Inv dup del(4)(:p14 --> p16.3::p16.3 --> qter) with manifestations of partial duplication 4p and Wolf-Hirschhorn syndrome

Genotype-phenotype correlation of deletions and duplications of 4p: case reports and literature review

Structural rearrangements of chromosome 4p gives rise to a group of rare genomic disorders that mainly result in two different clinical entities: Wolf-Hirschhorn syndrome (WHS) and partial 4p trisomy. The severity of the phenotype depends on the size of the deletion or locus duplication. Here, we present two unrelated individuals with a copy number variation of chromosome 4p. Inverted duplication deletions (inv dup-del) in 4p are particularly rare. Case 1 describes a 15-year-old girl with a 1.055 Mb deletion of terminal 4p, distal to the recognized critical region of WHS, and a large duplication of 9.6 Mb in size from 4p16.3 to p16.1. She had postnatal development delay, intellectual disability (especially pronounced in speech), seizure/electroencephalogram anomalies, and facial dysmorphic features. This unusual chromosomal imbalance resulted in the WHS phenotype rather than the 4p trisomy syndrome phenotype. Case 2 describes a 21-month-old boy with a 1.386 Mb terminal 4p deletion who presented with slight developmental delay, borderline intellectual disability, and seizures. Combined with previous reported cases of 4 pter del-dup or pure 4p terminal deletions, our observations suggest that terminal chromosome 4p deletion is more pathogenic than the concomitant partial 4p duplication, and some regions of the 4p terminal may have regulatory effects on the remaining region of 4p. About nine cases have been reported thus far to date, and our study delineates further genotype-phenotype correlations about terminal 4p duplication-deletions for predicting disease prognosis and patient counseling.

De Novo Inverted Duplication Deletion of 4p in a 14-Week-Old Male Fetus Aborted Due to Multiple Anomalies

Inverted duplications deletions are rare, complex, and nonrecurrent chromosomal rearrangements associated with a variable phenotype. In this case report, we described the phenotype and genotype of a 14-week-old male fetus, who was aborted after discovery of multiple anomalies (septal cystic hygroma, open abdominal wall, and a nonidentifiable lower limb). At autopsy, fluorescence in situ hybridization and array comparative genomic hybridization identified an inverted duplication with terminal deletion of 4p [46,XY,der(4)del(p16.3)dup(4)(p15.2p16.3)]. Only five genotypically similar cases have been reported, and we hope our case contribution will add meaningful to the body of knowledge.

Recombinant chromosome 4 in two fetuses - case report and literature review

Background

Recombinant chromosome 4 syndrome (rec 4 syndrome) is a rare genetic disorder, predominately resulting from a parental pericentric inversion of chromosome 4. To date, a total of 18 cases of rec (4) syndrome were published in literature. We report the first kindred of rec (4) syndrome analyzed using copy number variation sequencing (CNV-seq).

Results

A woman with two adverse fetal outcomes was described in the present study. The first fetus presented with severe intrauterine growth restriction, hyposarca, hydrothorax and ascites. The CNV-seq revealed a dup 4q and del 4p. The second fetus presented with cardiovascular disease of ventricular septal defect, overriding aorta and persistent trunk. The CNV-seq revealed a dup 4p and del 4q. We collected 18 rec (4) cases through literature review. Genotype-phenotype correlation analysis was also performed.

Conclusion

Recombinant 4 syndrome is a rare genetic disorder. It should be divided into two categories according to the alternative recombinant types. The clinical manifestations of rec (4) cases with dup 4q and del 4p are consistent with the Wolf-Hirschhorn syndrome. For cases harboring dup 4p and del 4q, the high incidence of congenital heart disease is prominent.

4p16.1-p15.31 duplication and 4p terminal deletion in a 3-years old Chinese girl: Array-CGH, genotype-phenotype and neurological characterization

BACKGROUND

Microscopically chromosome rearrangements of the short arm of chromosome 4 include the two known clinical entities: partial trisomy 4p and deletions of the Wolf-Hirschhorn critical regions 1 and 2 (WHSCR-1 and WHSCR-2, respectively), which cause cranio-facial anomalies, congenital malformations and developmental delay/intellectual disability.

METHODS/RESULTS

We report on clinical findings detected in a Chinese patient with a de novo 4p16.1-p15.32 duplication in association with a subtle 4p terminal deletion of 6 Mb in size. This unusual chromosome imbalance resulted in WHS classical phenotype, while clinical manifestations of 4p trisomy were practically absent.

CONCLUSION

This observation suggests the hypothesis that haploinsufficiency of sensitive dosage genes with regulatory function placed in WHS critical region, is more pathogenic than concomitant 4p duplicated segment. Additionally clinical findings in our patient confirm a variable penetrance of major malformations and neurological features in Chinese children despite of WHS critical region's deletion.

Complex nature of apparently balanced chromosomal rearrangements in patients with autism spectrum disorder

Background

Apparently balanced chromosomal rearrangements can be associated with an abnormal phenotype, including intellectual disability and autism spectrum disorder (ASD). Genome-wide microarrays reveal cryptic genomic imbalances, related or not to the breakpoints, in 25% to 50% of patients with an abnormal phenotype carrying a microscopically balanced chromosomal rearrangement. Here we performed microarray analysis of 18 patients with ASD carrying balanced chromosomal abnormalities to identify submicroscopic imbalances implicated in abnormal neurodevelopment.

Methods

Eighteen patients with ASD carrying apparently balanced chromosomal abnormalities were screened using single nucleotide polymorphism (SNP) arrays. Nine rearrangements were de novo, seven inherited, and two of unknown inheritance. Genomic imbalances were confirmed by fluorescence in situ hybridization and quantitative PCR.

Results

We detected clinically significant de novo copy number variants in four patients (22%), including three with de novo rearrangements and one with an inherited abnormality. The sizes ranged from 3.3 to 4.9 Mb; three were related to the breakpoint regions and one occurred elsewhere. We report a patient with a duplication of the Wolf-Hirschhorn syndrome critical region, contributing to the delineation of this rare genomic disorder. The patient has a chromosome 4p inverted duplication deletion, with a 0.5 Mb deletion of terminal 4p and a 4.2 Mb duplication of 4p16.2p16.3. The other cases included an apparently balanced de novo translocation t(5;18)(q12;p11.2) with a 4.2 Mb deletion at the 18p breakpoint, a subject with de novo pericentric inversion inv(11)(p14q23.2) in whom the array revealed a de novo 4.9 Mb deletion in 7q21.3q22.1, and a patient with a maternal inv(2)(q14.2q37.3) with a de novo 3.3 Mb terminal 2q deletion and a 4.2 Mb duplication at the proximal breakpoint. In addition, we identified a rare de novo deletion of unknown significance on a chromosome unrelated to the initial rearrangement, disrupting a single gene, RFX3.

Conclusions

These findings underscore the utility of SNP arrays for investigating apparently balanced chromosomal abnormalities in subjects with ASD or related neurodevelopmental disorders in both clinical and research settings.

Oculo-auriculo-vertebral spectrum, cat eye, and distal 22q11 microdeletion syndromes: a unique double rearrangement

An array-CGH on 19-year-old male showed a proximal 1.11 Mb duplication and a distal 1.7 Mb deletion of 22q11.2 regions flanking the Velocardiofacial/DiGeorge syndrome region that remained intact. FISH analyses revealed both abnormalities to be on the same homolog 22. This double rearrangement lead to the co-existence of two syndromes: Cat eye and distal 22q11.2 microdeletion syndromes with a rare associated phenotype of oculo-auriculo-vertebral spectrum (OAVS). A review of the literature indicates that this is the second report of a proximal duplication and the fifth report of a distal deletion and OAVS suggestive of a possible OAVS candidate gene in this region.

Inv dup del(9p): prenatal diagnosis and molecular cytogenetic characterization by fluorescence in situ hybridization and array comparative genomic hybridization

OBJECTIVE

To present molecular cytogenetic characterization of prenatally detected inverted duplication and deletion of 9p, or inv dup del(9p).

MATERIALS, METHODS, AND RESULTS

A 35-year-old primigravid woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a derivative chromosome 9, or der(9) with additional material at the end of the short arm of one chromosome 9. Parental karyotypes were normal. Level II ultrasound showed ventriculomegaly and normal male external genitalia. Repeated amniocentesis was performed at 20 weeks of gestation. Array comparative genomic hybridization revealed a 0.70-Mb deletion at 9p24.3 and an 18.36-Mb duplication from 9p24.3 to 9p22.1. The distal 9p deletion encompassed the genes of DOCK8, ANKRD15, FOXD4, DMRT1, and DMRT3. Fluorescence in situ hybridization analysis using bacterial artificial chromosome clone probes specific for 9p confirmed that the der(9) was derived from the inv dup del(9p). The karyotype of the fetus was 46,XY,inv dup del(9)(:p22.1-->p24.3::p24.3-->qter)dn or 46,XY,der(9) del(9)(p24.3) inv dup(9)(p22.1p24.3)dn. Polymorphic DNA marker analysis determined a maternal origin of the inv dup del(9p). A 512-g male fetus was subsequently terminated at 22 weeks of gestation with facial dysmorphism. The fetus had normal male external genitalia without sex reversal.

CONCLUSION

Fluorescence in situ hybridization and array comparative genomic hybridization are useful to determine the nature of a prenatally detected aberrant chromosome derived from the inv dup del. Male fetuses with inv dup del(9p) and haploinsufficiency of DMRT1 and DMRT3 may present normal male external genitalia without sex reversal.

Molecular characterization of a new patient with a non-recurrent inv dup del 2q and review of the mechanisms for this rearrangement

We report on newborn baby with microcephaly, facial anomalies, congenital heart defects, hypotonia, wrist contractures, long fingers, adducted thumbs, and club feet. Cytogenetic studies revealed an inverted duplication with terminal deletion (inv dup del) of 2q in the patient and a paternal 2qter deletion polymorphism. Microsatellite markers demonstrated that the inv dup del was maternal in origin and intrachromosomal. Intra or interchromosomal rearrangements may cause this aberration either by a U-type exchange (end-to-end fusion), an unequal crossover between inverted repeats (non-allelic homologous recombination: NAHR), or through breakage-fusion-bridge (BFB) cycles leading to a sister chromatid fusion by non-homologous end joining (NHEJ). A high-resolution oligo array-CGH (244 K) defined the breakpoints and did not detect a single copy region with a size exceeding 12.93 Kb in the fusion site. The size of the duplicated segment was 38.75 Mb, extending from 2q33.1 to 2q37.3 and the size of the terminal deletion was 2.85 Mb in 2q37.3. Our results indicate that the inv dup del (2q) is likely a non-recurrent chromosomal rearrangement generated by a NHEJ mechanism. The major clinical characteristics associated with this 2q rearrangement overlap with those commonly found in patients with 2q duplication reported in the literature.

Inverted duplications deletions: underdiagnosed rearrangements??

Molecular techniques led to the discovery that several chromosome rearrangements interpreted as terminal duplications were in fact inverted duplications contiguous to terminal deletions. Inv dup del rearrangements originate through a symmetric dicentric chromosome that, after asymmetric breakage, generates an inv dup del and a deleted chromosome. In recurrent inverted duplications the dicentric chromosome is formed at meiosis through non-allelic homologous recombination. In non-recurrent inv dup del cases, dicentric intermediates are formed by non-homologous end joining or intrastrand annealing. Some authors hypothesized that in these cases the dicentric may have been formed directly in the zygote. Healing of the broken dicentric chromosomes can occur not only in a telomerase-dependent way but also through telomere capture and circularization thus creating translocated or ring inv dup del chromosomes. In all the cases reported up to now, the duplicated region was always longer than the deleted one, but we can safely assume that there is another group of rearrangements where the deleted region is longer than the duplicated portion. In general, in these cases, the cytogeneticist will suspect the presence of a deletion and confirm it by FISH with a subtelomeric probe, but he/she will almost certainly miss the duplication. It is likely that the conventional analysis techniques used until now have led to a substantial underestimate of the frequency of inv dup del rearrangements and that the widespread use of array-CGH in routine analysis will allow a more realistic estimate. Obviously, the concomitant presence of deletion and duplication has important consequences in genotype/phenotype correlations.

Inv dup del(4)(:p13-->p16.3::p16.3-->qter) in a girl without typical manifestations of Wolf-Hirschhorn syndrome

We report on a 4-year-old girl who presented with microcephaly, multiple minor anomalies of face and limbs, congenital heart defect, hypotonia, neuropsychomotor delay, deafness and seizures. A GTG-banded karyotype identified an additional fragment of unknown origin on the terminal region of 4p. Parental karyotypes were normal. FISH analysis using a whole chromosome paint probe for chromosome 4 and subtelomere probes showed a signal on the entire add (4) chromosome and loss of the 4p subtelomere region, respectively. Additional analysis using microsatellite markers for chromosome 4 and whole-genome array comparative genomic hybridization (array-CGH) identified a duplication of the region 4p13 --> 4p16.3. Her karyotype was thus interpreted as an inverted duplication with terminal deletion of 4p: 46,XX,der(4)(:p13 --> p16.3::p16.3 --> qter). The clinical features of our patient differed from those typically observed in Wolf-Hirschhorn syndrome and were more compatible with duplication 4(p14 --> p16.3), with preservation of the WHS critical region.

Molecular cytogenetic characterization of the first reported case of inv dup del 20p compatible with a U-type exchange model

Inverted duplications with terminal deletions have been reported for an increasing number of chromosome ends. The best characterized and most frequent rearrangement reported involves the short arm of chromosome 8. It derives from non-allelic homologous recombination (NAHR) between two inverted LCRs (low copy repeats) of the olfactory receptor (OR) gene cluster during maternal meiosis. We report here on the cytogenetic characterization of the first inversion duplication deletion involving the short arm of chromosome 20 (inv dup del 20p) in an 18-month-old boy presenting with clinical signs consistent with 20p trisomy syndrome. This abnormality was suspected on karyotyping, but high-resolution molecular cytogenetic investigations were required to define the breakpoints of the rearrangement and to obtain insight into the mechanism underlying its formation. The duplicated region was estimated to be 18.16 Mb in size, extending from 20p13 to 20p11.22, and the size of the terminal deletion was estimated at 2.02 Mb in the 20p13 region. No single copy region was detected between the deleted and duplicated segments. As neither LCR nor inversion was identified in the 20p13 region, the inv dup del (20p) chromosome abnormality probably did not arise by NAHR. The most likely mechanism involves a break in the 20p13 region, leading to chromosome instability and reparation by U-type exchange or end-to-end fusion.

Subtelomeric 6p deletion: clinical and array-CGH characterization in two patients

We report on two patients with de novo subtelomeric terminal deletion of chromosome 6p. Patient 1 is an 8-month-old female born with normal growth parameters, typical facial features of 6pter deletion, bilateral corectopia, and protruding tongue. She has severe developmental delay, profound bilateral neurosensory deafness, poor visual contact, and hypsarrhythmia since the age of 6 months. Patient 2 is a 5-year-old male born with normal growth parameters and unilateral hip dysplasia; he has a characteristic facial phenotype, bilateral embryotoxon, and moderate mental retardation. Further characterization of the deletion, using high-resolution array comparative genomic hybridization (array-CGH; Agilent Human Genome kit 244 K), revealed that Patient 1 has a 8.1 Mb 6pter-6p24.3 deletion associated with a contiguous 5.8 Mb 6p24.3-6p24.1 duplication and Patient 2 a 5.7 Mb 6pter-6p25.1 deletion partially overlapping with that of Patient 1. Complementary FISH and array analysis showed that the inv del dup(6) in Patient 1 originated de novo. Our results demonstrate that simple rearrangements are often more complex than defined by standard techniques. We also discuss genotype-phenotype correlations including previously reported cases of deletion 6p.

Inverted duplication with terminal deletion of 5p and no cat-like cry

We report on a 6-year-old boy referred for cytogenetics study. A few non-specific features were observed in the newborn: hypotonia, failure to thrive, seizures, pre-auricular skin tags. Cat-like cry was not identified. No remarkable facial dysmorphism, gastrointestinal, respiratory or cardiac abnormalities were identified. At age 4 years, speech and motor skill delays were apparent. Karyotyping and FISH analysis revealed a de novo rearranged chromosome 5p, with subtelomeric deletion of 5p and a duplication of the cri-du-chat critical region. Array CGH using sub-megabase resolution tiling-set (SMRT) array followed by FISH analysis with labeled BACs showed a deletion of 5pter to 5p15.31 (0-6.9 Mb) and an inverted duplication of the greater part of 5p15.31 to the distal end of 5p14.3 (6.9-19.9 Mb). Although very rare, inverted duplications with terminal deletion (inv dup del) have been reported at different chromosomal ends. Our finding adds a second patient of inv dup del 5p to this growing list, and the potential causative mechanisms for this rearrangement are discussed. Review of the mapping information of cri-du-chat patients and the comparison with a previously reported patient suggested that the critical region for cat-like cry is located within a 0.6 Mb region.

Two mosaic terminal inverted duplications arising post-zygotically: Evidence for possible formation of neo-telomeres

Objective

To elucidate the structure of terminal inverted duplications and to investigate potential mechanisms of formation in two cases where there was mosaicism with cells of apparently normal karyotype.

Results

A karyotype [46,XY,inv dup(4)(p16.3p15.1)/46,XY] performed on blood lymphocytes from a patient referred for developmental delay (case 1) demonstrated a normal karyotype in 60% of cells with a terminal inverted duplication 4p in the remainder. In case 2, referred for multiple fetal anomalies on an ultrasound scan, 33% of amniocyte colonies were karyotypically normal, with a terminal inv dup 10p in the remainder [46,XX,inv dup(10)(p15.3p11)/46,XX]. Duplicated FISH signals for GATA3 and NEBL loci (in case 2), and for the Wolf-Hirschhorn locus (case 1) confirmed the inverted structure of both duplications. In the GTL banded normal cells from both cases, there was a cryptic deletion detected by FISH of one copy of the subtelomere 4p (case 1, probe GS-36P21), and subtelomere 10p (case 2, probe GS-306F7). At pter on both inv dup chromosomes there was no FISH signal present for the specific subtelomere probe. However, a positive pantelomeric probe signal was detected at 4 pter and 10 pter in both the cryptically-deleted chromosomes and the inv dup chromosomes in the respective cell lines of both cases.

Conclusion

An inv dup structure was evident for both cases on GTL bands, and confirmed by the various FISH studies. The presence of telomere (TTAGGG repeat) sequences at pter on the inv dup chromosomes (where more proximal chromosome specific subtelomeric probes were negative) was indicated by the pantelomeric probe signals in both cases. We conclude the most likely mechanism of origin in both cases was by sub-telomeric breakage in the zygote at pter, and delayed repair/rearrangement until after one or more subsequent mitotic divisions. In these divisions, at least one breakage-fusion-bridge cycle occurred, to produce inverted duplications. It is proposed then that two differently "repaired" daughter cells proliferated in parallel. In one daughter cell line (with an overtly normal karyotype) there was deletion of the subtelomere and presumed repair through capping by a neo-telomere (i.e. "healing", as initially proposed by McClintock). This occurred in both cases presented. In the other daughter cell of each case, it is proposed that chromosome stabilization was achieved (after replication) by sister chromatid reunion to form a dicentric, which broke at a subsequent anaphase, to form an inverted duplication (with loss of the reciprocal product, and the other daughter cell line). One inv dup was repaired without an interstitial specific subtelomere (case 1) and one was repaired with a duplicated specific interstitial subtelomere (case 2). After repair TTAGGG repeats were detected by FISH at each respective new pter.

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).

Unmasking of a hemizygous WFS1 gene mutation by a chromosome 4p deletion of 8.3 Mb in a patient with Wolf–Hirschhorn syndrome

The Wolf-Hirschhorn syndrome (WHS (MIM 194190)), which is characterized by growth delay, mental retardation, epilepsy, facial dysmorphisms, and midline fusion defects, shows extensive phenotypic variability. Several of the proposed mutational and epigenetic mechanisms in this and other chromosomal deletion syndromes fail to explain the observed phenotypic variability. To explain the complex phenotype of a patient with WHS and features reminiscent of Wolfram syndrome (WFS (MIM 222300)), we performed extensive clinical evaluation and classical and molecular cytogenetic (GTG banding, FISH and array-CGH) and WFS1 gene mutation analyses. We detected an 8.3 Mb terminal deletion and an adjacent 2.6 Mb inverted duplication in the short arm of chromosome 4, which encompasses a gene associated with WFS (WFS1). In addition, a nonsense mutation in exon 8 of the WFS1 gene was found on the structurally normal chromosome 4. The combination of the 4p deletion with the WFS1 point mutation explains the complex phenotype presented by our patient. This case further illustrates that unmasking of hemizygous recessive mutations by chromosomal deletions represents an additional explanation for the phenotypic variability observed in chromosomal deletion disorders.

Mosaicism del(22)(q11.2q11.2)/dup(22)(q11.2q11.2) in a patient with features of 22q11.2 deletion syndrome

The chromosome 22q11 region is prone to rearrangements, including deletions and duplications, due to the presence of multiple low copy repeats (LCRs). DiGeorge/velo-cardio-facial syndrome is the most common microdeletion syndrome with more than 90% of patients having a common 3-Mb deletion of 22q11.2 secondary to non-homologous recombination of flanking LCRs. Meiotic reciprocal events caused by LCR-mediated rearrangement should theoretically lead to an equal number of deletions and duplications. Duplications of this region, however, have been infrequently reported and vary in size from 3 to 6 Mb. This discrepancy may be explained by the difficulty in detecting the duplication and the variable, sometimes quite mild phenotype. This newly described 22q duplication syndrome is characterized by palatal defects, cognitive deficits, minor ear anomalies, and characteristic facial features. We report on a male with truncus arteriosus and an interrupted aortic arch, immunodeficiency, and hypocalcemia. The patient is mosaic for two abnormal cell lines: a deletion [del(22)(q11.2q11.2)] found in 11 cells and a duplication [dup(22)(q11.2q11.2)] found in 9 cells. Molecular cytogenetic analysis in our patient revealed a 1.5 Mb deletion/duplication, the first duplication reported of this size. Deletion/duplication mosaicism, which is rare, has been reported in a number of cases involving many different chromosome segments. We present the clinical phenotype of our patient in comparison to the phenotypes seen in patients with the 22q11.2 deletion or duplication alone. We propose that this rearrangement arose by a mitotic event involving unequal crossover in an early mitotic division facilitated by LCRs.

First reported case of intrachromosomal cryptic inv dup del Xp in a boy with developmental retardation

We report here on a 6-year-old boy referred to the laboratory for karyotyping and SHOX microdeletion testing. The most significant clinical findings in this boy were small stature, Madelung deformity, facial dysmorphism, mild mental retardation and behavioral problems. R-, G- and RTBG-banding chromosome analysis showed a normal male karyotype. Fine molecular characterization, by FISH, of terminal Xp microdeletion revealed an associated partial duplication. Further refinement of the molecular analysis indicated an inverted duplication of the Xp22.31-Xp22.32 (13.7 Mb) region including the STS, VCX-A and KAL1 genes, associated with a terminal Xp deletion Xp22.33-Xpter (3.6 Mb) encompassing the SHOX and ARSE genes. Such rearrangements have been characterized for other chromosomal pairs, but this is the first reported male patient involving the short arm of the X chromosome. Molecular analysis of the maternal and patient's microsatellite markers showed interchromatid mispairing leading to non-allelic homologous recombination to be the most likely mechanism underlying this rearrangement. This case highlights the importance of clinically driven FISH investigations in order to uncover cryptic micro-rearrangements.

A paternally derived inverted duplication of distal 14q with a terminal 14q deletion

A girl presented with a phenotype including neonatal hypotonia, psychomotor retardation, mental retardation, short stature, and facial dysmorphism. She demonstrated common features of both 14q31-qter duplication and terminal 14q deletion. She had undergone surgery for patent ductus arteriosus and pyloric stenosis in infancy. Her karyotype was 46,XX,der(14) dup(14)(q32.3 q31.3)del(14)(q32.3). Molecular cytogenetic analysis showed a paternally derived 14q31.3-q32.3 duplication and a terminal 14q deletion and led to the correlations between a particular genotype and phenotype. This is the first description of a deletion and inverted duplication of 14q, and adds 14q to the growing list of the inverted duplication associated with a terminal deletion.

Prenatal detection of ade novo terminal inverted duplication 4p in a fetus with the Wolf-Hirschhorn syndrome phenotype

OBJECTIVES

To present the prenatal diagnosis of a de novo terminal inversion duplication of the short arm of chromosome 4 and a review of the literature.

CASE

An amniocentesis for chromosome analysis was performed at 33 weeks' gestation because ultrasound examination showed a female fetus with multiple abnormalities consisting of severe intrauterine growth retardation, microcephaly, a cleft lip and renal hypoplasia.

RESULTS

Cytogenetic analysis and FISH studies of the cultured amniocytes revealed a de novo terminal inversion duplication of the short arm of chromosome 4 characterized by a duplication of 4p14-p16.1 chromosome region concomitant with a terminal deletion 4p16.1-pter. The karyotype was thus: 46,XX, inv dup del (4)(:p14-->p16.1::p16.1-->qter). The parents opted to terminate the pregnancy. Fetopathological examination showed dysmorphic features and abnormalities consistent with a Wolf-Hirschhorn syndrome (WHS) diagnosis, clinical manifestations of partial 4p trisomy being mild.

CONCLUSION

Although relatively rare, inverted duplications have been reported repeatedly in an increasing number of chromosomes. Only two previous cases with de novo inv dup del (4p) and one with tandem dup 4p have been reported, all of them associated with a 4pter deletion. We report the first case diagnosed prenatally. Breakpoints are variable, resulting in different abnormal phenotype. In our case, clinical manifestations resulted in a WHS phenotype.

A dysmorphic boy with 4qter deletion and 4q32.3-34.3 duplication: Clinical, cytogenetic, and molecular findings

An infant boy presented with trigonocephaly, mild craniofacial features, a small VSD, open ductus Botalli (ODB), bilateral hip dysplasia, psychomotor retardation, and hypotonia. The karyotype was 46,XY,del(4)(q34). Unexpectedly, fluorescence in situ hybridization (FISH) studies revealed not only a deletion but also a duplication. The deletion extends from 4qter to 4q34.3 and the duplication from 4q32.3 to q34.3. This is the first description of a deletion inverted duplication 4q. Possible mechanisms we can envision by which this deletion/duplication arose could be a U-type exchange causing end-to-end fusion or a two step event with a paracentric inversion and subsequent cross-over in the inverted segment. This observation suggests that the karyotype of patients with a 4q deletion should be confirmed by molecular cytogenetics.