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.     

Familial ring (19) chromosome mosaicism: Case report and review

Ring (19) chromosomal mosaicism has been identified in a 14-month-old girl referred for cytogenetic evaluation due to microcephaly and developmental delay with autistic-like mannerisms. An analysis of her peripheral blood lymphocytes showed a 46,XX,r(19) cell line in 119/121 of cells examined. Of the two remaining cells, one had a normal female chromosome complement and the other showed loss of one of the chromosome 19 homologs. Further analysis by fluorescence in situ hybridization using an all human telomere probe showed the presence of a single hybridization signal on the r(19) chromosome. Subsequent cytogenetic characterization of cells derived from the patient's phenotypically normal mother also demonstrated the presence of a ring 19 chromosome in 4/100 cells. The remaining cells had a normal female chromosome complement. These findings represent the first reported case of familial ring 19 mosaicism. The cytogenetic and clinical findings in these two individuals are discussed in relation to six previously reported cases of de novo ring chromosome 19 mosaicism. © 1996 Wiley-Liss, Inc.     

Characterization of a de novo unbalanced translocation t(14q18q) using microdissection and fluorescence in situ hybridization

We report on a patient with a de novo translocation between the long arms of chromosomes 14 and 18. The translocation was studied using microdissection in combination with fluorescence in situ hybridization (micro-FISH). Five copies of the chromosomes involved in the translocation were isolated by microdissection and amplified by means of degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR). Reverse chromosome painting with the biotin-labeled PCR product showed that part of the q-arm of chromosome 18 had no signal. The deletion was characterized further by FISH with band-specific probes and it was concluded that the rearrangement was unbalanced: 46,XY,t(14;18)(14pter→4q22::18q21.1→18qter)(18pter→18q12.2::14q22→14qter). The patient, who presented with psychomotor retardation, mild obesity, pes equinovarus, strabismus, and facial anomalies, is compared with previously reported patients with an interstitial deletion of band 18q12. Am. J. Med. Genet. 75:409-413, 1998. © 1998 Wiley-Liss, Inc.     

Monosomy 16q: a distinct syndrome Apropos of a de novo del(16) (q2100q2300)

A 2-month-old boy with delayed growth and development, brachycephaly, large anterior fontanelle, low-set folded ears, micrognathia, aortic coarctation, floppy abdominal muscles, and pes varus, was found to have a 46,XY,del(16)(q2100q2300) de novo karyotype. This observation corroborates both the distinctness of the 16q monosomy syndrome and the pathogenetic role of the band 16q21.     

A case of de novo i(12p) with 12q whole-arm translocation mosaicism

We report a dup(12p) due to a de novo i(12p) in a girl with mosaicism for 12q whole-arm translocations onto 7p, 7q, and 11q terminal regions. The dup(12p) syndrome was confirmed by clinical, cytogenetic, and LDH-dosage studies.     

Three cases of dup(10p)/del(10q) syndrome resulting from maternal pericentric inversion

Two families and 3 patients with dup(10p)/del(10q) syndrome segregating from a maternal pericentric inversion are described, including a stillborn female with Potter sequence and multicystic renal dysplasia. Comparison of 32 dup(10p) patients to 11 del(10)(q25) patients emphasized dolichocephaly, wide sutures, frontal bossing, micrognathia, and renal defects as distinguishing characteristics of the dup(10p) syndrome. The 3 new and 6 previously reported dup(10p)/del(10q) patients had several manifestations in common with the dup(10p) and del(10q) syndromes, but were more typical of dup(10p) syndromes, with respect to all 5 distinguishing characters. © 1993 Wiley-Liss, Inc.     

Tandem duplication mosaicism: characterization of a mosaic dup(5q) and review

Mosaicism for tandem duplications is rare. Most patients reported had abnormal phenotypes of varying severity, depending on the chromosomal imbalance involved and the level of mosaicism. Post-zygotic unequal sister-chromatid exchange has been proposed as the main mechanism for tandem duplication mosaicism. However, previous molecular analyses have implicated both meiotic and post-zygotic origins for the duplication. We describe a newborn male who was originally diagnosed in utero with arrhythmia and tetralogy of Fallot. He had multiple dysmorphic features including telecanthus, blepharophimosis, high broad nasal bridge with a square-shaped nose, flat philtrum, thin upper lip, down-turned corners of the mouth, high-arched palate, micrognathia, asymmetric ears, and long, thin fingers and toes. Karyotyping of peripheral blood lymphocytes showed mosaicism for a tandem duplication of part of the long arm of one chromosome 5: mos46,XY,dup(5)(q13q33)[6]/46,XY[45]. Fibroblast cultures had the same mosaic karyotype with a higher frequency of the dup(5) clone: mos46,XY,dup(5)(q13q33)[9]/46,XY[21]. Fluorescence in situ hybridization analysis with a wcp5 confirmed the chromosome 5 origin of the additional material. Parental karyotypes were normal indicating a de novo origin of the dup(5) in the proband. Molecular analyses of chromosome 5 sequence-tagged-site (STS) markers in our family were consistent with a post-zygotic origin for the duplication. Therefore, mosaicism for tandem duplications can arise both through meiotic or mitotic errors, as a result of unequal crossing over or unequal sister-chromatid exchange, respectively. Our review indicates that mosaicism for tandem duplications is likely under-ascertained and that parental karyotyping of probands with non-mosaic tandem duplications should be performed.     

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.     

Familial pericentric inversion of chromosome 18: behavioral abnormalities in patients heterozygous for either the dup(18p)/del(18q) or dup(18q)/del(18p) recombinant chromosome

We describe a family in which the largest hitherto reported pericentric inversion of chromosome 18, inv(18)(p11.22q23), segregates. Individuals heterozygous for the nonrecombinant inversion were unaffected. However, those heterozygous for either the dup(18p)/del(18q) or dup(18q) /del(18p) recombinant exhibited mild learning difficulty, personality disorders and deficient social behavior in the absence of mental retardation. Of the three family members tested, the behavioral abnormalities were more prominent in the two individuals with the dup(18p)/del(18q) recombinant than in the one with the dup(18q)/del(18p) recombinant. Genetic counseling issues for this family, in particular for the affected, include the enhanced probability of reduced fertility as well as the recurrence risk of the parental inversion equaling 1/2 in surviving offspring. This observation kindles the interest in determining the frequency of subtelomeric rearrangements in individuals with learning difficulty and deficiency in social interaction, phenotypic features often considered to be of multifactorial causation.     

Familial del(18p) syndrome

We report on sibs and their mother, all with del(18p). The propositus, an 11‐month‐old, had developmental delay, round face, hypertelorism, large ears, broad nasal bridge, upturned nostrils, micrognathia, a high palate, redundant skin around the neck, micropenis, and cryptorchidism . The elder sister, a two and 7/12‐year‐old, had round face, hypertelorism, broad nasal bridge, narrow and high palate, redundant skin around the neck, short fingers, and hypoplastic genitalia. Their mother had microcephaly, hypertelorism, prominent colu‐ mella, broad nasal bridge, wide mouth, high palate, malaligned teeth, and clinodactyly of the fifth fingers. Serial photographs of the mother showed that the characteristic round face in infancy changed to long face with age. The present report suggests that the mother with del(18p) may be fertile, and proper genetic counseling and long follow‐up is necessary for the patient with del(18p) syndrome. © Wiley‐Liss. Inc.     

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.     

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.     

Second case report of del(4) (q25q27) and review of the literature

We report a malformed infant with a de novo interstitial deletion of 4q. This is the second patient reported with del(4) (q25q27). Although there are several common features such as marked hypotonia, cardiac abnormalities, cleft palate, and micrognathia noted in our case and that of Chudley et al. (1988), we conclude from our comparison of the seven previously reported cases involving deletions of bands 4(q25q27) that a specific phenotype cannot yet be described for this deletion.     

Unique de novo interstitial deletion of chromosome 17, del(17) (q23.2q24.3) in a female newborn with multiple congenital anomalies

We describe a newborn with a novel interstitial deletion of the long arm of chromosome 17 [del (17) (q23.2q24.3)] who died on day of life 17 during a recurrent apneic episode. Her phenotype included severe growth retardation, multiple facial anomalies, maldeveloped oralpharyngeal structures, and digital and widespread skeletal anomalies. This patient's phenotype was compared to two other reported patients with deletion 17q with minor clinical overlap consistent with a unique deletion. © 1995 Wiley-Liss, Inc.     

Prenatal diagnosis of a de novo reciprocal translocation 46,XX,t(1;18) (p22;q23)

A case is reported in which a de novo balanced translocation 46,XX,t(l;18Xp22;q23) was diagnosed prenatally.     

Trisomy (18q) and tetrasomy (18p) resulting from isochromosome formation

In this paper we report two clinically recognizable chromosomal syndromes, both resulting from isochromosome 18 formation, i.e. trisomy 18q and tetrasomy 18p. The possible mechanisms of the isochromosome formation are discussed and the literature on subject is reviewed.     

Case report of rec(7)dup(7q)inv(7)(p22q22) and a review of the recombinants resulting from parental pericentric inversions on any chromosomes

We report a rare case of duplication for 7q22 → 7qter and deletion for 7p22 → 7pter, resulting from a meiotic recombination of a paternal pericentric inversion, inv(7)(p22q22). The newborn boy had the 7q trisomy syndrome. In addition, the diagnosis of chondrodysplasia punctata was made from lumbar and hand X-ray films taken soon after birth. Only two cases of rec(7)dup(7q), both in a single family, have been reported previously. We review 133 offspring with recombinations resulting from pericentric inversions on any chromosomes reported between 1981 and 1995. Of the 133 cases, 110 had a long-arm duplication and short-arm deletion, while only 23 had a short-arm duplication and long-arm deletion. In 85 of the 133 cases, the mother was an inversion carrier (five carriers had two affected offspring), and in 46, the carrier was a father (one carrier had three affected offspring). Kaiser [Hum Genet 1984;68:1–47] reviewed 63 offspring with recombinations derived from a parental pericentric inversion reported between 1972 and 1981. In both surveys, recombinations resulting from pericentric inversions of chromosomes 1, 12, 19, and Y were not found. Am. J. Med. Genet. 73:290–295, 1997. © 1997 Wiley-Liss, Inc.