Maternal translocation t(13:18)(q34:q11) and Edwar''s syndrome in a fetus: 47, XY, t(13:18)(q34:q11) + 18

A 32-year-old woman, who presented with four spontaneous abortions, was found to have a balanced translocation: 46,XX,t(13:18)(q34:q11). In the last pregnancy an amniocentesis was done. Abnormal constitution of the fetus had been detected: 47,XY,t(13:18)(q34:q11) + 18, and an abortion was induced. Examination of the fetal tissue confirmed the finding. The fetus showed the characteristics of Edward's syndrome. Through the patient's pedigree it was discovered that balanced translocation appeared in three generations.     

Isochromosome (18q) in siblings

A report is presented on a familial occurrence of isochromosome (18q) in a newborn infant and in a fetus in the 24th week of gestation after amniocentesis.     

Prenatal detection of monosomy 18p and trisomy 18q mosaicism with unexpected fetal phenotype.

A mosaic karyotype 46,XX,del(18)(p11)/46,XX,-18,+?i(18q) was found in cultured amniotic cells. Fetal blood sampling confirmed the presence of both cell lines. The pregnancy was terminated and the two cell lines were demonstrated in varying proportions in the fetal tissues. The few abnormal features seen in the fetus may represent a mild expression of the 18p-- phenotype inhibiting the effects of the trisomy 18q.     

Cryptic familial t(11;18)(q25;q23) incidentally detected by interphase FISH

During a prospective prenatal study of numerical abnormalities of chromosomes 13, 18, 21, X and Y using locus-specific probes, we incidentally found a case with only one signal for chromosome 18 per cell in a chorionic villus sampling (CVS) associated with an otherwise apparently normal G-banded karyotype. This led us to discover a cryptic t(11;18) segregating in a four-generation family. The CVS was performed because of mental retardation in the brother to the father of the fetus. A subtelomeric chromosome 18 probe revealed one signal on 18qter and one on 11qter of the father. Thus the father had a balanced reciprocal t(11;18) in spite of the apparently normal G-banded karyotype. Using the same probes, we found an unbalanced translocation 46,XX,-18,+der (18)t(11;18)-(q25;q23)pat in the fetus. Further investigation of the family showed the translocation in balanced and unbalanced form in four generations in mentally normal and retarded individuals, respectively. The study emphasizes the need for a follow-up with molecular cytogenetic techniques in dysmorphic and retarded children.     

Inherited 18q23 duplication in a fetus with multiple congenital anomalies

We report on a fetus with multiple congenital anomalies including atypical lissencephaly, corpus callosum agenesis, cerebellar hypoplasia, cleft palate, ventricular septal defect, and hypoplastic aortic arch. The initial routine chromosome study failed to detect any abnormality. Subtelomeres analysis by MLPA identified an 18q23 duplication inherited from its healthy father. We describe the anomalies identified and discuss diagnosis and the causability of this telomeric duplication.     

First non-mosaic case of isopseudodicentric chromosome 18 (psu idic(18)(pter --> q22.1::q22.1 --> pter) is associated with multiple congenital anomalies reminiscent of trisomy 18 and 18q- syndrome

Isopseudodicentric chromosome 18 is very rare and results in a combination of partial trisomy and partial monosomy of chromosome 18. We report here a hypotrophic newborn with a lateral cleft lip and palate and multiple craniofacial dysmorphisms, a combined heart defect, unilateral hypoplasia of the kidney, bilateral aplasia of thumbs, and generalized contractures. Cytogenetic analysis revealed an isopseudodicentric chromosome 18 with breakpoint in 18q (46,XX,psu idic(18)(pter --> q22.1::q22.1 --> pter)). The isopseudodicentric chromosome 18 was observed in 100% of blood lymphocytes and umbilical cord fibroblasts, thus indicating a non-mosaic finding of the isopseudodicentric chromosome in the child. An elongated derivative chromosome 18 had also been found prenatally in amniotic cells. In contrast, a terminal deletion (18q-) was detected in placental cell cultures. The breakpoint was mapped to a 0.9 Mb region on 18q22.1 (located 64.8-65.7 Mb from the telomere of the p-arm) by a novel quantitative PCR approach with SYBR green detection. The results indicate an identical breakpoint of the isopseudodicentric chromosome 18 in the child and the 18q- chromosome in the placenta. To our knowledge this is the first report that a fetus carrying an isopseudodicentric chromosome 18 with breakpoint in 18q (46,XX,psu idic(18)(pter --> q22.1::q22.1 --> pter)) in non-mosaic form can be viable, but is associated with severe congenital malformations of the child.     

Duplication 18q syndrome

Some variation in the phenotype of patients with dup(18q) is recognized. Our patient has the phenotype described for dup(18qter).     

Trisomy 18 and 18p- features in a case of isochromosome 18q [46,XY,i(18q)]: prenatal diagnosis and autopsy report

This paper reports the prenatal diagnosis and autopsy findings of a case of true isochromosome 18q [46,XY,i(18q)] with severe cephalic malformations. Comparison is made with other cases of i(18q).     

Partial 18q trisomy and 18p monosomy resulting from a maternal pericentric inversion, inv(18)(p11.2q21.3).

A 7-year-old boy with dysmorphic features was found to have a recombinant chromosome 18, rec(18), resulting from meiotic recombination of a maternal pericentric inversion, inv(18) (p11.2q21.3), as defined by high-resolution banding. He was trisomic for the long arm (q21.3-qter) and monosomic for the short arm (p11.2-pter) of chromosome 18. His clinical features were compared with those in other rec(18) cases, and also those in monosomy 18p, trisomy 18qter and full trisomy 18 syndromes. The risk of recombinant formation for inv(18) carriers was also discussed.     

Partial 18q trisomy and 18p monosomy resulting from a maternal pericentric inversion,inv(18)(p11.2q21.3)

A 7-year-old boy with dysmorphic features was found to have a recombinant chromosome 18, rec(18), resulting from meiotic recombination of a maternal pericentric inversion, inv(18) (p11.2q21.3), as defined by high-resolution banding. He was trisomic for the long arm (q21.3-qter) and monosomic for the short arm (p11.2-pter) of chromosome 18. His clinical features were compared with those in other rec(18) cases, and also those in monosomy 18p, trisomy 18qter and full trisomy 18 syndromes. The risk of recombinant formation for inv(18) carriers was also discussed.     

The antenatal diagnosis of trisomy 18

The antenatal diagnosis of a fetus with trisomy 18 in a 41-year-old woman is reported. The pregnanzy was temindtcd and the diagnosis confirmed cytogenetically and morphologically. The pathological findings in the fetus are discussed.     

Features of trisomy 18 and 18p-syndromes in an infant with 46, XY, i(18q)

An isochromosome for the long arm of chromosome number 18 - 46,XY,i(18q) - was found in an infant who had features of both trisomy 18 and 18p- syndromes. Findings compatible with trisomy 18 included postmature delivery, prominent occiput, severe congenital heart disease, overlapping fingers, and rocker-bottom feet. Those of 18p- syndrome, which frequently resembles Turner syndrome, were downward obliquity to the palpebral fissures, short, webbed neck, low posterior hairline, and widely-spaced nipples. The infant died of heart failure at 3.5 months of age. Parental karyotypes were normal.     

Trisomy 18q: 46, XX,13q+,t(13;18)(q32;q11) in a newborn associated with multiple congenital anomalies due to paternal reciprocal translocation, 46, XY,-13,+der(13)/t(13;18)(q32;q11)

A 20-day-old female neonate presented with multiple congenital anomalies, convulsions and failure to thrive. Karyotype analysis of the proposita revealed an unbalanced translocation, 46, XX,13q+,t(13;18)(q32;qll)pat resulting in partial trisomy 18q. Her father and a 5-year-old sister were phenotypically normal, balanced translocation carriers, 46, XY, -13, + der(13),t(13;18)(q32;qll) and 46, XX,-13,+der(13),t(13;18)(q32;qll), respectively. The case presented here is the second liveborn reported with trisomy 18q and is of interest from the point of view of the structural chromosomal aberration resulting in the manifestations of most features of trisomy 18 and some of 13q monosomy. The infant died due to convulsions at the age of 2 months.     

Cytogenetic investigation of a child with a mosaic isochromosome 18q and ring 18q

We report on a baby girl from non-consanguineous Palestinian parents with intrauterine growth retardation, low birth weight, and developmental delay. She had a short stature, microcephaly, a prominent metopic suture, a glabellar haemangioma, exophthalmos, hypertelorism, upslanting palpebral fissures, horizontal nystagmus, flat nose, cleft lip and palate, a short neck, widely spaced nipples, umbilical hernia, flexion deformity of the wrist, ulnar deviation of fingers, and right club foot. Cortical atrophy, enlarged ventricles, a thin corpus callosum, thoracic hemivertebrae, and a ventricular septal defect were detected as well. High resolution chromosome analysis identified in 92% of cells an isochromosome 18 and in 8% of cells a ring 18. Molecular cytogenetic investigations confirmed that it was an i(18q) and a r(18q). The hypothesis to account for this anomaly and its corresponding phenotype are discussed.     

Interstitial deletion of chromosome 18[del(18)(q11.2q12.2 or q12.2q21.1]

A 27-month-old boy with mild developmental delay, growth delay, strabismus, midface hypoplasia, relative telecanthus, downslanting palpebral fissures, epicanthal folds, dental hypoplasia, and cardiac defects was found to have an interstitial deletion of chromosome 18 involving band q12.1 or q12.3.     

Interstitial deletion of chromosome 18[del(18)(q11.2q12.2 or q12.2q21.1].

A 27-month old boy with mild developmental delay, growth delay, strabismus, midface hypoplasia, relative telecanthus, downslanting palpebral fissures, epicanthal folds, dental hypoplasia, and cardiac defects was found to have an interstitial deletion of chromosome 18 involving band q12.1 or q12.3     

A pseudoisochromosome 18q and an isodicentric chromosome 18

A case of pseudoisochromosome 18q of prezygotic origin and a case of isodicentric chromosome 18 of postzygotic origin are presented to validate the differentiation between a true isochromosome and a pseudoisochromosome. This differentiation may be useful in elucidating the mechanism of the origin of an isochromosome.     

Duplication 18q21.31-q22.2

We report on three siblings with mild mental retardation and minor dysmorphic features carrying an interstitial duplication of the long arm of chromosome 18 inherited from a healthy mosaic carrier mother. The duplicated region spanned between 18q21.31 and 18q22.2 for about 12 Mb. The distal duplications of 18q are rare and only a small number of subjects, manifesting quite different clinical outcomes, have been described. However, in most of these cases, molecular characterization was not available. We have reviewed nine patients, including three familial cases, displaying overlapping duplicated regions, and compared them with the present individuals in an attempt to delineate karyotype-phenotype correlation.