Familial distal monosomy 3p26.3-pter with trisomy 4q32.2-qter, presenting with progressive ataxia, intellectual disability, and dysmorphic features

We present a boy diagnosed with partial 3p monosomy and partial 4q trisomy. The patient was 9 years of age with intellectual disability, dysmorphic features, and ataxia. A family history and medical evaluation showed that the father manifested similar facial dysmorphic features, intellectual disability, quadriparesis, and progressive cerebrospinal ataxia. The chromosomal aberration found in the proband was inherited from his father who was found to have a balanced reciprocal translocation of chromosomes 3p and 4q, which was in turn inherited from the paternal grandfather. The final cytogenetic diagnosis according to microarray was 46,XY,der(3)t(3;4)(p26.1;q32.2)arr 3p26.1(39,066-5,363,502)x1,4q32.2q35.2(162,555,236-191,173,881)x3. We describe the cytogenetic investigations that led to the identification of the breakpoints. In addition, we present an overview of the clinical features found in patients with partial 3p monosomies and partial 4q trisomies as reported in the literature.     

Delineation of the dup5q phenotype by molecular cytogenetic analysis in a patient with dup5q/del 5p (cri du chat)

An infant girl presented with multiple congenital abnormalities and a distinctive mewing cry. Her karyotype was 46,XX,add5p. Chromosome analysis on the mother revealed an apparently balanced pericentric inversion of chromosome 5, with the precise position of the breakpoints not clearly discernable by GTG banding, 46,XX,inv(5)(p15.2/3?q35.1?). Fluorescence in situ hybridization (FISH) studies using a commercial cri du chat probe (D5S721,D5S23) revealed signals on both the normal and derivative chromosomes. Telomeric probes specific for 5p and 5q were used to confirm the pericentric inversion in the mother and demonstrated the loss of the terminal 5p region and a duplication of the terminal 5q region in the proband. The imbalance on chromosome 5 in the patient was further defined using comparative genomic hybridization (CGH), which revealed a loss of material from 5p15.3 --> pter and a gain of 5q34 --> qter. The presence of the cat-like cry appears to be the only specific feature that can be linked to the loss of 5p material. The remaining dysmorphic features of this infant appear to be due specifically to the duplication of the 5q sequences. The combination of FISH, CGH, and cytogenetics has confirmed that the characteristic cry of the cri du chat syndrome is due to the deletion of the most distal part of the classic del 5p region. More importantly, our investigation has defined the duplication of 5q34 --> qter as a distinct clinical phenotype.     

Clinical and molecular cytogenetic characterization of two patients with partial trisomy 1q41-qter: further delineation of partial trisomy 1q syndrome.

We report the clinical and molecular cytogenetic characterization of two patients with partial trisomy 1q. The first patient is a currently 11-year-old female proposita with a de novo unbalanced translocation 46,XX,der(8)(8qter-8p23.3::1q41-1qter), leading to a partial trisomy 1q41-qter and a partial monosomy for 8p23.3-pter. The most prominent clinical features of the girl are a triangular face, almond-shaped eyes, low-set ears, short stature with relatively long legs, and mild psychomotor retardation. To our knowledge, the cytogenetic aberration in this girl is the most proximal partial trisomy 1q leading to a mild phenotype. Recently, we identified a second patient with a similar partial trisomy 1q combined with a cri du chat syndrome caused by a de novo unbalanced translocation 46,XX,der(5)(5qter-5p13.1::1q41-1qter). Comparison of the phenotype of the two girls as well as with already published trisomy 1q cases was performed, and fluorescence in situ hybridization probes from selected YACs were used to delineate the extent of the partial trisomy in more detail.     

Characterization of a heritable partial monosomy 18p by molecular and cytogenetic analysis.

This report describes the fourth case of heritable 18p monosomy, which was ascertained by prenatal diagnosis. Cytogenetic analysis of amniotic fluid cells by G-banding showed an apparently distal 18p chromosome deletion and a derivative X chromosome resulting from a translocation between the X and Y chromosomes. Analysis of peripheral blood lymphocytes from the parents by G-banding revealed the same chromosome 18 deletion in the mother, who did not have the X/Y translocation. Comparative genomic hybridization (CGH) studies confirmed the loss of chromosome region 18p11.3-pter previously detected, and eliminated the presence of unbalanced reorganizations of other chromosome regions. No subtle translocation was detected by fluorescence in situ hybridization (FISH) studies using whole chromosome specific painting probes. This is a new report of a heritable 18p monosomy. Although in our case the mother had several minor congenital malformations, the loss of 18p11.3 band was not associated with any obvious phenotypic alteration in the fetus.     

Duplication of 8p23.1: a cytogenetic anomaly with no established clinical significance.

We present seven families with a cytogenetic duplication of the short arm of chromosome 8 at band 8p23.1. The duplication has been transmitted from parents to offspring in four of the seven families. In three families, the source of the extra material and its euchromatic origin were established using FISH with a YAC which was mapped to 8p23.1 and a whole chromosome paint for chromosome 8. FISH signals from this YAC were significantly larger on the duplicated chromosome compared with the normal chromosome in all six family members tested. Comparative genomic hybridisation (CGH) on a representative subject was consistent with these results. The families were ascertained for a variety of mostly incidental reasons including prenatal diagnosis for advanced maternal age. The transmission of this duplication by multiple phenotypically normal family members with no history of reproductive loss suggests the existence of a novel class of 8p23.1 duplications, which can be regarded as euchromatic variants or duplications with no phenotypic effect.     

Fryns syndrome phenotype caused by chromosome microdeletions at 15q26.2 and 8p23.1

Background: Fryns syndrome (FS) is the commonest autosomal recessive syndrome in which congenital diaphragmatic hernia (CDH) is a cardinal feature. It has been estimated that 10% of patients with CDH have FS. The autosomal recessive inheritance in FS contrasts with the sporadic inheritance for the majority of patients with CDH and renders the correct diagnosis critical for accurate genetic counselling. The cause of FS is unknown. Methods: We have used array comparative genomic hybridisation (array CGH) to screen patients who have CDH and additional phenotypic anomalies consistent with FS for cryptic chromosome aberrations. Results: We present three probands who were previously diagnosed with FS who had submicroscopic chromosome deletions detected by array CGH after normal karyotyping with G-banded chromosome analysis. Two female infants were found to have microdeletions involving chromosome band 15q26.2 and one male had a deletion of chromosome band 8p23.1. Conclusions: We conclude that phenotypes similar to FS can be caused by submicroscopic chromosome deletions and that high resolution karyotyping, including array CGH if possible, should be performed prior to the diagnosis of FS to provide an accurate recurrence risk in patients with CDH and physical anomalies consistent with FS.     

Trisomy 17p10-p12 resulting from a supernumerary marker chromosome derived from chromosome 17: molecular analysis and delineation of the phenotype

We report a 5-year-old boy with a small de novo marker chromosome derived from the proximal short arm of chromosome 17. His clinical features include hypotonia, global developmental delay, oval face with large nose and prominent ears, and ligamentous laxity of the fingers. Magnetic resonance imaging of the brain demonstrated mildly delayed myelination. G-band chromosome analysis revealed mosaicism for a small marker chromosome in 85% of the peripheral blood cells analyzed. Fluorescence in situ hybridization and microsatellite polymorphism studies showed that the der(17) was of maternal origin and included genetic material from the 17p10-p12 region, but did not contain the PMP22 gene. One breakpoint mapped within the centromere and the second breakpoint mapped adjacent to the Charcot-Marie-Tooth disease type 1A proximal low-copy repeat (CMT1A-REP). We compare the clinical characteristics of our patient with those previously reported to have a duplication involving the proximal short arm region of chromosome 17 to further delineate the phenotype of trisomy 17pl0-p12.     

2q34-qter duplication and 4q34.2-qter deletion in a patient with developmental delay

The 2q3 duplication and 4q3 deletion syndromes are two conditions with variable phenotypes including Pierre-Robin sequence (PRS), limb anomalies, congenital heart defects (CHD), developmental delays and intellectual disabilities. We describe a patient born to a mother with a balanced t(2; 4) translocation who combines both a 2q34-qter duplication and a 4q34.2-qter deletion through inheritance of the derivative chromosome 4 (der(4)). He showed developmental delay, growth retardation, hearing problems, minor facial and non-facial anomalies, such as bilateral fifth finger shortness and clinodactyly, but no PRS or CHD. The comparison of his features with those of 46 and 65 published cases of 2q3 duplication and 4q3 deletion, respectively, allows us to further restrict the size of the proposed critical intervals for PRS and CHD on chromosome 4.     

Omphalocele in trisomy 3q: further delineation of phenotype

We report a case of a patient with omphalocele, dysmorphic features, and mild developmental delay associated with a chromosomal aberration. Chromosome studies showed that the propositus carries a maternally derived unbalanced translocation der(4)t(3;4)(q27.3;q32.3), resulting in trisomy for region 3q27.3→qter and monosomy for 4q32.3→qter. Because the association between dup3q and omphalocele has been reported in several cases, we analyzed the data on 93 previously reported patients with partial trisomy of the long arm of chromosome 3 and compared the clinical features between the cases. The imbalance of chromosome 3 in the patient was further defined by fluorescence in situ hybridization (FISH) studies using bacterial artificial chromosome (BAC) clones. BAC clone RP11-171N2 was identified as a breakpoint-spanning clone in the patient and his mother. Based on our comparative analysis, we have delineated that the smallest region of overlap (SRO) associated with omphalocele is from BAC 171N2 to 3qter. We hypothesize that the SRO contains a gene(s) important in normal abdominal wall development and is of potential interest for further investigation.     

Molecular cytogenetic characterization and genotype/phenotype analysis in a patient with a de novo 8p23.2p23.3 deletion/12p13.31p13.33 duplication

Genomic copy number imbalances are being increasingly identified as an important cause of intellectual disability (ID) and behavioral disturbances. This article reports the clinical features, and long term follow-up of a patient with neurodevelopmental, cognitive, and behavioral abnormalities associated with facial dysmorphism, CNS anomalies, and epilepsy. The karyotype was normal; array CGH testing revealed a de novo cryptic aberration with a terminal 8p23.2p23.3 deletion, and a concomitant 12p13.31p13.33 duplication, of 6.86 Mb, and 8.49 Mb, respectively. Our patient clinical features are compared to those of partial 8 monosomy and/or partial 12p trisomy cases reported in literature, in order to establish genotype-phenotype correlations. For some features, for example, electroencephalogram (EEG) abnormalities and epilepsy, both abnormalities seem to make a contribution, while most phenotypic traits have been assigned to 8p monosomy or to 12p trisomy, contributing to a tentative phenotype map for partial monosomy of the short arm of chromosome 8, and trisomy of the short arm of chromosome 12.     

Trisomy 3p23----pter and monosomy 11q23----qter in an infant with two translocation carrier parents.

A newborn male infant with multiple congenital abnormalities was found to be trisomic for 3p23----pter and monosomic for 11q23----qter. His parents were both carriers of a balanced reciprocal translocation. Considerable overlap in phenotype-karyotype correlations was found between the two chromosomal syndromes in the patient.     

Supernumerary ring chromosomes in dermatofibrosarcoma protuberans may contain sequences from 8q11.2-qter and 17q21-qter: a combined cytogenetic and comparative genomic hybridization study

Dermatofibrosarcoma protuberans (DFSP) presents with characteristic cytogenetic features such as reciprocal t(17;22)(q22;q13) or, more commonly, supernumerary ring chromosomes containing sequences from chromosomes 17 and 22. Here, we report the identification of a novel abnormality in a 43-year-old woman with DFSP. Cytogenetic analysis of tumor cells showed the presence of a supernumerary ring chromosome as the sole anomaly. Amplification of 8q11.2 approximately qter and 17q21 approximately qter sequences was confirmed by comparative genomic hybridization (CGH); the present case apparently lacked amplification of chromosome 22. To our knowledge, this is the first case indicating that the ring chromosome in DFSP is possibly associated with amplified material from chromosomes 8 and 17.     

Recurrent inverted duplication of 2p with terminal deletion in a patient with the classical phenotype of trisomy 2p23-pter

Inverted duplications with terminal deletions have been reported in an increasing number of chromosomes and are probably more frequent than suspected until recently. We describe the cytogenetic and molecular characterization of an inverted duplication of chromosome 2p in an 8-year-old girl. Firstly interpreted as partial duplication 2p, the rearrangement was in fact an inverted duplication associated with a terminal deletion of the short arm of the rearranged chromosome 2, the latter not being detectable by cytogenetic analysis. The complete karyotype was: 46,XX,add(2)(p23)dn.ish inv dup del(2)(:p23.2-->p25.3::p25.3-->qter) (wcp2+,N-MYC++,2pter-)dn. We precisely define the extension of both the duplication and the deletion using bacterial artificial chromosomes clones spanning the regions. The size of the inverted duplicated segment was estimated to be 28 Mb, spanning from 2p23.2 to 2p25.3, and an approximately 1.6 Mb segment at 2pter-p25.3 was deleted in the abnormal chromosome. The physical findings noted in our patient include prominent forehead, hypertelorism, flat nasal bridge, and low-set and large ears. In addition, she had congenital heart defect and scoliosis. Her psychomotor development was severely delayed from the beginning. All these clinical features are the same as observed for the typical trisomy 2p23-pter syndrome. The phenotypic effects of the terminal deletion of 2p in addition to the trisomy are discussed. This is the third patient presenting with a severe clinical phenotype and a de novo inv dup del (2p).     

Trisomy 8 as the sole chromosomal aberration in myelocytic malignancies: a comprehensive molecular cytogenetic analysis reveals no cryptic aberrations

Involvement of the MLL gene located at chromosome region 11q23 is a frequent occurrence in both acute myelocytic leukemia and acute lymphoblastic leukemia. More than 30 loci have now been associated with MLL, usually by reciprocal translocation. Deletions, insertions, and more complex rearrangements of MLL are rarely seen. We present three cases of AML M5 showing no cytogenetic evidence of 11q23 rearrangement, in which a commercial MLL dual-color fluorescence in situ hybridization probe revealed a nonstandard abnormal signal pattern, suggesting cryptic insertion of the MLL gene into its partner gene site.     

Case of 15q26-qter deletion associated with a Prader-Willi phenotype

Prader-Willi syndrome (PWS) is one of the common neurogenetic disorders associated with intellectual disability. PWS involves a complex inheritance pattern and is caused by an absence of gene expression on the paternally inherited 15q11.2-q13 region, either due to deletion, maternal uniparental disomy or imprinting defect. The syndrome is characterized principally by severe neonatal hypotonia, a weak suck in infancy that is later followed by hyperphagia and obesity, developmental delay, intellectual disability and short stature. In the case of the chromosome 15q26-qter deletion syndrome or Drayer's syndrome, very few reports have been published. Its characteristics include intrauterine growth restriction, postnatal growth failure, varying degrees of intellectual disability, developmental delay, typical facial appearance and diaphragmatic hernia. The present paper describes a female patient in whom clinical findings were suggestive of PWS and deletion in the 15q26-qter region. Both karyotyping and methylation-specific polymerase chain reaction were shown to be normal. Nevertheless, fluorescence in situ hybridization showed a 15qter deletion that was later mapped by single nucleotide polymorphism (SNP)-array. The deleted genomic region involves the insulin-like growth factor-1 receptor (IGF1R) gene, which is related to short stature, developmental delay and intellectual disability. This case had various clinical characteristics in common with the cases of 15q26-qter deletionand characteristics compatible with PWS.     

Trisomy 2q35-q37 due to insertion of 2q material into 17q25: clinical, cytogenetic, and molecular cytogenetic characterization

We present a 7-year-old boy with growth retardation, developmental and mental delay, and minor physical abnormalities. The patient had a male karyotype with duplicated material of unknown origin in the long arm of chromosome 17. The origin of the duplicated material was clarified by fluorescence in situ hybridization. Forward chromosome painting showed that the extra material originated from chromosome 2, which was inserted into 17q25. Further characterization of the aberrant chromosome 17 by microdissection and reverse chromosome painting revealed a duplication of bands 2q35 to q37.1. To our knowledge, no other individual with a duplication of this small segment has been described so far. The clinical findings of 13 cases with isolated trisomy 2q are reviewed in relation to the size of the duplicated region. Functional analysis of the duplicated 2q region suggests that critical loci for visceral and central nervous system development in distal trisomy 2q are proximal to 2q33.