[Folic acid should be administered to all pregnant women. Good assurance against neural tube defects in children].
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Biomedical subjects
Publications and source records attributed to G Annerén.
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The observation that thyroid disease is frequent in mothers of children with Down syndrome (DS) has suggested that maternal thyroid antibodies could be a factor predisposing to trisomy 21 in their offspring. In this study, the incidences of thyroglobulin (Tg) and thyroid peroxidase (TPO) antibodies were analysed with a sensitive solid-phase immunosorbent radioassay in sera from 29 mothers giving birth to children with trisomy 21 and 87 control mothers. The serum samples were collected at delivery. There was no statistical difference regarding the proportion of thyroid antibodies (against Tg and/or TPO) in the two groups. Thyroid antibodies were detected in 6/29 (20.7 per cent) of the DS mothers and in 23/87 (26.4 per cent) of the control mothers. Among the women with thyroid antibodies, 4/6 (66.7 per cent) of the DS mothers and 12/23 (52 per cent) of the control mothers had antibodies against both Tg and TPO. There was no increase in the relative risk of having a child with DS if the titre of either Tg or TPO antibodies or both were positive, i.e. > or = 1/5. The results indicate that the presence of thyroid antibodies in the serum of a pregnant women has no prognostic value for the birth of an infant with DS.
Noonan syndrome, multiple lentigines syndrome (LEOPARD syndrome), Watson syndrome and neurofibromatosis type 1 share certain clinical manifestations. We present a linkage analysis using microsatellite markers located in the neurofibromatosis type 1 region at 17q11 in a family with Noonan syndrome and café-au-lait spots and in another family with multiple lentigines syndrome. No linkage of the disease to the neurofibromatosis type 1 locus was found in the families investigated. On the basis of our results, we suggest that neither familial multiple lentigines syndrome nor Noonan syndrome is caused by a defect in the neurofibromatosis type 1 gene.
There are numerous clinical conditions observed in persons with Down syndrome, as described above, which should be taken into consideration in the course of their medical care and management. If provided with optimal medical services, pursuing specific evaluations and examinations, with a focus on preventive aspects and fostering well being in all areas of human functioning, the quality of life of individuals with Down syndrome can be enhanced significantly and their contribution to society substantial.
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During 7 years (1985-1992), 39,105 consecutive prenatal diagnoses (34,908 amniocenteses and 4197 chorionic villus samples) were made at the five largest clinical genetic laboratories in Sweden. Thirty-one cases of extra structurally abnormal chromosomes (ESACs) were found, giving a total prevalence of 0.8 per 1000. Twelve ESACs were inherited, 14 were de novo and in five the parental origin was unknown. This gives an estimated prevalence of 0.3-0.4 per 1000 for familial and 0.4-0.5 per 1000 for de novo ESACs. Retrospectively, the ESACs were characterized by fluorescence in situ hybridization (FISH). In nine cases, no material was available for this analysis. In 21 of the remaining 22 cases, the chromosomal origin could be identified by FISH. Seventeen of these (81 per cent) were derived from the acrocentric chromosomes, of which 13 originated from chromosome 15 (62 per cent). The most common ESAC was the inv dup(15) (57 per cent). Two cases were derived from chromosome 22, one from chromosome 14, and one from either chromosome 13 or chromosome 21. The four remaining cases consisted to two i(18p)s and two small ring chromosomes derived from chromosomes 4 and 19, respectively.
Defects in cytochrome oxidase (CO; complex 4) have recently been demonstrated in blood platelets and in brain tissue from patients with Alzheimer's disease (AD) with possible etiological implications. Because of pathogenetic similarities with AD, we have measured the activities of several mitochondrially localised enzymes in the blood platelets of individuals afflicted with trisomy-21 (Down's syndrome). The activities of monoamine oxidase, cytochrome oxidase, isocitrate dehydrogenase, and glutamate dehydrogenase were assayed in washed platelets from sixty caucasian, male and female control individuals (ages 18-60) and ten, young Down's Syndrome patients (ages 9-21). Significant reductions in the activities of monoamine oxidase, cytochrome oxidase, and isocitrate dehydrogenase were found. In all cases the average activities in Down's syndrome individuals were approximately two-thirds those of controls (DS/Controls = 0.68, 0.67, 0.64 respectively). The activity of the fourth enzyme studied, glutamate dehydrogenase, was found to be similar to controls. Results suggest that these reductions are a consequence of a generalised mitochondrial disturbance which may lie behind some pathogenetic aspect(s) of the disease.
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A family with an X-linked mental retardation syndrome involving seven children in two generations is reported. The syndrome includes microcephaly, severe mental retardation, optic atrophy with severely impaired vision or blindness, a severe hearing defect, spasticity, epileptic seizures, restricted movement of the large joints, and death in infancy or early childhood. We conclude that this is a distinct, previously unrecognized X-linked mental retardation syndrome.
Between 6 months and 3 years of age, growth velocity in children with Down's syndrome (DS) is markedly reduced in comparison to that of healthy children. However, after 3 years of age, it is almost normal. Thus, growth retardation becomes pronounced during the period when growth hormone (GH) starts to regulate growth. The present authors report the long-term effects of GH-therapy in 16 children with DS, who are being treated for 3 years from the age of 6-9 months. The treatment, Genotropin, 0.1 U kg-1 BW day-1, was started at a mean age of 7.4 (6-9) months. The results after 12 (n = 16), 24 (n = 12) and 30 (n = 8) months are presented. The mean height standard deviation score, SDS (range; Swedish standard), before therapy was -1.8 (-0.5 to -3.1) and the mean head circumference was -1.2 (-0.4 to -3.5). After 12, 24 and 30 months, the mean height SDS were -1.1 (-0.8 to -1.9), -0.9 (0 to -1.5) and -0.9 (0.1 to -1.5) and the mean head circumference SDS were -1.1 (0 to -2.5), -1.1 (0 to -2.2) and -1.2 (-0.5 to -2.0), respectively. During hGH-treatment, the children with DS thus gained height during the first year, and then followed the growth rate of healthy Swedish children. When compared to growth charts for children with DS the mean height of these children started at the fiftieth centile and reached the ninety-fifth centile after 24 months of treatment. Head circumference only slightly increased during the therapy, and not to the same extent as height. This indicates that small head circumference in DS is not only an effect of growth retardation, but also due to microcephaly.
Down syndrome (DS), the most common postnatally viable human autosomal chromosomal abnormality is caused by trisomy for chromosome 21. The mechanism whereby the supernumerary chromosome 21 contributes to the pathology of DS remains elusive. There are, however, several evidences that DS is a gene dosage disease. This means that overproduction of certain proteins, encoded by normal genes on the extra chromosome, distorts the delicate balance of some biochemical pathways that are important for proper development and function of the organs affected in DS. It has been shown that only the distal segment of the long arm of chromosome 21 is involved in the pathogenesis of DS. Great efforts to define this "DS specific" segment are made today, with the aim to find the "DS responsible" genes. It is suggested that as few as 10-20 genes might be responsible for the DS phenotype. We will report from a world-wide collaboration study and especially the result from one single patient. It is a woman with a characteristic phenotype of DS, but with microscopically normal karyotype. She had a sister with DS, who is dead. The parents were related, why an autosomal recessive disorder is suspected. Autoradiograms of quantitative Southern blots of DNAs from the patient and her parents were analyzed after hybridization with unique DNA sequences regionally mapped on chromosome 21. The patient seems to have three alleles at the VTNR-polymorphism in the Col6A1 gene, one copy from the father and two copies from the mother. The Col6A1 gene is mapped at the very distal segment of the long arm of chromosome 21 (21q22.3). She has only two alleles of all loci analyzed proximal to Col6A1. This might indicate that she has trisomy only for the very distal part of band 21q22.3. It is, however, not enough to find the genes within the "DS specific" segment. The metabolic gene dosage effects from these genes must be evaluated. Although several genes have been mapped on chromosome 21, not one single feature of DS has been proved to be an effect of any single gene. As an example of the difficulties to assign features of DS to chromosome 21 specific genes the gene dosage effects of the superoxide dismutase type I (SOD-1) will be presented.
Five cases with small supernumerary ring chromosomes are characterized at the molecular level. Routine chromosome banding analysis was insufficient for identification of the ring chromosomes, and none of them was DA/DAPI positive. Fluorescence in situ hybridization utilizing repetitive centromeric probes for all chromosomes has determined that one of these five ring chromosomes originates in each of chromosomes 4, 7, 8, 9, and 20. Chromosome painting with chromosome-specific libraries has confirmed this and excluded the involvement of additional chromosomes in the rearrangements.
A four-generation Swedish family with a new type of X-linked mental retardation syndrome was recently reported by Gustavson et al. The complex syndrome includes microcephaly, severe mental retardation, optical atrophy with decreased vision or blindness, severe hearing defect, characteristic facial features, spasticity, seizures, and restricted joint motility. The patients die during infancy or early in childhood. Twenty-one family members, including two affected males, were available for study. Linkage analysis was conducted in the family by using 11 RFLP markers and 10 VNTR markers spread along the X chromosome. A hypervariable short tandem repeat of DXS294 at Xq26 showed a peak two-point lod score of 3.35 at zero recombination fraction. Calculations using the same markers revealed a multipoint peak lod score of 3.65 at DXS294. Crossover events with the centromeric marker DXS424 and the telomeric marker DXS297 delimit a probable region for the gene localization. It is noteworthy that hte disease loci of two other syndromes with overlapping clinical manifestations recently were shown by Turner et al. and Pettigrew et al. to be linked to markers at Xq26.
The cytogenetic findings of an alpha-fetoprotein (AFP)-producing hepatoblastoma in a 14-month-old girl are reported. Ten of 36 tumor cells were chromosomally abnormal, yielding the composite karyotype 47,XX,2q +, t(3;5)(p25;q31),dup(4)(q12q26), +20. Three of the chromosomal abnormalities (2q+, break at 4q12, +20) have been reported previously and might be of pathogenetic significance.
A single base substitution in exon 10 of the glucocerebrosidase gene was detected in families affected by Gaucher disease (GD) type III. This mutation, which results in the substitution of proline for leucine in position 444 of glucocerebrosidase, has been shown to result in type III GD in a Swedish population. Three fetuses at risk for GD type III were diagnosed as homozygous for the mutation and the pregnancies were terminated. In a fourth pregnancy, one parent was excluded as being a carrier and the risk of having a child affected by GD was ignored. Direct analysis of common mutations causal to GD is now available and improves prenatal diagnosis in families where the molecular defect has been characterized.
An infant with thoracic spina bifida, myelomeningocele and hydrocephalus was found to have intrathoracic gastric duplication and noncontiguous tubular duplication along two-thirds of the small bowel. The myelomeningocele was closed and the hydrocephalus relieved with a shunt. The intrathoracic duplication was excised in toto and the intra-abdominal malformation successfully treated by stripping the entire mucosal tube from within the duplication.