Trisomy 18 syndrome with an unusual karyotype: possible double isochromosome.

Larson, Linda; Wasdahl, Walter A.; Saumur, J H; Coleman, Mary L.; Jalal, Syed M.

doi:10.1136/jmg.15.1.73

Cited by 24 publications

(17 citation statements)

References 7 publications

(8 reference statements)

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“…This is in contradiction to trisomy for part or all of 18q. Consequently, most cases of i(18)(q10) show features attributable to trisomy 18 and monosomy for 18p [Rabinowitz et al, 1967;Larson et al, 1978;Ramirez-Castro and Bersu, 1978;Bass et al, 1979;Froster-Iskenius et al, 1984;Spinner et al, 1991;Wurster-Hill et al, 1991;van Essen et al, 1993;Van den Berg et al, 1999;Sutcliffe et al, 2001]. The most common mechanism for isochromosome formation is centromere misdivision and whole-arm duplication resulting in monocentric products and an unbalanced rearrangement [de la Chapelle, 1982;Hecht, 1988].…”

Section: Introductionmentioning

confidence: 99%

A patient with isochromosome 18q, radial-thumb aplasia, thrombocytopenia, and an unbalanced 10;18 chromosome translocation

et al. 2005

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We report on the clinical and cytogenetic findings in a newborn with a de novo isochromosome 18q. Radial/thumb aplasia and thrombocytopenia were significant features in addition to multiple congenital anomalies. Comparison with reported cases suggests that the genes for such features are located on the 18q arm. An additional finding of a non-reciprocal translocation between chromosome 18p telomere and chromosome 10q telomere was also observed in a majority of cells examined. This additional rearrangement likely has minimal phenotypic consequences, but does raise the possibility that cryptic translocations of telomeric ends of the deleted arm in isochromosome cases may be more common than appreciated.

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Section: Introductionmentioning

confidence: 99%

A patient with isochromosome 18q, radial-thumb aplasia, thrombocytopenia, and an unbalanced 10;18 chromosome translocation

et al. 2005

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“…In two cases maternal age was 41 and 35 years, respectively, but they were ascertained by prenatal diagnosis because of advanced age [Romain et al, 1992;van den Berg et al, 1999]. Two liveborn children had young parents: mothers 23 and 25, fathers 28 and 31 years, respectively [Muller et al, 1972;Larson et al, 1978]. Our cases 1, 3, and 4 were cases of monoisodisomy and did not show advanced parental ages (Table I).…”

Section: Discussionmentioning

confidence: 59%

“…The phenotype is in the majority of cases described as very similar to trisomy 18 or Edward's syndrome. Isochromosome 18q appears in the classical form with one centromere and two q arms and have been described in about 20 cases [Van Dyke, 1988 for review of cases before 1988; Chen et al, 1998 for review of cases after 1988], as double isochromosomes together with i(18p) described in four cases [Muller et al, 1972;Larson et al, 1978;Romain et al, 1992;van den Berg et al, 1999], and as a pseudodicentric chromosome with two centromeres separated by p arm material [Laurent et al, 1978;Madan et al, 1981;Ward et al, 1981;Fioretti et al, 1982;Wulfsberg et al, 1984;Meguid and Habibian, 1992;Brandt et al, 1994;LevyMozziconacci et al, 1996;Gravholt et al, 1997] or q arm material [Floore et al, 1989;Bryke et al, 1990;Fujiwara et al, 1992;Ausems et al, 1994]. Isochromosomes are mirror duplications as they are composed of genetically identical arms.…”

Section: Introductionmentioning

confidence: 99%

DNA studies of mono‐ and pseudodicentric isochromosomes 18q

Bugge

Brandt

Petersen

2004

American J of Med Genetics Pt A

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The description of isochromosomes 18 has so far mainly been by cytogenetic studies and based on identical banding pattern of the two arms. However, only molecular techniques are capable to distinguish an isochromosome from a translocation, whole arm or reciprocal, between two chromosomes 18. We have used 23 PCR-based DNA polymorphisms to determine the parental origin and mechanisms of formation in four patients with isochromosomes 18q and to demonstrate that they were consistent with true isochromosomes. Three of the probands were liveborn children with clinical features characteristic of Edwards syndrome, one proband was a fetus diagnosed at prenatal diagnosis. In one case the isochromosome was monocentric with two identical q arms of maternal origin, formed by misdivision of the centromere and loss of p arm material. Another monocentric case had 47 chromosomes with isochromosomes i(18p) and i(18q) formed by maternal postzygotic centromeric misdivision and segregation of both isochromosomes, or by meiosis II centromeric misdivision and nondisjunction (without recombination in meiosis I). In two cases, the isochromosomes were dicentric with genetically identical arms composed of a part of the short and the whole long arm of chromosome 18 of paternal origin. The formation of the fused chromosomes can be explained by postzygotic exchange of sister chromatids on the short arm of chromosome 18, followed by breakage and U-shape reunion of sister chromatids.

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“…However, Krü ger et al (1987) reported on a familial occurrence of i(18q) in a newborn infant and in a fetus whose parents had normal karyotypes and suggested the possibility of gonadal mosaicism in one of the parents. Additionally, combined isochromosomes of both short and long arms of chromosome 18 [i(18p)+i(18q)] (Mü ller et al, 1972;Larson et al, 1978;Romain et al, 1992) and mosaic i(18q) (Baguena Candela et al, 1971;Madan et al, 1981;Sutton and Ridler, 1986;Bryke et al, 1990) have also been reported. Eight cases of i(18q) had holoprosencephaly (Froster-Iskenius et al, 1984;Shyu et al, 1988;Nyberg et al, 1989;Spinner et al, 1991;Wurster-Hill et al, 1991;van Essen et al, 1993;Chow et al, 1996;Levy-Mozziconacci et al, 1996), one had DiGeorge anomaly (van Essen et al, 1993), one had Robin anomaly (Wiswell and Edwards, 1986), one had congenital glaucoma and scalp defects (Rodiére et al, 1977), two had cryptorchidism (Kleczkowska et al, 1986;Shyu et al, 1988), one had hypoplastic external genitalia (Froster-Iskenius et al, 1984), one had omphalocoele, oesophageal atresia and tracheooesophageal fistula (Nyberg et al, 1989), two had bicornute uterus (Spinner et al, 1991), and one had uni-lobed right lung and bisexual organs with testes, uterus and cervix (Chow et al, 1996) in addition to characteristic phenotypic findings of trisomy 18 and monosomy 18p.…”

Section: Discussionmentioning

confidence: 99%

Isochromosome 18q in a fetus with congenital megacystis, intra-uterine growth retardation and cloacal dysgenesis sequence

et al. 1998

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We present the first report of a female fetus with concomitant isochromosome 18q [i(18q)] and cloacal dysgenesis sequence. Prenatal sonographic examination at 15 weeks' gestation showed intra‐uterine growth retardation, a normal brain, a normal spine, congenital megacystis and oligohydramnios. The pregnancy was terminated. The abortus displayed dysmorphic features of a high forehead, hypertelorism, a prominent nose with a bulbous tip, median cleft lip and palate, micrognathia, low‐set ears, a short neck, a joint contracture at the wrist, prominent heels and pseudo‐hermaphroditism. Necropsy confirmed an imperforate anus, megacystis, a phallic structure and cloacal dysgenesis sequence. Postnatal chromosomal investigation proved a pure de novo i(18q). Molecular genetic analysis by polymorphic microsatellite markers confirmed the maternal origin of the aberrant chromosome. The coexistence of cloacal dysgenesis sequence and i(18q) in this case shows a correlation between the disturbance of the caudal developmental field and the chromosomal abnormality with monosomy 18p and trisomy 18q. Our presentation also demonstrates the importance of perinatal cytogenetic analysis in malformed fetuses in order to uncover underlying genetic disorders. Copyright © 1998 John Wiley & Sons, Ltd.

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Trisomy 18 syndrome with an unusual karyotype: possible double isochromosome.

Cited by 24 publications

References 7 publications

A patient with isochromosome 18q, radial-thumb aplasia, thrombocytopenia, and an unbalanced 10;18 chromosome translocation

A patient with isochromosome 18q, radial-thumb aplasia, thrombocytopenia, and an unbalanced 10;18 chromosome translocation

DNA studies of mono‐ and pseudodicentric isochromosomes 18q

Isochromosome 18q in a fetus with congenital megacystis, intra-uterine growth retardation and cloacal dysgenesis sequence

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