1/71. A previously unrecognised phenotype characterised by obesity, muscular hypotonia, and ability to speak in patients with angelman syndrome caused by an imprinting defect.The clinical features of angelman syndrome (AS) comprise severe mental retardation, postnatal microcephaly, macrostomia and prognathia, absence of speech, ataxia, and a happy disposition. We report on seven patients who lack most of these features, but presented with obesity, muscular hypotonia and mild mental retardation. Based on the latter findings, the patients were initially suspected of having prader-willi syndrome. dna methylation analysis of SNRPN and D15S63, however, revealed an AS pattern, ie the maternal band was faint or absent. Cytogenetic studies and microsatellite analysis demonstrated apparently normal chromosomes 15 of biparental inheritance. We conclude that these patients have an imprinting defect and a previously unrecognised form of AS. The mild phenotype may be explained by an incomplete imprinting defect or by cellular mosaicism.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
2/71. Characterization of a small supernumerary ring marker derived from chromosome 2 by forward and reverse chromosome painting.A small ring-shaped supernumerary marker chromosome (SMC) was detected in 50% of metaphase cells in an 18-month-old boy with mental retardation and multiple congenital anomalies. Conventional cytogenetic methods had failed to identify the origin of the marker. When the patient was age 11.5 years, we defined the origin of the SMC by fluorescence in situ hybridization using a battery of centromere-specific dna probes. The marker was positive with the probe for locus D2Z. More detailed characterization was achieved by using chromosome 2 arm-specific and marker-specific DNA libraries, which were constructed by microdissection of the two arms chromosome 2 and SMC with subsequent amplification of the chromosomal material by a degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR). The marker was identified as r(2)(p11.2-->q14.1). The propositus had dolichocephaly, coarse hair, low-set ears, exophthalmos, epicanthal folds, strabismus, depressed nasal bridge, high-arched palate, excess of skin on the neck, tapered fingers with mild clinodactyly, talipes varus on the right, inguinal hernia, hypogenitalism, muscular hypotonia, and mental retardation. This is the first case of SMC derived from chromosome 2 that was characterized by forward and reverse chromosome painting.- - - - - - - - - - ranking = 13keywords = chromosome (Clic here for more details about this article) |
3/71. Borjeson-Forssman-Lehmann syndrome in a woman with skewed X-chromosome inactivation.Borjeson-Forssman-Lehmann (BFL) syndrome is an X-linked recessive disorder characterized by minor facial anomalies, obesity, epilepsy, and severe mental retardation. The phenotype of male patients is usually severe, whereas that of carriers is less severe, suggesting X-linked incompletely recessive inheritance. A recent linkage study mapped the BFL syndrome gene to Xq26-q27. The etiology of the condition in female patients with full manifestations is not known, although nonrandom X-chromosome inactivation has been considered. We recently developed an assay for X-inactivation studies based on the methylation-specific polymerase chain reaction (PCR) technique. Using the methylation-specific PCR assay, a woman with typical findings of this syndrome was shown to have an extremely skewed X-inactivation pattern. This finding suggests that the full manifestations of the BFL syndrome in carriers may be caused by skewed X inactivation with a high proportion of cells in which the x chromosome with a normal gene be inactivated, leaving the x chromosome with a mutant gene active.- - - - - - - - - - ranking = 7keywords = chromosome (Clic here for more details about this article) |
4/71. 46, XY, del (3) (pter-->p25) syndrome: further delineation of the clinical phenotype.A boy with monosomy for the distal part of the short arm of chromosome 3 is described. The clinical features this patient has in common with the previously reported cases include pre- and post-natal growth delay, microcephaly, craniofacial dysmorphism and mental retardation. In addition, minor abnormalities not previously reported were observed, such as snapping thumbs, dorsiflected big toes, connecting anterior and posterior fontanelles at birth, nasolacrimal duct stenosis and double urethral meatus.Conclusion These five new clinical findings may help in further delineation of the syndrome and allow its early recognition. A complete revision of clinical findings published in literature is reported.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
5/71. Blaschkolinear malformation syndrome in complex trisomy-7 mosaicism.Results of repeated peripheral blood chromosome studies were normal in a boy with intrauterine growth retardation, short stature, moderate mental retardation, and multiple minor anomalies. At age 9 years it was recognized that the swirls of pigmentation/depigmentation on his trunk, linear streaks on his limbs, and body asymmetry were suggestive of chromosomal mosaicism. Four skin biopsies were obtained under anesthesia during a dental procedure. All showed mosaicism for a normal cell line, a line with an extra chromosome 7, and a cell line with an extra small ring. In one biopsy, there was a fourth cell line with an extra chromosome 7 and the ring. fluorescence in situ hybridization (FISH) with a chromosome 7 paint confirmed trisomy 7 and the chromosome 7 derivation of the ring. This young man's intra-uterine and postnatal growth retardation is an aneuploidy effect, whereas his asymmetry reflects a mosaicism effect that should have aroused suspicion of tissue-limited mosaicism before the development of obvious Blaschkolinear skin pigmentary dysplasia.- - - - - - - - - - ranking = 5keywords = chromosome (Clic here for more details about this article) |
6/71. Cryptic subtelomeric translocations in the 22q13 deletion syndrome.Cryptic subtelomeric rearrangements are suspected to underlie a substantial portion of terminal chromosomal deletions. We have previously described two children, one with an unbalanced subtelomeric rearrangement resulting in deletion of 22q13-->qter and duplication of 1qter, and a second with an apparently simple 22q13-->qter deletion. We have examined two additional patients with deletions of 22q13-->qter. In one of the new patients presented here, clinical findings were suggestive of the 22q13 deletion syndrome and FISH for 22qter was requested. Chromosome studies suggested an abnormality involving the telomere of one 22q (46,XX,?add(22)(q13. 3)). FISH using Oncor D22S39 and Vysis ARSA probes confirmed a terminal deletion. A multi-telomere FISH assay showed a signal from 19qter on the deleted chromosome 22. Results were confirmed with 19qtel and 22qtel specific probes. The patient is therefore trisomic for 19qter and monosomic for 22qter. The patient's mother was found to have a translocation (19;22)(q13.42;q13.31). We also re-examined chromosomes from two patients previously diagnosed with 22q deletions who were not known to have a rearrangement using the multi-telomere assay. One of these patients was found to have a derivative chromosome 22 (der(22)t(6;22)(p25;q13)). No evidence of rearrangement was detected in the other patient. Thus we have found the 22q13 deletion to be associated with a translocation in three of four patients. This report illustrates the usefulness of examining patients with hypotonia, severe language delay, and mild facial dysmorphism for this syndrome and suggests that most of these deletions may be unbalanced subtelomeric rearrangements.- - - - - - - - - - ranking = 3keywords = chromosome (Clic here for more details about this article) |
7/71. Case of partial duplication 2q3 with characteristic phenotype: rare occurrence of an unbalanced offspring resulting from a parental pericentric inversion.We report on a male infant with partial trisomy 2q (q34-->qter) resulting from a maternal pericentric inversion of chromosome 2 (p25. 2q34). The infant had clinical findings similar to the characteristic phenotype associated with a partial duplication of chromosome 2q3. Carriers of pericentric inversions of chromosome 2 have an increased risk of pregnancy loss but have only rarely been reported to have a liveborn offspring with an unbalanced chromosome constitution. This case further confirms the risks associated with a pericentric inversion of chromosome 2 and is the second report with manifestations of the trisomy 2q3 phenotype.- - - - - - - - - - ranking = 5keywords = chromosome (Clic here for more details about this article) |
8/71. Mapping of X chromosome inversion breakpoints [inv(X)(q11q28)] associated with FG syndrome: a second FG locus [FGS2]?FG syndrome is an X-linked condition comprising mental retardation, congenital hypotonia, macrocephaly, distinctive facial changes, and constipation or anal malformations. In a linkage analysis, we mapped a major FG syndrome locus [FGS1] to Xq13, between loci DXS135 and DXS1066. The same data, however, clearly demonstrated genetic heterogeneity. Recently, we studied a French family in which an inversion [inv(X)(q12q28)] segregates with clinical symptoms of FG syndrome. This suggests that one of the breakpoints corresponds to a second FG syndrome locus [FGS2]. We report the results of fluorescence in situ hybridization analysis performed in this family using YACs and cosmids encompassing the Xq11q12 and Xq28 regions. Two YACs, one positive for the DXS1 locus at Xq11.2 and one positive for the color vision pigment genes and G6PD loci at Xq28, were found to cross the breakpoints, respectively. We postulate that a gene might be disrupted by one of the breakpoints.- - - - - - - - - - ranking = 4keywords = chromosome (Clic here for more details about this article) |
9/71. Partial Xp duplication in a girl with dysmorphic features: the change in replication pattern of late-replicating dupX chromosome.In this paper we present the case of a girl at the age of 32 months with dysmorphic features, including general muscular hypotonia, developmental delay and mental retardation. The cytogenetic analysis revealed de novo partial duplication of Xp: 46,X,dup(X)(p11.23-->p22.33: :p11.23-->p22.33). To characterize the duplication, X painting, Kallman (KAL), yeast artificial chromosomes (YACs) and bacterial artificial chromosomes (BACs) covering Xp11.23-->Xp22.33 region were used. Selective inactivation of the abnormal x chromosome using HpaII digestion of the AR gene was evident. After BrdU incorporation the abnormal X was late-replicating in all lymphocytes examined. There was one peculiar exception observed: the break-point region was consistently early replicating. The replicating pattern of this region corresponded to the active x chromosome. Methylation pattern of late replicating x chromosome was studied also using antibodies against 5-methylcytosine. The pattern corresponded to the normally inactive x chromosome, with the exception of the previously observed break-point region which revealed an early replicating pattern with strong fluorescent signal, similar to the pattern of the active x chromosome. The observed phenomenon could lead to the abnormal phenotype of the patient, with some normally inactive genes of the break-point region escaping the inactivation process. The abnormal clinical findings could also be due to tissue-dependent differences in the inactivation pattern.- - - - - - - - - - ranking = 11keywords = chromosome (Clic here for more details about this article) |
10/71. tetraploidy in a 26-month-old girl (cytogenetic and molecular studies).Liveborn infants with tetraploidy are very rare in human pregnancies and usually die during the first days or months. Seven cases of liveborn infants with tetraploidy have previously been reported. Among them only two 92, XXXX infants survived for longer than 12 months. Here we report on the case of a 26-month-old girl with tetraploidy. The main clinical features of tetraploidy are facial dysmorphism, severely delayed growth and developmental delay. On the basis of molecular studies we discuss the possible origin of the additional chromosome sets in our proband. To our knowledge, this infant is the first reported case of tetraploidy who lived up to 26 months.- - - - - - - - - - ranking = 1keywords = chromosome (Clic here for more details about this article) |
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