Trends in prenatal diagnosis of Down syndrome and other autosomal trisomies in Scotland 1990 to 1994, with associated cytogenetic and epidemiological findings

The present report summarizes findings on 670 cases of autosomal trisomy diagnosed in Scotland, with actual or expected dates of delivery in 1990 to 1994 inclusive. Cases were notified by cytogenetic service laboratories. There were 277 prenatal and 369 postnatal diagnoses and 24 spontaneous losses. Excluding the latter, numbers diagnosed with trisomy 21, trisomy 18, trisomy 13, and other trisomies were, respectively, 470 (72.8%), 108 (16.7%), 36 (5.6%), and 32 (5.0%). Estimated maternal age-specific birth rates for trisomy 21 were close to published values from other jurisdictions. However, comparisons with a clinically based national register of congenital anomalies suggested that 3-4% of Down syndrome births were never karyotyped, most being early neonatal deaths. There was a striking increase over the period in the proportion of cases detected prenatally, associated with increased maternal serum screening in mothers <35 years old. Over the 3 final years (1992-1994), prenatal screening followed by elective termination was estimated to reduce the birth rate in trisomy 21 by 24% in mothers aged <35 years, by 57% in older mothers, and by 35% in all mothers. The crude incidence per 1,000 births fell from 1.08 in 1990-1991 to 0.77 in 1992-1994, in spite of an upward shift in the overall maternal age distribution. For trisomies 18 and 13, the estimated overall reductions in the birth rate over the whole 5-year period were respectively, 26 and 17%. In free trisomy 18, there was a significant reduction in the sex ratio (male/female) to 0.65, in line with earlier studies.

Ectrodactyly-mandibulo-facial dysostosis: case report and delineation of an entity

We describe a 24-year-old woman with tetramelic ectrodactyly, mandibulo-facial dysostosis and cleft uvula. This rare association has previously been reported in two families, but with ectrodactyly affecting only the feet. We propose the new term ectrodactyly-mandibulo-facial dysostosis for this entity.

Apparent Fryns' syndrome and aneuploidy: evidence for a disturbance of the midline developmental field

A premature male infant is described in whom the presence of coarse facies, diaphragmatic hernia, genital anomalies and Dandy-Walker malformation suggested a diagnosis of Fryns' syndrome. Lymphocyte karyotype revealed a partial trisomy 22, and his mother carried an apparently balanced 11/22 translocation. Three infants have been described recently with features of Fryns' syndrome and various aneuploidies. It is suggested that amplified developmental instability of the midline developmental field may account for some of the phenotypic resemblances between these cases.

Interstitial deletion of chromosome 13: prognosis and adult phenotype

A de novo interstitial deletion of chromosome 13 (46,XY,del(13)(pter----q14.3::q22.3----qter] is described in a 22 year old man with severe mental retardation, poor language development, low set ears, hypertelorism, broad nasal bridge, short hands and fingers, and a history of swallowing disorder in childhood with subsequent dyspepsia. The dysmorphic features did not become evident until later childhood, supporting the view that karyotyping should be performed routinely in all children with developmental delay.

Prenatal diagnosis of a case of 46,XY,18p-/46,XY,18p+ mosaicism

A case of mosaicism involving structural abnormality of chromosome 18 found in cultured amniotic fluid is reported.

Structural rearrangements in the parents of children with primary trisomy 21

A retrospective cytogenetic study was carried out on the parents of children with regular trisomy 21 Down's syndrome. In a total of 128 parents referred routinely to our laboratory after the birth of their affected child, three structural abnormalities, a reciprocal translocation and two pericentric inversions not involving chromosome 21, were detected. This is about 10 times the frequency expected based on current figures from consecutive newborn studies. In addition, the brother of one of nine older people with trisomy 21 referred for cytogenetic analysis for the first time was found to have a reciprocal translocation. This supports the contention made by others that an interchromosomal effect does exist in man. It is suggested that centres who routinely analyse the parents of their trisomy 21 referrals in an unbiased fashion should review their records. They will almost certainly contain useful information regarding the possible existence of this phenomenon and may even contain clues as to its nature. In addition to its undoubted scientific value, such data should prove useful in the genetic counselling of carriers of structural rearrangements.

Partial trisomy 7 (q32----qter) syndrome in two children

Two unrelated children are described with a partial trisomy 7 (q32----qter). Their phenotypes are compared with other reported cases with both this trisomy and others of the 7q arm. Several apparently useful pathognomonic features are distinguished. The phenotypic variability between trisomic persons within and between families is discussed. It is suggested that the disparate monosomies always associated with these trisomies may not make a major contribution to this variability. The importance for genetic counselling of reporting in detail the clinical appearance and development of all children with this rate trisomy is emphasised.

A paracentric inversion of 7q illustrating a possible interchromosomal effect

A family is described in which the proband has a rearranged X chromosome involving monosomy Xp and trisomy Xq, while the mother has a paracentric inversion of chromosome 7. It is suggested that the phenomenon of interchromosomal effect may link these observations. A brief review of the published and computer catalogued data on paracentric inversion in man is included.

A possible case of chronic leukoerythroblastosis associated with t(12;14)(p13;q22) in bone marrow cells

The case is presented of a 64-year-old man who has had recurrent psychiatric symptoms over several years, and now has minor evidence of a myeloproliferative disorder. He had a buccal carcinoma successfully treated 33 years previously, thus, the possibility of bone marrow infiltration has been excluded. An acquired translocation that was found in his bone marrow cells has not been previously reported in association with any neoplasm. The possible significance of the translocation to this patient is discussed.

The prenatal detection of a familial pericentric inversion of chromosome 19

A familial pericentric inversion of chromosome 19 was detected prenatally in a young primagravida. As far as the authors are aware there are no previous published reports of this rare abnormality being ascertained in this manner. The problems of counselling such a family are considered.

A familial pericentric inversion of chromosome 22 with a recombinant subject illustrating a 'pure' partial monosomy syndrome

A family in which a pericentric inversion of chromosome 22, inv(22)(p11q12), is segregating is described. Special reference is made to a unique recombinant subject with a 'pure' partial monosomy 22 syndrome of maternal origin. An attempt has been made to correlate the phenotypic abnormalities with monosomy for the segment 22q12----qter.

A familial insertion involving an active nucleolar organiser within chromosome 12

As far as the authors are aware this is the first report of the insertion of an active NOR into a non-acrocentric chromosome, although a simple translocation involving an active NOR has been previously recorded. More specifically, this case involves the non-reciprocal translocation of the centromere and stalk of an acrocentric into 12p, generating an apparently stable dicentric chromosome. The insertion is seen in three generations and may be relatively genetically benign. The abnormality is fully described by G and sequential C banding, DA/DAPI fluorescence, kinetochore staining, and Ag-NOR staining, and the findings are discussed in the light of the limited published reports of insertion in man.

De novo translocation heterozygote with three reciprocal translocations

An extremely rare case of a child with three balanced reciprocal translocations involving six different autosomes is described. These abnormalities have apparently arisen de novo and seem to have only relatively minor phenotypic effects. The meiotic possibilities are discussed and cytogenetic markers suggest that the damage may have occurred in a paternal gamete.

A complex double translocation involving four chromosomes and five breakpoints in a child with mild mental retardation

A 6-year-old boy with speech delay and mild mental retardation (IQ 82) was found to have a complex double translocation involving four chromosomes and a total of five breakpoints, two being on the same arm. This resulted in the karyotype 46,XY,t(2;4;7)(7;8)(q14;q31;q11q22;q13). As far as the authors are aware this is the first time that such a complex double translocation has been reported. Both parents had normal karyotypes.

Prenatal detection of Turner's syndrome in conjunction with trisomy 20 mosaicism (45,X/46, X, +0)

A case of Turner's syndrome, detected antenatally and complicated by the finding of trisomy 20 mosaicism in 50% of cells from each of two amniotic fluid cultures, is described. Cultures from seven fetal tissues in the subsequent abortus showed a predominance of 45,X cells, but nevertheless suggested the existence of a very low level of trisomy 20 mosaicism in three fetal tissues. The diagnostic dilemma in interpreting trisomy 20 mosaicism is discussed.