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A family is described in which a mother and two of her children were mosaic for a small supernumerary ring chromosome. As the origin of the ring chromosome could not be determined by routine cytogenetic studies, fluorescent in situ hybridization was performed, which indicated that the ring chromosome was derived from the pericentromeric region of chromosome 7. Further characterization with a YAC-probe showed the involvement of the proximal q-arm of chromosome 7. Both sibs had speech difficulties and were mildly mentally retarded whereas the mother's intelligence was at the lower end of the normal range. They all had an unusual face, characterized by a fiat profile, short forehead, downslant of the palpebral fissures, high and broad nasal bridge, simply formed ears, and prognathia. This is the second report of a small supernumerary ring chromosome derived from the pericentromeric region of chromosome 7, and the described clinical phenotype differs from that delineated in the previous report. (C) 2000 Wiley-Liss, Inc.

We report on a boy with a maternal uniparental disomy for chromosome 14 (UPD(14)). At 7 years of age he was referred to us by the paediatrician because of symptoms of Prader-Willi syndrome (PWS). He showed short stature, obesity, mild developmental delay, cryptorchidism, and some mild dysmorphic features. The history further indicated intrauterine growth retardation at the end of the pregnancy. His mother was 44 years of age at the time of his birth. After birth he showed hypotonia with poor sucking, for which gavage feeding was needed. Motor development was delayed. After 1 year he became obese despite a normal appetite. Recurrent middle ear infections, a high pain threshold, and a great skill with jigsaw puzzles were reported. There were no behavioural problems or sleep disturbance. Chromosomal analysis was normal (46,XY). DNA analysis for Prader-Willi syndrome showed no abnormalities. Two years later he was re-examined because we thought his features fitted the PWS-like phenotype associated with maternal UPD(14). At that time precocious puberty was evident. DNA analysis showed maternal heterodisomy for chromosome 14. In all the previously described 11 cases with maternal UPD(14), a Robertsonian translocation involving chromosome 14 was detected cytogenetically before DNA analysis. This is the first report of diagnosis of maternal UPD(14) based on clinical features. This finding underlines the importance of DNA analysis for maternal UPD(14) in patients with a similar PWS-like phenotype even without previous identification of a Robertsonian translocation involving chromosome 14. Keywords: uniparental disomy; chromosome 14; genomic imprinting; Prader-Willi syndrome

To date, approximately 30 patients have been described with a tetrasomy 9p, all being caused by the presence of an isochromosome 9p, We now report on a 3-year-old boy with a de novo intrachromosomal triplication of 9p13-p22, resulting in partial tetrasomy 9p, We compared his phenotype with cases of tetrasomy 9p caused by the presence of an extra isochromosome 9p. He has facial anomalies similar to those of cases of tetrasomy 9p, central nervous system abnormalities, and severe psychomotor retardation but no other major congenital anomalies. Fluorescence in situ hybridization with region-specific probes showed that the middle repeat of the triplicated part is inverted. Microsatellite analysis demonstrated an involvement of both paternal chromosome 9 homologues in the triplication, This is compatible with either unequal crossing over of three of the four chromatids in paternal meiosis I or with a double crossing over in meiosis I and II (or an early mitotic division). (C) 1999 Wiley-Liss, Inc.

A boy with typical tetramelic split hands and feet is described. In addition, there was a large arteriovenous malformation of the right arm. Chromosome studies showed a pericentric inversion of chromosome 7: 46,XY,inv(7)(p22q21.3). Inspection of the extremities and chromosome studies in the parents were normal. This case confirms the suggested localisation of a locus, important for early limb differentiation, on the long arm of chromosome 7, most probably in the chromosomal region 7q21.2-7q21.3. Previously reported cases are reviewed briefly.

We describe a 1-year-old boy with a rare de novo 46,XY/47,XY,+ i(5p) mosaicism (ratios 28/3 in peripheral blood lymphocytes and 2/12 in skin fibroblasts). The boy, born after a pregnancy of 34 weeks, had lung hypoplasia, persistent hypotonia, and postnatal growth failure. Craniofacial anomalies were also present. His clinical manifestations correspond to those described in trisomy 5p patients. Prenatal diagnosis on maternal age indication had shown normal male chromosomes in 16 cells in the short term culture of a chorionic villus sampling. Retrospectively, 1 out of 217 cells in this culture showed the i(5p). Several mechanisms could have resulted in the formation of this 46/47, + i(5p) mosaic. Postzygotic local incorrect ligation during chromatid replication, followed by a second replication offers an attractive model on theoretical grounds since it needs only one step to explain both isochromosome formation and mosaicism. Differences between the various tissues in selection pressure on cells with the isochromosome might explain the different ratios of mosaicism found. (C) 1993 Wiley-Liss, Inc.

We report a prenatal case of a maternally inherited abnormal chromosome 16, originally interpreted as a pericentric inversion only, but after family studies re-interpreted as a pericentric inversion (16) accompanied by an unbalanced (7;16) translocation. Because of the inversion 16 and an elder son with developmental delay and craniofacial dysmorphic features, in the past karyotyped as 46,XY, the chromosomes 16 of the mother and son were carefully re-examined. Using a whole chromosome 16 paint and sub-telomere probes of 16p and 16q, the karyotype of the mother was shown to be 46,XXinv(16)(p11.2q23.2).ish der(7:16)(q36 p13.3)inv(16). Subsequently one chromosome 16 of the elder son appeared to be a der(16)t(7:16)(q36,p13.3). This is probably the result of a meiotic crossover between the chromosomes 16 in the mother. The prenatal karyotype was finally interpreted as 46,XY,inv(16)(p11.2q23.2).ish der(16)t(7:16)(q36:p13.3)inv(16). This is the same cytogenetic imbalance as his elder brother: a partial trisomy of chromosome 7 (q36 --> qter) and a partial monosomy of chromosome 16 (p13.3 --> pter). Copyright (C) 2001 John Wiley & Sons, Ltd.

Mutations in two major cancer susceptibility genes, BRCA1 and BRCA2 , predispose to early onset breast and ovarian cancer. Since 1994, genetic testing for germline mutations in these genes has been carried out in many countries in both diagnostic and research settings. Mutation analysis is usually done on the basis of a (family) history of breast or ovarian cancer—for example, (very) early age of onset, multiple affected close relatives, multiple tumours in one patient, and breast cancer in men.1–3 Ethnic background may also play a role in decisions about DNA testing, as in some populations founder BRCA1 or BRCA2 mutations are known to occur at relatively high prevalence (for example, 185delAG and 5382insC in BRCA1 and 6174delT in BRCA2 in Ashkenazi Jews4). In recent years several families have been described in which more than one BRCA mutation segregated, predominantly involving Ashkenazi Jewish founder mutations. These reports describe families that harbour two pathogenic BRCA1 mutations,5 one BRCA1 and one BRCA2 mutation,6,7,8,9,10,11,12,13,14,15,16,17 or even three pathogenic mutations in BRCA genes.18 Some of these families were uncovered because the index case appeared to carry two (founder) mutations, and only rarely was co-segregation of two different mutations suspected beforehand on the basis of the family history. This has led to the recommendation that one should always test for all three founder mutations in individuals of known Jewish ancestry.19 However, DH has also been reported without prior knowledge of Jewish ancestry.10,12,13,16,17,20 In this paper we present four new cases with mutations in both BRCA1 and BRCA2 and review and update the 30 cases reported in the literature, in order to investigate the phenotypic consequences of double heterozygosity (DH)—that is, the …

Mosaicism for a balanced reciprocal translocation (BRTM) is rare. As far as we know only 26 cases of BRTM, demonstrated in lymphocyte cultures, have been described, five of which had an abnormal phenotype. Prenatally three confirmed cases with a normal phenotypic outcome have been described. Here we present three further cases of BRTM in lymphocyte cultures. The first was detected during a family study, the second after an abnormal karyotype in chorionic villus sampling, and the third because of a history of stillborn children, All three carriers have normal phenotypes, An inventory of the BRTM cases reported so far is made. Am. J. Med. Genet. 79:362-365, 1998, (C) 1998 Wiley-Liss, Inc.

We report on a 22-year-old woman and her al-year-old brother with mild mental retardation, long face, prominent forehead, retrognathia, and (relative) macrocephaly. At birth they were small for date, their length is now below the 10th centile. Chromosome analysis demonstrated a nearly pure trisomy 1q42-->qter in both patients due to unbalanced segregation of a paternal reciprocal balanced translocation 46, XY, t(1;15) (q42;p11). This is the second report of a nearly pure trisomy 1q42-->qter. When comparing the manifestations of our patients with those of other reported cases we conclude that the most characteristic clinical manifestations of this syndrome are macrocephaly, prominent forehead, micro/retrognathia, large fontanelle, intrauterine growth retardation, postnatal growth retardation, and mental retardation. (C) 1995 Wiley-Liss, Inc.

We report on the clinical and pathologic findings in a girl with isochromosome 18q (46, XX,i(18q)) who had combined manifestations of monosomy 18p and trisomy 18q. Major congenital anomalies included premaxillary agenesis, alobar holoprosenphaly, double outlet right ventricle, DiGeorge anomaly and streak ovaries. The clinical spectrum in i(18q) is very broad. (C) 1993 Wiley-Liss, Inc.