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The deletion 18p syndrome is one of the most common chromosome abnormalities. The medical problems are mental and postnatal growth retardation, and sometimes malformations of the heart and brain. The individuals have some typical features, which might be easy to overlook and which are: ptosis, strabismus, hypertelorism, broad flat nose, micrognathia, big and low set ears. The aims of present study were to clinically and molecularly characterize the syndrome further in seven subjects with de novo 18p deletions and to perform genotype-phenotype correlation. All seven subjects had terminal deletions and no interstitial deletion was observed with subtelomeric FISH analyses. To define the extent of the 18p deletions and the parental origin of the deletion microsatellite- and FISH analyses were performed on genomic DNA and on lymphoblastoid cell lines of the study participants. Totally 19 chromosomes, 18 specific polymorphic microsatellite markers, and 5 BAC clones were used. The results revealed that the deletions were located in the centromeric region at 18p11.1 in four of the seven subjects. In the remaining three the breakpoints were located distal to 18p11.1 (18p11.21-p11.22). Four of the individuals had a paternal and three a maternal origin of the deletion. Genotype-phenotype correlation of the seven subjects suggests a correlation between the extent of the deleted region and the mental development. All the four children with a deletion in the centromeric region at 18p11.1 had a mental retardation (MR). Two of the three children with a more distal breakpoint (distal 18p11.21) had a normal mental development and one had a border-line mental retardation. There might be a critical region for the mental retardation located between 18p11.1 and 18p11.21. The children with a breakpoint at 18p11.1 had all a broad face, which was observed in only one of those with a more distal breakpoint, otherwise no genotype-phenotype correlation of the features was observed.
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PMID:Clinical and molecular characterization of individuals with 18p deletion: a genotype-phenotype correlation. 1669 87

Molecular karyotyping holds the promise of improving genotype-phenotype correlations for frequent chromosome conditions such as the 18p- syndrome. In spite of more than 150 reported cases with deletions in 18p, no reliable phenotype map for the characteristic clinical findings such as mental retardation, post-natal growth retardation and typical facial features has been established yet. Here, we report on four patients with partial monosomy 18p of different sizes owing to unbalanced translocations that were thoroughly characterised clinically and by molecular karyotyping. One patient had a terminal deletion of 1.6 Mb in 18p and a trisomy of 8q24.23-qter as determined by array-based comparative genomic hybridisation and large insert clone fluorescent in situ hybridisation. In two sibs and a fourth patient, cytogenetic and molecular-cytogenetic analyses showed the terminal deletions in 18p (8.0 and 13.84 Mb, respectively) to be accompanied by partial trisomies of 20p. Literature analyses of typical phenotypic features of 18p-, 8q+ and 20p+ syndromes allowed the attribution of clinical findings in our patients to the respective chromosomal aberration. Based on these data, we propose a phenotype map for several clinical features of the 18p- syndrome: Round face was tentatively mapped to the distal 1.6 Mb of 18p; post-natal growth retardation and seizures to the distal 8 Mb and ptosis and short neck to the proximal half of 18p.
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PMID:Towards mapping phenotypical traits in 18p- syndrome by array-based comparative genomic hybridisation and fluorescent in situ hybridisation. 1702 14

Monosomy 18p refers to a chromosomal disorder resulting from the deletion of all or part of the short arm of chromosome 18. The incidence is estimated to be about 1:50,000 live-born infants. In the commonest form of the disorder, the dysmorphic syndrome is very moderate and non-specific. The main clinical features are short stature, round face with short philtrum, palpebral ptosis and large ears with detached pinnae. Intellectual deficiency is mild to moderate. A small subset of patients, about 10-15 percent of cases, present with severe brain/facial malformations evocative of holoprosencephaly spectrum disorders. In two-thirds of the cases, the 18p- syndrome is due to a mere terminal deletion occurring de novo, in one-third the following are possible: a de novo translocation with loss of 18p, malsegregation of a parental translocation or inversion, or a ring chr18. Parental transmission of the 18p- syndrome has been reported. Cytogenetic analysis is necessary to make a definite diagnosis. Recurrence risk for siblings is low in de novo deletions and translocations, but is significant if a parental rearrangement is present. Deletion 18p can be detected prenatally by amniocentesis or chorionic villus sampling and cytogenetic testing. Differential diagnosis may include a wide number of syndromes with short stature and mild intellectual deficiency. In young children, deletion 18p syndrome may be vaguely evocative of either Turner syndrome or trisomy 21. No specific treatment exists but speech therapy and early educational programs may help to improve the performances of the children. Except for the patients with severe brain malformations, the life expectancy does not seem significantly reduced.
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PMID:Monosomy 18p. 1828 72

We report two unbalanced translocations involving the short arms of chromosomes 7 and 18 due to a balanced translocation 7;18 in the mother. Karyotyping and fluorescence in situ hybridization analysis of the female fetus revealed an unbalanced subtelomeric translocation(karyotype 46,XX,der(18)t(7;18)(p22.3;p11.32)mat resulting in a partial trisomy 7p and a partial monosomy 18p.Array comparative genomic hybridization (CGH) detected a4.44-Mb heterozygous duplication at 7p22.3 to 7p22.1 and a0.178-Mb heterozygous deletion at 18p11.32. Clinical characteristics comprised a mildly stenotic bicuspid aortic valve and a small aortic arch without coarctation. The patient's older brother displayed a reciprocal version of her chromosomal aberration (46,XY,der(7)t(7;18)(p22;p11.32) resulting in a partial monosomy 7p and a partial trisomy 18p. Array CGH revealed a 4.75-Mb heterozygous deletion at 7p22.3p22.1 and a 0.579-Mb duplication at 18p11.32. He presented with tetralogy of Fallot, cleft palate, microcephalus without craniosynostosis, growth retardation, ptosis of the right eyelid, right-sided renal agenesis, unilateral cryptorchism,and mental retardation. In this report, we present the clinical phenotype in patients with aberrations of chromosomes 7p and 18p and reviewed the literature to summarize cardiovascular malformations in these patients.
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PMID:Cardiac malformation of partial trisomy 7p/monosomy 18p and partial trisomy 18p/monosomy 7p in siblings as a result of reciprocal unbalanced malsegregation--and review of the literature. 2230 61

Deletion on the short arm of chromosome 18 is a rare disorder characterized by intellectual disability, growth retardation, and craniofacial malformations (such as prominent ears, microcephaly, ptosis, and a round face). The phenotypic spectrum is wide, encompassing a range of abnormalities from minor congenital malformations to holoprosencephaly. We present a case of a 2-year-old girl with ptosis, a round face, broad neck with low posterior hairline, short stature, and panhypopituitarism. She underwent ventilation tube insertion for recurrent otitis media with effusion. Brain magnetic resonance imaging showed an ectopic posterior pituitary gland and a shallow, small sella turcica with poor visualization of the pituitary stalk. Cytogenetic and chromosomal microarray analysis revealed a de novo deletion on the short arm of chromosome 18 (arr 18p11.32p11.21[136,227-15,099,116]x1). She has been treated with recombinant human growth hormone (GH) therapy since the age of 6 months after diagnosis of GH deficiency. Her growth rate has improved without any side effects from the GH treatment. This case expands the phenotypic spectrum of 18p deletion syndrome and emphasizes the positive impact of GH therapy on linear growth in this syndrome characterized by growth deficiency. Further studies are required to define the genotype-phenotype correlation according to size and loci of the deletion in 18p deletion syndrome and to predict prognosis.
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PMID:A case of de novo 18p deletion syndrome with panhypopituitarism. 3094 82