Progressive osseous heteroplasia: a model for the imprinting effects of GNAS inactivating mutations in humans.

CONTEXT: Heterozygous GNAS inactivating mutations are known to induce pseudohypoparathyroidism type 1a when maternally inherited and pseudopseudohypoparathyroidism when paternally inherited. Progressive osseous heteroplasia (POH) is a rare disease of ectopic bone formation, and studies in different families have shown that POH is also caused by paternally inherited GNAS mutations. OBJECTIVE: Our purpose was to characterize parental origin of the mutated allele in de novo cases of POH and to draw phenotype/genotype correlations according to maternal or paternal transmission of a same GNAS mutation. DESIGN AND SETTING: We conducted a retrospective study on patients addressed to our referral center for the rare diseases of calcium and phosphorus metabolism. PATIENTS AND METHODS: We matched 10 cases of POH with cases of pseudohypoparathyroidism type 1a carrying the same GNAS mutations. MAIN OUTCOME MEASURES: The parental origin of the mutated allele was studied using informative intragenic polymorphisms and subcloning of PCR products. RESULTS: Paternal origin of GNAS mutations was clearly demonstrated in eight POH cases including one patient with mutation in exon 1. Genotype/phenotype analyses suggest that there is no direct correlation between the ossifying process and the position of the inactivating GNAS mutation. It is, however, more severe in patients in whom origin of the mutation is paternal. Severe intrauterine growth retardation was clearly evidenced in paternally inherited mutations. CONCLUSIONS: Clinical heterogeneity makes genetic counseling a delicate matter, especially in which paternal inheritance is concerned because it can lead to either a mild expression of pseudopseudohypoparathyroidism or a severe expression of POH.

Screening of SLC26A4 (PDS) gene in Pendred's syndrome: a large spectrum of mutations in France and phenotypic heterogeneity.

Sensorineural hearing defect and goiter are common features of Pendred's syndrome. The clinical diagnosis of Pendred's syndrome remains difficult because of the lack of sensitivity and specificity of the thyroid signs. The identification of PDS as the causative gene allowed molecular screening and enabled a re-evaluation of the syndrome to identify potential diagnostic characteristics. This report presents the clinical and genotypic findings of 30 French families, for whom a diagnosis of Pendred's syndrome had been made. Twenty-seven families had at least one mutated allele. Twenty-eight different mutations were identified, 11 of which had never been previously reported. The main clinical characteristics were: early hearing loss, fluctuation in terms of during deafness evolution, and the presence of an enlarged vestibular aqueduct.

Neonatal screening for cystic fibrosis in Brittany, France: assessment of 10 years' experience and impact on prenatal diagnosis.

BACKGROUND: Neonatal screening for cystic fibrosis has been a subject of debate over the past few years. This study assesses 10 years of neonatal screening in Brittany, France, and examines its impact on prenatal screening of subsequent pregnancies in couples with an affected child. METHODS: The study included all the neonates screened for cystic fibrosis in Brittany from Jan 1, 1989, to Dec 31, 1998. The screening consisted of an immunoreactive trypsinogen assay from dried blood spots, plus, from 1993, mutation analysis. Data were collected on incidence of cystic fibrosis, and genotypic and biochemical characteristics. The use of prenatal screening of subsequent pregnancies in affected families was also investigated. FINDINGS: Of the 343,756 neonates screened, 118 children with cystic fibrosis were identified, giving an incidence of one in 2913. All mutated alleles were characterised: 34 different mutations resulting in 36 genotypes were detected. The introduction of DNA analysis into the protocol greatly reduced the recall rate and increased the sensitivity of the test. The mean cost of the screening programme was US$2.32 per screened child. 39 (34%) of the families identified by neonatal screening opted for subsequent prenatal diagnosis at least once. 12 couples would have benefited from this procedure while their first child was still symptom-free. 42 healthy children were born, and 18 pregnancies were terminated (therapeutic abortion rate of 100%). INTERPRETATION: We have shown the feasibility of neonatal screening for cystic fibrosis in Brittany. Through the detection of a large range of mutations, neonatal screening provides the opportunity for more reliable prenatal diagnosis and cascade screening. The neonatal screening programme described here could provide a good model for other countries intending to initiate such a scheme.

Fronto-otopalatodigital osteodysplasia: clinical evidence for a single entity encompassing Melnick-Needles syndrome, otopalatodigital syndrome types 1 and 2, and frontometaphyseal dysplasia.

Otopalatodigital syndrome type 2 is an X-linked disorder with minimal expression in carrier females and comprises typical facial anomalies and a generalized bone dysplasia with osteodysplastic changes, brachydactyly, and impaired survival. Recently several other severe malformations were reported in the condition. Melnick-Needles syndrome is an X-linked dominant disorder. Affected males are usually sporadic cases. The exceptional males born to symptomatic women present with a lethal disorder comprising generalized osteodysplasia, deficiency of the first ray, and facial anomalies strikingly similar to those of otopalatodigital syndrome type 2. We report here on three boys with classical, severe, and lethal otopalatodigital type 2 syndrome, and three boys with severe (lethal) Melnick-Needles syndrome, born to affected mothers. We suggest that otopalatodigital type 1 and 2, Melnick-Needles syndrome and frontometaphyseal dysplasia, sharing many clinical manifestations and a similar mode of inheritance, are variants of the same condition: fronto-otopalatodigital osteodysplasia. The relationships to similar syndromes (i.e., Saint-Martin-Gardner-Morrisson syndrome, serpentine fibula syndrome, atelosteogenesis type 3, boomerang dysplasia, and Yunis-Varon syndrome) are discussed.

Neonatal screening for cystic fibrosis: result of a pilot study using both immunoreactive trypsinogen and cystic fibrosis gene mutation analyses.

We have evaluated a two-tier neonatal cystic fibrosis (CF) screening of immunoreactive trypsinogen (IRT) followed by CFTR gene mutation analysis using a systematic scanning of exons 7, 10, and 11, and, if necessary, by direct DNA sequencing. Over an 18-month period we screened 32,300 neonates born in the western part of Britanny. The first tier, involving IRT screening at 3 days of age, utilizes a low elevation of the trypsinogen level (600 ng/ml), which is highly sensitive. The second tier, which corresponds to the exhaustive screening for mutations in three exons of the gene, is highly specific for this population (Britanny). The false positive rate is very low, and no false negatives have been reported to date. This strategy has allowed the identification of five novel alleles (V322A, V317A, 1806 del A, R553G, G544S).

[Reflections on 10 years of medically induced abortions in Ille-et-Vilaine]. / Réflexions sur 10 ans d'interruptions médicales de grossesse (IMG) en Ille-et-Vilaine.

The medical files of 532 patients who underwent medically induced abortion over a 10-year period (1982-1991) in the French department of Ille-et-Vilaine were studied in order to evaluate the indications and outcomes. Among the patients, 358 resided in the department (67%). Comparatively with the number of births during the 10-year period, there was a relative increase in the number of medically induced abortions from 3.5/1000 to 5.5/1000. This parameter was taken into consideration for the interpretation of a parallel decrease in the perinatal mortality during the same period, from 5.9/1000 to 5.1/1000. There was a maternal indication in 91 cases which correspond to the former category of therapeutic induced abortions. There was a clear increase in 1991 corresponding to abortions induced because of extremely premature rupture of the membranes which were formerly allowed to continue to dead births. Foetal indications were frequent: 441 cases (83%). Exogenous causes were lower (15.6%), particularly due to the disappearance of indications resulting from maternal irradiation. For indications related to infection, the vaccination against rubella and improved prenatal diagnosis resulted in the disappearance of rubella as an indication during the last three years of the study and a clear decrease in the number of toxoplasmosis indications. There were few indications due to maternal infection by human immunodeficiency virus (4 cases). Chromosomal abnormalities were the main cause of medically induced abortion among the foetal indications (27.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of 160 CF chromosomes: detection of a novel mutation in exon 20.

The cystic fibrosis (CF) gene has been cloned and a major mutation identified (delta F508). This 3-bp deletion has been found in approximately 70% of CF chromosomes. We have used the strategy of denaturing gradient gel electrophoresis followed by direct sequencing of the polymerase chain reaction products, in order to detect other mutations in exons 10, 11 and 20 of the CF transmembrane conductance regulator gene. A new mutation, F1286-S, was found in exon 20. It involves a nucleotide change of T-->C at nucleotide 3989 and changes a phenylalanine into serine at position 1286 of the protein.

[An example of detection of heterozygotes and antenatal diagnosis in four families with anhidrotic ectodermal dysplasia]. / Un exemple de diagnostic d'hétérozygotes et de diagnostic anténatal dans quatre familles de dysplasie ectodermique anhidrotique.

Anhidrotic ectodermal dysplasia is an X-linked inherited skin disorder; only affected males exhibit the complete syndrome, whereas females may have a few mild features. The gene involved in this disease is located in the proximal area of the long arm of the X chromosome, in the q13 position. Molecular analysis is very helpful for calculating the risk of transmission in sisters with normal phenotypes and affected individuals (family 1 provides an example), but cannot solve all problems (example of family 4). The best results are obtained when there are two informative markers, each located on either side of and very close to the mutant gene. Molecular analysis can also be applied to chorionic villi sampled at the tenth week of gestation in order to achieve antenatal diagnosis in male fetuses in high risk families. Until recently, antenatal diagnosis could be performed only at the twentieth week of gestation by the demonstration of inadequate development of skin glands in skin biopsy specimens sampled under fetoscopy. Family 2 provides an example of antenatal diagnosis and highlights the risk of error that always exists in molecular analysis studies.

Unexpected ultrasonographic prenatal diagnosis of autosomal dominant polycystic kidney disease.

The prenatal diagnosis of autosomal dominant polycystic kidney disease (ADPKD) is now being reported with increasing frequency. We report three cases and review 12 cases of ADPKD diagnosed in the fetus by ultrasonographic findings. Increased echogenicity and renal enlargement are the main ultrasonographic signs of ADPKD. Renal cysts are uncommon. Diagnosis is easy in a family with a positive ADPKD history. Conversely, there may be no apparent family history, as in our three cases and three cases from the literature. We consider the problems of unexpected diagnosis, family investigation, and the prognosis of ADPKD in children with prenatally diagnosable forms.

Molecular definition of the 11p15.5 region involved in Beckwith-Wiedemann syndrome and probably in predisposition to adrenocortical carcinoma.

To define more precisely, in molecular terms, the region involved in Beckwith-Wiedemann syndrome (BWS), we have studied patients with BWS and a constitutional duplication of 11p15 using eight 11p15 markers. In the first case with a de novo duplication and extra material on 11p, the region spanning pter to CALCA, excluded, was duplicated. In the second case, the rearrangement was characterized using somatic cell hybrids established with lymphocytes from the father who carried a balanced translocation t(11;18)(p15.4;p11.1). The breakpoint lay exactly in the same region. It could thus be inferred that the two sons, who were the first cases reported of BWS with dup11p15 and adrenocortical carcinoma (ADCC), carried a duplication similar to that observed in the first case. Together with evidence for specific somatic chromosomal events leading to loss of 11p15 alleles in familial cases of ADCC, it can be hypothesized that a gene involved in predisposition to ADCC maps to region 11p15.5.

[Approaching the gene of mucoviscidosis. New data]. / Approche du gène de la mucoviscidose. Nouvelles données.

We used 5 polymorphic probes strongly linked to the gene of cystic fibrosis (CF) to perform the genotypical study of 48 families with at least one child presenting with the disease. The last Km19 and XV2c probes showed a very important linkage imbalance with the CF gene (allele 2 = 6.6 kb of Km19/Pstl, chi 2 = 56; allele 1 = 2.1 kb of XV2c/Taql, chi 2 = 21). These two markers define a B haplotype which confers a relative risk of 55 to be gene carrier. From these data, the predictive value for an individual presenting with this haplotype to be heterozygous was computed to be 1/5. Presently, the risk of 1/20 for a randomized subject to be gene-carrier should be reexamined after study of this genotype. These results are very important practically, as they modify the classical data of genetic counselling concerning cystic fibrosis for the couples with a risk higher than 1/4.

[What genetic risk should suggest prenatal diagnosis for cystic fibrosis?]. / A partir de quel risque génétique proposer un diagnostic prénatal de mucoviscidose?

Prenatal diagnosis of cystic fibrosis is today possible by chemical study of amniotic fluid during the 18th week of pregnancy. We have, among 90 families seen for genetic counseling between 1972 and 1985, estimated the risk of recurrence; it was of 0.25 in 55 cases; between 0.05 and 0.16 in 30 cases, greater than 0.01 in 16 cases. Before suggesting a prenatal diagnosis, it is necessary to take as basis the risk of abortion and the reliability of the method. The first risk is well known, less 0.005, in these young women; reliability can be estimated: almost 0.01 of false wrong negative, and this number is probably overvalued if all technical conditions are perfect. In front of these risks, it seems possible to propose a prenatal diagnosis from a risk of 0.01, the families being informed of all risks. We think so to hearten some families and to make possible for them to live quietly these pregnancies, probably non undertaken without our help.

[Diagnosis and follow-up of Russel's diencephalic cachexia by echography, x-ray computed tomography and nuclear magnetic resonance]. / Diagnostic et surveillance de la cachexie diencéphalique de Russel par échographie, tomodensitométrie et résonance magnétique nucléaire.

A diencephalic astrocytoma was diagnosed by ultrasonography in a 5 months old girl with nystagmus and emaciation. A 27 months follow-up with ultrasonography, computed tomography and magnetic resonance imaging, showed an initial improvement after irradiation and afterwards the development of complications with ventricular dilatation and parenchymal calcifications.

[Genetic counseling in cancerology]. / Le counseil génétique en cancérologie.

The authors have studied the different situations that prompt a request for genetic counseling if different members of the same family suffer from cancer. Six possibilities are considered: the cancer concerned is a genetic disease per se (e.g. retinoblastoma, thyroid cancer with amyloid stroma); the genetic disease is often complicated with cancer (e.g. intestinal polyposis); the genetic disease is occasionally complicated with cancer (e.g. neurofibromatosis); cancer is part and parcel of the genetic disease (e.g. chromosomal abnormalities); in addition, there are two special situations: "cancer-prone families" and families who request genetic counseling after one single case (e.g. cancer of leukaemia in a child).

Prenatal diagnosis of familial tuberous sclerosis following detection of cardiac rhabdomyoma by ultrasound.

The authors report a case of tuberous sclerosis (TS), diagnosed by prenatal ultrasound, which was suspected by the detection of intracardiac tumours and confirmed by the family investigation. Cardiac rhabdomyomata can be visualized early on echography and must suggest this diagnosis. The place of genetic counselling and prenatal diagnosis in TS is examined.