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.     

Thymus deficiency in an infant with a chromosome t(18;22)(q12.2;p11.2)pat rearrangement

The finding of an unbalanced t(18;22)pat chromosome rearrangement in a boy with multiple anomalies including apparent absence of the thymus is described. The observation is of interest because of the reported association of chromosome 22 rearrangements with the DiGeorge sequence. In contrast to previous reports of this association, the deletion involving chromosome 22 is confined to the short arm.     

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.     

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.     

Novel isodicentric chromosome 18 in an abnormal infant with a mosaic karyotype [46, XY/46,XY, –18,+ dic(18)(q12.2)]

A previously unreported isodicentric chromosome 18 was discovered in an abnormal infant boy whose mosaic karyotype was 46, XY/46,XY,–18, + idic(18)(q12.2). His constellation of congenital anomalies was typical of the 18q-syndrome. The clinical and cytogentic characteristics of this patient are reported, and the literature concerning isochromosomes of 18 is reviewed.     

Partial deletion of 18p and partial duplication of 18q caused by a paternal pericentric inversion

Here we report on a boy with both a partial deletion of chromosome 18p and a partial duplication of chromosome 18q, caused by a paternal pericentric inversion (46, XY, rec(18), dup q, inv(18)(p11.2q21.1)pat). The findings in the patient are compared to those in the literature. The symptoms in the described patient can be explained for the major part by the 18p—and 18q+ syndromes separately. A specific 18p-/18q+ syndrome cannot be clearly delineated yet. Inspiratory stridor is a symptom that has not been described before in either 18p—or 18q +, but has been found twice before in patients with the combined 18p—/18q+ syndrome.     

t(1;18)(q32.1;q22.1) associated with genitourinary malformations

We report a male infant who has impaired penile development, hypospadias, and mild developmental delay with a 46,XY,t(1;18)(q32.1;q22.1) karyotype. Fluorescent in situ hybridization (FISH) was performed to more precisely map the translocation breakpoint. The translocation breakpoint maps to a region that has been implicated in genitourinary malformations in the 18q- syndrome. This case report suggests that a gene involved in genitourinary development maps at or near the chromosome 18 translocation breakpoint.     

Partial trisomy 11q due to paternal t(11q;18p); further delineation of the clinical picture

We describe an eleven-months-old girl with a partial trisomy 11q due to a paternal t(11;18)(q142;p14131). Clinical symptoms include severe psychomotor retardation, microcephaly, cleft palate, large, beaked nose, micrognathia, short hands and proximally placed thumbs. Moreover, a partial agenesis of the callosal body and a perineal mid-line malformation are present. The clinical picture of the index case is compared with relevant findings in patients with a partial trisomy (11 q) and partial monosomy (18p) (Aksu 1977).     

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.     

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. © 2001 Wiley‐Liss, Inc.     

Low-level complex mosaic with multiple cell lines affecting the 18q21.31q21.32 region in a patient with de novo 18q terminal deletion

We describe a 5-year-old girl who was diagnosed at birth with 18q de novo homogeneous deletion at G-banding karyotype. Her clinical condition, characterized by hypotonia, psychomotor retardation, short stature, deafness secondary to bilateral atresia of the external auditory canals, was in agreement with the 18q deletion syndrome though presence of coloboma of a single eye only suggested a mosaic condition as an unusual sign. By combining multiple technologies including array-CGH, FISH, and WGS, we found that the terminal deletion 18q21.32q23 (21 Mb) was in segmental mosaicism of the proximal region 18q21.31q21.32 (2.7 Mb), which showed a variable number of copies: one, two, or three, in 7, 41 and 55% of the cells respectively. Breakpoint junction analysis demonstrated the presence of an inv-dup del (18q) with a disomic segment of 4.7 kb between the inverted and non-inverted copies of the duplicated region 18q21.31q21.32. From these results, we propose that all three types of abnormal chr18 (the inv-dup del and the two 18q terminal deletions of different sizes) arisen from breaks in a dicentric mirror chromosome 18q, either in more than one embryo cell or from subsequent breaking-fusion-bridge cycles. The duplication region was with identical polymorphisms as in all non-recurrent inv-dup del rearrangements though, in contrast with most of them, the 18q abnormality was of maternal origin. Taking into account that distal 18q deletions are not rarely associated with inv-dup del(18q) cell lines, and that the non-disjunction of chromosome 18 takes place especially at maternal meiosis II rather than meiosis I, multiple rescue events starting from trisomic zygotes could be considered alternative to the postmitotic ones. From the clinical point of view, our case, as well as those of del(18q) in mosaic with the dic(18q), shows that the final phenotype is the sum of the different cell lines that acted on embryonic development with signs typical of both the 18q deletion syndrome and trisomy 18. Asymmetrical malformations, such as coloboma of the iris only in the right eye, confirm the underlying mosaicism regardless of whether it is still detectable in the blood.     

一例15q11.2微重复患儿的临床及遗传学分析

目的明确1例发育迟缓、智力低下患儿遗传学病因及其来源,并对该家系下一胎行产前诊断。方法采集患儿及其父母外周血进行常规G显带核型分析及单核苷酸多态性微阵列芯片(single nucleotide polymorphism array,SNP array)检测;并对该孕妇行产前诊断,进行羊水细胞染色体核型分析及SNP array检测。结果患儿及其父母染色体核型未见异常。SNP array检测结果显示患儿15号染色体15q11.2区段存在855.3 kb重复,该重复遗传至表型正常的母亲,父亲检测结果未见异常。孕妇羊水细胞染色体核型及SNP array检测结果均未见异常。结论15q11.2微重复可能与体格/智力发育障碍相关,CYFIP1可能是其候选基因,但该重复仅可增加其发病风险,外显率较低,在临床咨询中应引起重视。     

Interstitial deletion 5p accompanied by dicentric ring formation of the deleted segment resulting in trisomy 5p13-cen

Karyotypes with an interstitial deletion and a marker chromosome formed from the deleted segment are rare. We identified such a rearrangement in a newborn infant, who presented with macrocephaly, asymmetric square skull, minor facial anomalies, omphalocele, inguinal hernias, hypospadias, and club feet. The karyotype 46,XY,del(5) (pter→p13::cen→qter)/47,XY, + dicr(5)(:p13→cen::p13→cen), del(5)(pter→p13::cen→qter) was identified by banding studies and FISH analysis in the peripheral lymphocytes. One breakpoint on the del(5) maps distal to GDNF, and FISH analysis using an α-satellite probe suggests that the proximal break-point maps within the centromere. The dicentric r(5) consists of two copies of the segment deleted in the del(5), resulting in trisomy of proximal 5p (5p13-cen). The phenotype of the propositus is compared with other trisomy 5p cases and possible mechanisms for the generation of this unique chromosomal rearrangement are discussed. © 1996 Wiley-Liss, Inc.     

Case report of de novo dup(18p)/del(18q) and r(18) mosaicism

This is a report of a 27-year-old woman with an unusual de novo chromosomal abnormality. Mosaicism was identified in peripheral blood cells examined by standard G-bands by trypsin using Giemsa (GTG) analysis and fluorescence in situ hybridization (FISH) analysis with chromosome-18 region-specific probes, 46,XX,del(18)(pter → q21.33:)[41], 46,XX,r(18)(::p11.21 → q21.33::)[8], and 46,XX,der(18)(pter → q21.33::p11.21 → pter)[1]. On the other hand, the karyotype of periodontal ligament fibroblasts was nonmosaic, 46,XX, der(18)(pter → q21.33::p11.21 → pter)[50]. All cell lines appeared to be missing a portion of 18q (q21.33 → qter). The pattern of the dup(18p)/del(18q) in the rod configuration raises the possibility of an inversion in chromosome 18 in one of the parents. However, no chromosomal anomaly was detected in either parent. The most probable explanation is that de novo rod and ring configurations arose simultaneously from an intrachromosomal exchange. The unique phenotype of this patient, which included primary hypothyroidism and primary hypogonadism, is discussed in relation to her karyotype.     

Insulin dependent diabetes mellitus (IDDM) and autoimmune thyroiditis in a boy with a ring chromosome 18: additional evidence of autoimmunity or IDDM gene(s) on chromosome 18

A 4 year 3 month old boy with insulin dependent diabetes mellitus (IDDM), autoimmune thyroiditis, slight mental retardation, facial dysmorphism, and a de novo ring chromosome 18 (deletion 18q22.3-18qter) is described. This unique association of defects could represent a chance association. Alternatively, the clinical features could be the result of the chromosomal aberration. If so, one could speculate that a gene or genes on chromosome 18 might act as a suppressor or activator of the autoimmune process by itself or in concert with other IDDM loci.