair showed 45,X/46,XY mosaicism in lymphocytes but fibroblasts grown from two skin biopsies at separate sites and from gonadal tissue showed only 45,X cells. The male showed mosaicism in both blood lymphocytes and skin fibroblasts. In the second family, both twins also showed mosaicism in lymphocytes. The female had a 45,X karyotype in fibroblasts from skin and gonadal tissue, but in contrast to the first family, the male twin had a normal male karyotype in fibroblasts from skin biopsy and from connective tissue adjacent to the vas deferens. Discordant phenotypic sex in monozygotic twins is rare. As in our cases, the nine previously reported sets of MZTs all had mosaicism for sex chromosome abnormalities. A mitotic error leading to the loss of a Y chromosome prior to, accompanying, or following the twinning process would account for the reported combinations of karyotypes.

Cloning, expression and chromosomal mapping of human lysosomal sialidase and characterization of mutations in sialidosis.

Sialidase (neuraminidase, EC 3.2.1.18) catalyses the hydrolysis of terminal sialic acid residues of glyconjugates. Sialidase has been well studied in viruses and bacteria where it destroys the sialic acid-containing receptors at the surface of host cells, and mobilizes bacterial nutrients. In mammals, three types of sialidases, lysosomal, plasma membrane and cytosolic, have been described. For lysosomal sialidase in humans, the primary genetic deficiency results in an autosomal recessive disease, sialidosis, associated with tissue accumulation and urinary excretion of sialylated oligosaccharides and glycolipids. Sialidosis includes two main clinical variants: late-onset, sialidosis type I, characterized by bilateral macular cherry-red spots and myoclonus, and infantile-onset, sialidosis type II, characterized by skeletal dysplasia, mental retardation and hepatosplenomegaly. We report the identification of human lysosomal sialidase cDNA, its cloning, sequencing and expression. Examination of six sialidosis patients revealed three mutations, one frameshift insertion and two missense. We mapped the lysosomal sialidase gene to human chromosome 6 (6p21.3), which is consistent with the previous chromosomal assignment of this gene in proximity to the HLA locus.

Age-specific distribution of plasma amino acid concentrations in a healthy pediatric population.

Reference values were determined for 23 plasma free amino acids from measurements done in 148 healthy children ranging from 0 to 18 years of age. Amino acid analysis was performed by ion-exchange chromatography. We propose a graphic form of presenting the age-specific distribution of plasma amino acid concentrations where the 10th, 50th, and 90th quantiles are illustrated. Although each amino acid possesses its own pattern of distribution, we can identify five different profiles. Nine amino acids (alanine, arginine, asparagine, methionine, ornithine, phenylalanine, proline, threonine, and tyrosine) demonstrate a decrease in their concentrations during the first year of life; their concentrations then tend to increase throughout childhood and adolescence. Nine others (cystine, glutamine, glycine, histidine, isoleucine, leucine, lysine, tryptophan, and valine) show a steady increase throughout infancy, childhood, and adolescence. Five amino acids (aspartic acid, citrulline, glutamic acid, serine, and taurine) do not follow these two common profiles. For the first time, quantile curves are produced to illustrate the age-dependent variation of amino acid concentrations from infancy to adulthood. This alternative way of presenting amino acid concentrations may facilitate the follow-up of patients with inborn errors of amino acid metabolism.

Fragile site and interstitial telomere repeat sequences at the fusion point of a de novo (Y;13) translocation.

We describe a novel fragile site in a rearranged chromosome, associated with the presence of telomeric repeat sequences at the fusion point of a translocation between chromosomes 13 and Y. The case reported in this study shows a de novo (Y;13) translocation, which appears to represent fusion of an apparently intact chromosome Y with a chromosome 13 that has lost only part of its short arm. Ten percent of the cells show a normal karyotype without the (Y;13) translocation. Molecular cytogenetic studies of the derived Y;13 chromosome revealed three hybridization sites of the telomeric probes-one at each end and one at the breakpoint junction. A fragile site is also observed in the intrachromosomic telomeric region. This coincidence suggests that the telomere repeat sequences (TTAGGG)n, when present at an interstitial chromosomal location, can promote the formation of a novel fragile site.

Fetal congenital diaphragmatic hernia: accuracy of sonography in the diagnosis and prediction of the outcome after birth.

OBJECTIVE: This study evaluated the diagnostic accuracy of prenatal sonography in congenital diaphragmatic hernia (CDH) and assessed sonographic predictors of postnatal outcome. MATERIALS AND METHODS: Sonograms and medical records of 43 fetuses with CDH were retrospectively reviewed. Sonographic features were correlated to clinical evolution and surgical and pathologic findings. RESULTS: CDH was diagnosed prenatally with sonography in 40 cases. Intrathoracic stomach and liver were routinely identified. Ipsilateral lung tissue could not be differentiated from herniated content. Contralateral lung was identified in all cases except two. The overall survival rate was 43% after excluding terminated pregnancies. Besides associated malformations and chromosomal anomalies, the only statistically significant predictor of survival was the quantification of the contralateral lung area at the level of an axial four-chamber view: The survival rate was 86% when the contralateral lung area was equal to or greater than one half the area of the hemithorax. CONCLUSION: Sonography is highly accurate for prenatal diagnosis od CDH. Sonography also assists the prognostication of postnatal outcome in isolated CDH by allowing quantification of the contralateral lung area on a four-chamber view.

Germinal HPRT splice donor site mutation results in multiple RNA splicing products in T-lymphocyte cultures.

We have used peripheral blood T-lymphocyte cultures to analyze the hprt mutation in two Lesch-Nyhan syndrome males who are cousins and to confirm the carrier status of female members of the family. Both cDNA and genomic DNA sequencing studies show that this patient carries a hitherto undescribed single base deletion in the exon 5 donor splice site sequence (I5: +1, delta G, base number 31635). The largest cDNA product contained all nine hprt exons plus an insertion of 66 bases of intron 5, consistent with the use of a cryptic splice site in intron 5 (aag67/gtaagc). This splicing error would result in a chain terminating codon immediately after exon 5 (I5:2-4, taa) and predicts a polypeptide of 133 amino acids. This loss of the normal splice donor site also results in multiple hprt mRNA species, combining the use of the cryptic splice site in intron 5 and splicing errors involving exons 2-6. In addition to defining a new Lesch-Nyhan mutation (hprtHenryville), these results provide insight into aberrant splicing of hprt mRNA in T-lymphocytes.

Chronic sodium benzoate therapy in children with inborn errors of urea synthesis: effect on carnitine metabolism and ammonia nitrogen removal.

Sodium benzoate (SB) therapy is known to increase ammonia (NH3) nitrogen elimination via conjugation with glycine and excretion as urinary hippurate. In 16 children with inborn errors of urea synthesis we studied two issues: (1) the effect of chronic SB administration upon carnitine metabolism and (2) the efficacy of chronic SB therapy as measured by the molar ratio of hippurate excretion to SB intake. Measurements were performed during elective hospitalizations when the patients were in stable metabolic condition. We found that chronic SB therapy is not associated with a constant level of hippurate elimination and that interindividual and intraindividual variability may result in irregular removal of NH3 nitrogen. This variability may be due to various factors including the formation of small quantities of benzoylcarnitine, which was detected in the plasma of three of four patients receiving SB and carnitine therapy and in one of two patients on SB therapy without carnitine supplementation. The ratios of acyl to free carnitine were elevated in both plasma and urine in patients not receiving carnitine supplementation, but were normal in patients receiving supplementation.

Prenatal diagnosis of Smith-Lemli-Opitz syndrome is possible by measurement of 7-dehydrocholesterol in amniotic fluid.

Amniocentesis was performed at 17.3 weeks in a pregnancy with severe intrauterine growth retardation. Cytogenetic studies on amniocytes were normal, 46,XX, and the pregnancy was continued. The diagnosis of Smith-Lemli-Opitz syndrome was suspected in the neonatal period and confirmed by the presence of 7-dehydrocholesterol (7-DHC) in the plasma (0.4 mmol/l, normal = not detectable) associated with a low total cholesterol concentration (0.4 mmol/l, normal = 2.56 +/- 0.23). Retrospective analysis of the amniotic fluid sample revealed an elevated level of 7-DHC (0.022 mmol/l; normal = undetectable). Therefore measurement of 7-DHC levels in amniotic fluid during the second trimester of pregnancy is useful for the prenatal diagnosis of Smith-Lemli-Opitz syndrome in families at risk and should be considered in cases of severe growth retardation of unknown aetiology for which amniotic fluid is available and in which a normal chromosomal pattern in amniocytes is present.

Molecular prenatal diagnosis of 3-hydroxy-3-methylglutaryl CoA lyase deficiency.

We report the first molecular prenatal diagnosis of 3-hydroxy-3-methylglutaryl CoA lyase (HL) deficiency. The proband had a classic but severe presentation with hypoketotic hypoglycaemia and acidosis, secondary mental retardation, and epilepsy, and HL deficiency was documented in cultured fibroblasts. We found him to be homozygous for the frameshift mutation N46fs (+1), which yields a distinct pattern on single-strand conformation polymorphism (SSCP) analysis. In two subsequent pregnancies, molecular prenatal diagnosis was performed using SSCP. In the first, chorionic villus biopsy was normal. In the second pregnancy, amniocentesis revealed an affected fetus. In both pregnancies, the diagnosis was confirmed enzymatically. HL activity was less than 7 per cent of control values in amniocytes and fetal liver of the affected pregnancy. In the second pregnancy, amniotic fluid metabolite measurements by stable isotope dilution-selected ion monitoring mass spectrometry showed greater than 100-fold increases of 3-hydroxy-3-methylglutaric acid and of 3-methylglutaconic acid levels compared with controls.

Parental reaction and adaptability to the prenatal diagnosis of fetal defect or genetic disease leading to pregnancy interruption.

The objective of the study was to evaluate the psychological reaction of two groups of parents to a pregnancy termination after they had undergone a prenatal diagnostic procedure. The analysis involved interviews with a study group of 76 patients who were at risk of giving birth to a child with a genetic disease or defect and a comparison group of 124 who had a pregnancy termination after a major anomaly had been detected by routine ultrasound and who were not at known risk for a genetic disease. Only patients in the study group had received counselling before the prenatal diagnosis and were aware that the fetus could be affected. The overall reaction of the comparison group was one of shock, denial of fetal abnormality, and guilt over 'abandoning the fetus'. A feeling of guilt was expressed by patients in the comparison group (73 per cent versus 29 per cent) in the period immediately following the interruption. One-third of patients in both groups felt obliged to undergo a therapeutic abortion. More patients in the study group than in the comparison group expressed the need to see a psychiatrist at the time of the study (19 per cent versus 7 per cent) and viewed future pregnancies as a replacement for the lost pregnancy (63 per cent versus 19 per cent). The recommendations of the study focus on information sessions to personnel, nursing support, analgesia during the expulsion period, an atmosphere of respect that should be present at the time that the fetus is viewed, the anticipation of mourning, and the long-term follow-up of the couple to ensure that counselling for future pregnancies and psychological support are provided when needed.

New autosomal recessive form of amelia.

Amelia is a rare, usually sporadic malformation. We report on a family in which three fetuses had amelia of the upper limbs and variable deficiency of the lower limbs. The fetuses also had minor facial anomalies. Recurrence of the condition in sibs of both sexes suggests autosomal recessive inheritance. Recurrent amelia has been documented in only a few families most often associated with a different set of malformations. Possibly, mutations in more than one gene with different modes of transmission can lead to this severe limb deficiency. We speculate that the mutation found in our cases interferes with formation of the apical ectodermal ridge in the upper limbs and results in its premature degeneration in the lower limbs.

Selective abortion: a new moral order? Consensus and debate in the medical community.

The authors discuss the results of a survey of the attitudes of Canadian and French (Picardie, Nord-Pas de Calais) physicians toward selective abortion of fetal anomalies detected by ultrasound, amniocentesis, or chorionic villus sampling. The study documents the threshold of acceptability of abortion of fetuses with selected anomalies, as well as the physicians' own perceptions of their role in the decision to abort. While there was no consensus among all Canadian physicians regarding the acceptability of abortion, more than 55 percent from France and Quebec would accept selective abortion of a fetus affected with trisomy 21, Duchenne muscular dystrophy, cystic fibrosis, Huntington's chorea, or spina bifida. In the province of Quebec, Anglophone physicians showed a greater acceptance of abortion than did their French-speaking colleagues. In reference to the physician's role in the decision to abort, French physicians are more directive than North American physicians. Cultural predispositions may explain these differences in attitudes.

PIP: Medical genetics is currently at the center of social debate on the future of human reproduction. Given the current availability of quite a few prenatal diagnostic tools capable of detecting pathologies in utero, the authors investigated the attitudes of selected French and Canadian physicians toward selective abortion following the detection of fetal anomalies by ultrasound, amniocentesis, or chorionic villus sampling. The study was first carried out in the province of Quebec and the Picardie and Nord-Pas de Calais regions of France, while a second study was conducted in Anglophone Canada within the framework of a royal commission. In all of Canada, 3072 physicians returned completed questionnaires for a response rate of 52%. 588 physicians in France returned the questionnaire for a response rate of 54%. There was no consensus among Canadian physicians on the acceptability of abortion, but more than 55% of respondents from France and Quebec would accept the selective abortion of a fetus affected with trisomy 21, Duchenne muscular dystrophy, cystic fibrosis, Huntington's chorea, or spina bifida. In the province of Quebec, Anglophone physicians were more accepting of abortion than their Francophone colleagues. Regarding the physician's role in the decision to abort, French physicians are more directive than North American physicians. Cultural predispositions may explain these differences in attitude.

Autosomal dominant polycystic kidney disease in the fetus.

We report on 3 cases with a fetal presentation of autosomal dominant polycystic kidney disease (ADPKD), which illustrate the variable expression of ADPKD during fetal life. Fetus 1 was diagnosed at 20 weeks of gestation by ultrasonography; a molecular prenatal diagnosis was performed at 10 weeks on fetus 2, a sib of fetus 1; and ADPKD was an incidental finding in fetus 3 who was aborted at 16 weeks for anencephaly. All pregnancies were terminated and pathologic studies of the fetal kidneys were performed. From these cases and a review of the literature, we draw the following conclusions: (1) so far, all fetal ADPKD kidneys that have been histologically studied have shown cystic dilatations; 28/32 of these fetuses had ultrasonographic manifestations of the disease and/or had sibs with an early-onset form of it; (2) these cysts can be found in newly formed nephrons (fetus 2), predominantly in the more mature nephrons of the deep cortex (fetus 1) or more sparsely distributed in the cortex (fetus 3); these different patterns may reflect different rates of progression of the disease; (3) in contrast to the histologic findings in adult kidneys, glomeruli seem to be predominantly affected in fetal ADPKD; (4) severe fetal expression of ADPKD seems to cluster in some families; and (5) so far, all DNA analyses performed in families with subjects presenting during the fetal or neonatal period have been consistent with linkage to the PKD1 locus.

Recommendations on the use of folic acid supplementation to prevent the recurrence of neural tube defects. Clinical Teratology Committee, Canadian College of Medical Geneticists.

OBJECTIVE: To prevent the recurrence of neural tube defects (NTDs) in families at increased risk of having offspring with NTDs with the use of periconceptional folic acid supplementation. OPTIONS: Genetic counselling and prenatal diagnosis of NTDs. OUTCOMES: NTDs cause stillbirth, neonatal death and severe disabilities. The cost for medical care and rehabilitation in the first 10 years of life of a child with spina bifida cystica was estimated to be $42,507 in 1987. EVIDENCE: The authors reviewed the medical literature, communicated with investigators from key studies, reviewed policy recommendations from other organizations and drew on their own expertise. A recent multicentre randomized controlled trial showed that among women at high risk of having a child with an NTD those who received 4 mg/d of folic acid had 72% fewer cases of NTD-affected offspring than nonsupplemented women. Two previous intervention studies also demonstrated that folic acid supplementation was effective in reducing the rate of NTD recurrence. Several retrospective studies support this conclusion. VALUES: Recommendations are the consensus of the Clinical Teratology Committee of the Canadian College of Medical Geneticists (CCMG) and have been approved by the CCMG Board. The committee believes that primary prevention of NTDs is preferable to treatment or to prenatal detection and abortion. BENEFITS, HARMS AND COSTS: Folic acid supplementation should result in fewer NTDs among infants in Canada and ancillary savings in medical costs. The recommended dosage of folic acid is not known to be associated with adverse effects. Higher dosages of folic acid may make vitamin B12 deficiency difficult to diagnose and may alter seizure frequency in patients with epilepsy due to drug interactions with anticonvulsants. RECOMMENDATIONS: A minimum dosage of folic acid of 0.8 mg/d, not to exceed 5.0 mg/d, is recommended along with a well-balanced, nutritious diet for all women who are at increased risk of having offspring with NTDs and who are planning a pregnancy or may become pregnant. Supplementation should begin before conception and continue for at least 10 to 12 weeks of pregnancy. VALIDATION: These guidelines are similar to those of the Society of Obstetricians and Gynaecologists of Canada, the US Centers for Disease Control and Prevention and the Department of Health in Britain. SPONSORS: These guidelines were developed by the CCMG Clinical Teratology Committee and endorsed by the Board of the CCMG. No funding for the development of these guidelines was obtained from any other sources.