The 18 p-syndrome. Report of four cases

Mosaic chromosome 18 anomaly delineated in a child with dysmorphism using a three-pronged cytogenetic techniques approach: a case report

Background

A plethora of cases are reported in the literature with iso- and ring-chromosome 18. However, co-occurrence of these two abnormalities in an individual along with a third cell line and absence of numerical anomaly is extremely rare.

Case presentation

A 7-year-old female was referred for diagnosis due to gross facial dysmorphism and severe developmental delay. She presented with dysmorphic features, hypo/hyper pigmentation of the skin, intellectual disability and craniosynostosis. G-banding chromosome analysis suggested mos 46,XX,psu idic(18)(p11.2)[25]/46,XX,r(?18)[30]. Additional analysis by molecular karyotyping suggested pure partial deletion of 15 Mb on 18p (18p11.32p11.21). Lastly, multiple rearrangements and detection of a third cell line (ring chr18 and interstitial deletion) of chr18 was observed by multi-color banding.

Conclusion

The current study presents a novel case of chromosomal abnormalities pertaining to chromosome 18 across 3 cell lines, which were delineated with a combinatorial approach of diagnostic methods.

18p Deletion Syndrome: Case Report with Clinical Consideration and Management

18p deletion syndrome is characterized by the deletion of short arm of chromosome 18. Presentation of this syndrome is quite variable with dysmorphic features, growth deficiencies, and mental retardation with poor verbal performance. Few patients even fail to thrive when malformations involving the heart and brain are severe. In the present article, we report an isolated case of 18p deletion in a 23-year-old female who for the first time reported to the hospital for dental problems. The patient was short statured with mental retardation and craniofacial, skeletal, dental, and endocrinal abnormalities. Such presentation warrants prompt diagnosis for effective management. Furthermore, genetic counseling for such patients and their families should be considered as a part of treatment itself.

Adults with Chromosome 18 Abnormalities

The identification of an underlying chromosome abnormality frequently marks the endpoint of a diagnostic odyssey. However, families are frequently left with more questions than answers as they consider their child's future. In the case of rare chromosome conditions, a lack of longitudinal data often makes it difficult to provide anticipatory guidance to these families. The objective of this study is to describe the lifespan, educational attainment, living situation, and behavioral phenotype of adults with chromosome 18 abnormalities. The Chromosome 18 Clinical Research Center has enrolled 483 individuals with one of the following conditions: 18q-, 18p-, Tetrasomy 18p, and Ring 18. As a part of the ongoing longitudinal study, we collect data on living arrangements, educational level attained, and employment status as well as data on executive functioning and behavioral skills on an annual basis. Within our cohort, 28 of the 483 participants have died, the majority of whom have deletions encompassing the TCF4 gene or who have unbalanced rearrangement involving other chromosomes. Data regarding the cause of and age at death are presented. We also report on the living situation, educational attainment, and behavioral phenotype of the 151 participants over the age of 18. In general, educational level is higher for people with all these conditions than implied by the early literature, including some that received post-high school education. In addition, some individuals are able to live independently, though at this point they represent a minority of patients. Data on executive function and behavioral phenotype are also presented. Taken together, these data provide insight into the long-term outcome for individuals with a chromosome 18 condition. This information is critical in counseling families on the range of potential outcomes for their child.

A Rare Association of Monosomy 18p Syndrome and Polyglandular Autoimmune Syndrome Type IIIA

We report a monosomy 18p syndrome in a male patient with polyglandular autoimmune syndrome (PAS) type IIIA. A 34-year-old mentally retarded diabetic male patient with short stature, wide earlaps, old-looking face, straight nasal bone, atrophic mouth, drooping cheeks, full teeth loss, and soft, weak and sparse white hair was admitted to the outpatient endocrinology clinic. Chromosome analysis of the patient revealed 46,XY,del(18)(p11.2). He was also diagnosed with autoimmune thyroiditis, primary hypothyroidism and diabetes mellitus type 1. We concluded that monosomy 18p syndrome may be associated with autoimmune diseases and if this is suspected, patients should be examined for an endocrine deficiency.

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

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.

Monosomy 18p

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.

Clinical and molecular characterization of individuals with 18p deletion: a genotype-phenotype correlation

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.

Molecular characterization of 18p deletions: evidence for a breakpoint cluster

PURPOSE

To determine the size and parental origin of the deletion in individuals with 18p- syndrome.

METHODS

Molecular and fluorescence in situ hybridization analyses of the pericentromeric region of chromosome 18 were performed on genomic DNA and chromosomes from study participants.

RESULTS

The majority of the breakpoints were located between markers D18S852 on 18p and D18S1149 on 18q, a distance of approximately 4 Mb. The parental origin of these deletions appears to be equally distributed, half maternally derived and half paternally derived.

CONCLUSION

The distributions of both the size and parental origin of the 18p deletions support the presence of a breakpoint cluster in the 18p- syndrome.

18p deletion syndrome with a 45, XY, t (14; 18) (p11;q11.2), -18, karyotype

A dysmorphic male child of 8 months age presented with microphthalmia, micrognathia, hypertelorism, wide anterior fontanelles, large forehead, short neck, prominent ears, macrotestis and delayed developmental milestones. The patient presented with generalised seizures hydrocephalaus and Coarctation of aorta (Pre subclavian). He also had mild hypocalcaemia with normal renal function. Cytogenetic study revealed 18p(-) picture due to translocation between 14 p & 18q. Since the spectrum of clinical expression is similar to that is seen in 18p(-) syndrome it is suggested that not only whole of 18p but part of chromosome no. 18 proximal to 18 q 11.2 may also be involved in this phenotype.

Heterotaxy with left atrial isomerism in a patient with deletion 18p

We report on a female infant with partial deletion of the short arm of chromosome 18 (del 18p) and heterotaxy with left atrial isomerism. Congenital heart defect (CHD) is found in 10% of the literature reports. Interestingly, situs abnormalities have been diagnosed in four patients with del 18p, including ours. This finding could imply that a locus or loci involved in the development of normal body situs lies within this chromosomal region. Del 18p must be consid- ered when evaluating a patient with phenotypic anomalies and CHD in lateralization defects.

A Putative Susceptibility Locus on Chromosome 18 Is Not a Major Contributor to Human Selective IgA Deficiency: Evidence from Meiotic Mapping of 83 Multiple-Case Families

Previous reports of an association between constitutional chromosome 18 abnormalities and low levels of IgA suggested that this chromosome contains a susceptibility locus for selective IgA deficiency (IgAD), the most frequent Ig deficiency in humans. IgAD is genetically related to common variable immunodeficiency (CVID), characterized by a lack of additional isotypes. Our previous linkage analysis of 83 multiple-case IgAD/CVID families containing 449 informative pedigree members showed a significantly increased allele sharing in the chromosome region 6p21 consistent with allelic associations in family-based and case-control studies and provided the evidence for a predisposing locus, termed IGAD1, in the proximal part of the MHC. We have typed the same family material at 17 chromosome 18 marker loci with the average intermarker distance of 7 cM. A total of 7633 genotypes were analyzed in a nonparametric linkage analysis, but none of the marker loci exhibited a significantly increased allele sharing in affected family members. In addition, reverse painting and deletion mapping of a panel of constitutional chromosome 18 deletions/translocations showed the presence of IgA-deficient and IgA-proficient patients with the same abnormality and did not reveal a region commonly deleted. The linkage analysis of chromosome 8 and 21 regions involved in reciprocal translocations t(8;18) and t(18;21), which were identified in two patients lacking IgA, did not disclose a significant allele sharing. Although these results do not exclude the presence of a minor predisposing locus on this chromosome, such a putative locus would confer a population risk of developing IgAD/CVID much lower than IGAD1.

Dystonia in a patient with deletion of 18p

18p- syndrome from chromosomal deletion of the short arm of chromosome 18 shows a wide range of clinical manifestations. Mental retardation is the most frequent neurological complication; other neurological deficits are more rarely reported. Only one 18p- patient with focal dystonia at the lower limbs has been reported, while there have been no reported cases of generalized dystonia. We report a 27-year-old male with 18p- de novo complete deletion (karyotype 46,XY,18p-) who was affected by severe generalized dystonia, hypokinesia, mental retardation and dysmorphic features. The 18p- syndrome should be added to the list of genetic causes of secondary dystonia. A karyotype analysis should be considered in secondary dystonias, particularly when there are associated dysmorphic features and mental retardation.

Case report: denovo inherited 18p deletion in a mother-fetus pair with extremely variable expression, confirmed by fluorescence in situ hybridization (FISH) analysis

Denovo deletions of 18p without other associated rearrangement are uncommon. For such a deletion to profoundly affect the fetus of a near normal phenotypic carrier would be rarer. We present such a case in which the chance of a cryptic rearrangement was ruled out by fluorescence in situ hybridization (FISH) analysis. Possible explanations for wide variations in clinical expression are discussed.

Mental retardation/shortness of stature/multiple minor anomalies syndrome associated with insertion of 3q material into 18p

This is a case report of a 16-year-old Arab girl with mental subnormality, shortness of stature and multiple minor phenotypic anomalies. She is obese with normal secondary sexual characteristics, and has a speech deficit. Cytogenetic studies showed a 46,XX,dir ins (18;3)(p11.1;q13.2-->q25). The chromosome arrangement appeared balanced. Her condition is not a recognizable specific syndrome; thus, it remained unclear as to whether her condition is attributable to disruption of 3q or 18p or both. Further cytogenetic analysis by molecular biologists is required to solve this problem.

A case with dicentric translocation between chromosome 9 and 18: confirmation by fluorescent in situ hybridization on metaphase spread

A female child with dicentric translocation between chromosome 9 and chromosome 18 presented non-specific minor anomalies with laryngomalacia. Chromosomal analyses were performed by the G-banding method and a fluorescence in situ hybridization (FISH) technique with a specific probe for the centromeric region of chromosome 18 and the painting probe for the chromosomes 9 and 18. Her full karyotype was confirmed as 45,XX,tdic(9;18)(p24;p11). This is the first case of dicentric translocation between chromosomes 9 and 18. The FISH technique is an important tool in chromosome diagnostics.

del(18p) syndrome with complex tetralogy of Fallot in an infant with 45,X,t(Y;18)(q12;q11.2)

We report on an infant with multiple congenital anomalies, tetralogy of Fallot, and Karyotype 45,X,t(Y;18)(q12;11.2). The infant's anomalies are consistent with a del(18p) syndrome, except for the exceptional severity of the heart defect.

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.

Syndromology: an updated conceptual overview. X. References

Part X is the reference section for Parts I through VIII which appeared in the four previous issues of the journal and Part IX which appears in this issue. The reference section itself is divided into two parts. The first part provides general references of selected topics for the interested reader. The second part consists of an alphabetical listing of all references cited in Parts I through IX.

Perspectives on holoprosencephaly: Part III. Spectra, distinctions, continuities, and discontinuities

This paper attempts to balance our knowledge of holoprosencephalic spectra and continuities with important distinctions and discontinuities. Prevalence studies and syndrome delineation are briefly reviewed. The following topics receive detailed coverage: human teratogens, special aspects of forebrain and hindbrain malformations, aprosencephaly/atelencephaly, association with neural tube defects, current assessment of "facial principles," and endocrine abnormalities.

Perspectives on holoprosencephaly: Part I. Epidemiology, genetics, and syndromology

This paper provides an updated, comprehensive, critical review of the epidemiology, genetics, and syndromic aspects of holoprosencephaly and is divided into four parts. In the first part, epidemiologic aspects are discussed under the following headings: prevalence, temporal trends, socioeconomic status, exposure to environmental teratogens, maternal and paternal ages, pregnancy histories, and birth weights. The second part analyzes the facial phenotypes because the genetic and syndromic aspects of holoprosencephaly cannot be understood without knowledge of facial variability and its meaning. Topics discussed include cyclopia, ethmocephaly, cebocephaly, median cleft lip, and less severe facial dysmorphism. The third section, on genetics, analyzes associated anomalies, chromosomal and non-chromosomal holoprosencephaly, family studies, twin studies, genetics of nonsyndromic holoprosencephaly, and recurrence risks. The final section on syndromology summarizes 48 conditions in which some degree of holoprosencephaly may be a feature.

Heart disease associated with deletion of the short arm of chromosome 18

Deletion of the short arm of chromosome 18 produces a highly variable phenotype. Mental retardation, short stature, and an abnormal facies are invariably present. About 9% of patients with this syndrome have cardiac pathology.

18p-Mosaicism: case report and review

The case of a 5-month-old male infant with 18p- mosaic, who has intractable seizures and severe ophthalmological abnormalities in addition to many clinical manifestations usually described in the 18p- syndrome, is reported. The proportions of abnormal cells are 7-8% in blood and 55% in skin. About 35% of the short arm of chromosome 18 is deleted. to our knowledge the present report is the fifth one of 18p-mosaic. The main interest of this case resides in the fact that it shows a serious clinical picture despite the low proportion of abnormal cells in blood and the small degree of deletion of the short arm of chromosome 18.

Cranial morphology in the 18p-syndrome

Three of four recently described children with the 18p- syndrome were reinvestigated using cranial computerized tomography (CCT). More severe deformities were found in the cases with severe cerebral malformation, but there was no correlation with the degree of mental retardation.

18p--syndrome resulting from 14q/18q 'dicentric' fusion translocation

A child with nasal hypoplasia, growth and developmental delay, and 18p--due to 14q/18q apparent dicentric fusion is reported. Review of ten previously reported patients with 18p--due to fusion translocations involving the long arm of chromosome 18 reveals clinical features ranging from arrhinencephaly to minimal dysmorphic changes and mild retardation. This spectrum of clinical expression is similar to that seen in patients with partial 18p deletions. Since the same range of clinical features is observed whether there is partial or apparent total deletion of 18p, it is suggested that only a distal segment of the short arm of chromosome 18 may be etiologically related to the clinical phenotype in the 18p--syndrome.