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

Haploinsufficiency of CELF4 at 18q12.2 is associated with developmental and behavioral disorders, seizures, eye manifestations, and obesity

Only 20 patients with deletions of 18q12.2 have been reported in the literature and the associated phenotype includes borderline intellectual disability, behavioral problems, seizures, obesity, and eye manifestations. Here, we report a male patient with a de novo translocation involving chromosomes 12 and 18, with borderline IQ, developmental and behavioral disorders, myopia, obesity, and febrile seizures in childhood. We characterized the rearrangement with Affymetrix SNP 6.0 Array analysis and next-generation mate pair sequencing and found truncation of CELF4 at 18q12.2. This second report of a patient with a neurodevelopmental phenotype and a translocation involving CELF4 supports that CELF4 is responsible for the phenotype associated with deletion of 18q12.2. Our study illustrates the utility of high-resolution genome-wide techniques in identifying neurodevelopmental and neurobehavioral genes, and it adds to the growing evidence, including a transgenic mouse model, that CELF4 is important for human brain development.

Psychiatric syndromes in individuals with chromosome 18 abnormalities

Chromosome 18 abnormalities are associated with a range of physical abnormalities such as short stature and hearing impairments. Psychiatric manifestations have also been observed. This study focuses on the presentations of psychiatric syndromes as they relate to specific chromosomal abnormalities of chromosome 18. Twenty-five subjects (13 with an 18q deletion, 9 with 18p tetrasomy, and 3 with an 18p deletion), were interviewed by psychiatrists (blind to specific chromosomal abnormality) using the DIGS (subjects 18 and older) or KSADS-PL (subjects under 18). A consensus best estimation diagnostic process was employed to determine psychiatric syndromes. Oligonucleotide Array Comparative Genomic Hybridization (Agilent Technologies) was utilized to define specific regions of chromosome 18 that were deleted or duplicated. These data were further analyzed to determine critical regions of the chromosome as they relate to phenotypic manifestations in these subjects. 58.3% of the chromosome 18q- deletion subjects had depressive symptoms, 58.3% had anxiety symptoms, 25% had manic symptoms, and 25% had psychotic symptoms. 66.6% of the chromosome 18p- deletion subjects had anxiety symptoms, and none had depressive, manic, or psychotic symptoms. Fifty percent of the chromosome 18p tetrasomy subjects had anxiety symptoms, 12.5% had psychotic symptoms, and 12.5% had a mood disorder. All three chromosomal disorders were associated with high anxiety rates. Psychotic, manic and depressive disorders were seen mostly in 18q- subjects and this may be helpful in narrowing regions for candidate genes for these psychiatric conditions.

Recurrent interstitial deletions of proximal 18q: a new syndrome involving expressive speech delay

Most deletions of the long arm of chromosome 18 involve some part of the most distal 30 Mb. We have identified five individuals with cytogenetically diagnosed interstitial deletions that are all proximal to this commonly deleted region. The extent of their deletions was characterized using molecular and molecular cytogenetic techniques. Each participant was assessed under the comprehensive clinical evaluation protocol of the Chromosome 18 Clinical Research Center. Three of the five individuals were found to have apparently identical interstitial deletions between positions of 37.5 and 42.5 Mb (18q12.3-->18q21.1). One individual's deletion was much larger and extended from a more proximal breakpoint position of 23 Mb (18q11.2) to a more distal breakpoint at 43 Mb (18q21.1). The fifth individual had a proximal breakpoint identical to the other three, but a distal breakpoint at 43.5 Mb (18q21.1). The clinical findings were of interest because the three individuals with the smaller deletions lacked major anomalies. All five individuals were developmentally delayed; however, the discrepancy between their expressive and receptive language abilities was striking, with expressive language being much more severely affected. This leads us to hypothesize that there are genes in this region of chromosome 18 that are specific to the neural and motor planning domains necessary for speech. Additionally, this may represent a previously underappreciated syndrome since these children do not have the typical clinical abnormalities that would lead to a chromosome analysis.

Del(18)(q12.2q21.1) caused by a paternal sister chromatid rearrangement in a developmentally delayed girl

Monosomy of 18q12.3 has been reported in only 16 cases, in one as a mosaic with a normal cell line. Abnormal behaviour, developmental delay, normal measurements, and minor facial anomalies including ptosis, bilateral epicanthus, strabismus, short and slightly down-slanting palpebral fissures, and full cheeks are characteristic manifestations. We report on a 26-month-old girl with del(18)(q12.2q21.1) and typical phenotype. Microsatellite mediated haplotype analysis showed approximately 12 Mb deletion and demonstrated that the deletion was most likely formed during paternal meiosis by a rearrangement between the grandpaternal sister chromatids.

Long-term survival in a patient with del(18)(q12.2q21.1)

The 18q- syndrome is relatively common among cytogenetic abnormalities occurring in approximately 1 in 40,000 live births. However, interstitial deletions involving 18q12.2 to q21.1 are much less common. Only 15 cases have been reported in the literature. A phenotypic pattern is emerging of mild dysmorphic features, mental retardation, behavior abnormalities, and the lack of serious malformations. We present a 67-year-old woman with minor dysmorphic features, moderate mental retardation, hyperphagia, and del(18)(q12.2q21.1). This patient is presented for the natural history of this deletion syndrome as well as the behavioral phenotype.

Three cell line mosaicism involving structural and numerical abnormalities of chromosome 18 in a 3.5-year-old girl: 47,XX,+18/47,XX,+del(18)(q22)/46,XX

We report on a 3.5-year-old girl with a mosaic karyotype including full trisomy 18, normal cells and a majority of cells with partial trisomy involving an extra chromosome 18 deleted at band q22. She had cardiac and CNS anomalies, dysmorphic facial features failure to thrive and developmental delay. A gastrostomy tube was placed at 2 years of age. The combination of improved nutrition and optimal developmental therapy has led to her sitting supported, attempting to stand and enhancement of her cognitive and non-verbal communication abilities. Molecular investigation of the patient and her parents using microsatellite analysis has led to the conclusion that, as expected, the additional copy of chromosome 18 constituting the full trisomic cell line is maternal meiosis I in origin. The data, however, indicate that in the trisomic cell line containing the deleted chromosome 18q, the structurally abnormal 18 was of paternal origin. We think this case is the first described with both structural and numerical trisomic mosaicism involving chromosome 18 in a liveborn infant. We propose a mechanism of origin and review the literature, comparing the clinical presentation of this case with individuals having full or partial trisomy 18.

Dental caries history in nine children with chromosome 18p deletion syndrome

Chromosome 18p deletion syndrome is caused by the deletion of a portion of genetic material on the short (p) arm of chromosome 18. Many of 100 prior case reports in the medical literature describing the dental health of subjects with this syndrome reported multiple caries associated with the syndrome. At the third annual international conference of The Chromosome 18 Registry & Research Society, dental examinations were carried out on nine children with chromosome 18p deletion syndrome and five of their unaffected siblings. The dental examination included an intra-oral evaluation of coronal decay and filled permanent teeth surfaces (DFS) and decayed and filled primary tooth surfaces (dfs) using a mouth mirror, explorer, and a high-intensity fiber optic light. An evaluation of the data revealed that five of nine children with 18p deletion syndrome (56%) were free of tooth decay or a history of tooth decay. Four of the nine (44%) had tooth decay or a history of tooth decay. The prevalence of decay was quite similar in the genetically unaffected siblings. Three of the five (60%) unaffected siblings of the children with 18p were free of tooth decay, whereas two of the five (40%) had tooth decay. One of the affected children had a missing mandibular left central incisor. None of the children had abnormally shaped teeth. The caries pattern seems to be similar to that reported in the NHANES III data collected in the United States from 1988-1991. Analysis of these preliminary data suggests that the risk for caries in chromosome 18p deletion syndrome may be lower than previously reported.

Anterior segment malformations in 18q- (de Grouchy) syndrome

The authors examined two patients with deletions of the terminal end of the long arm of chromosome 18. The ocular findings in one patient with 46, XX, del 18 (q21) consisted of hypertelorism, epicanthus, strabismus, myopia, microphthalmia, microcornea, corneal opacities, iris hypoplasia with full thickness defects, corectopia and large peripapillary staphylomata. The second patient with 46, XX, del (18) (pter --> q21.2 :: q22 --> qter), inv (21) (q21 --> p12 :: q21 --> qter) only had epicanthus, strabismus, myopia and peripapillary crescents. Based on the findings in these two patients and on a review of previously reported patients with del 18 qter it appears that the loss of band 18q23 may be responsible for malformations of the anterior segment in the 18q-syndrome.