A familial contiguous gene deletion syndrome at Xp22.3 characterized by severe learning disabilities and ADHD

Klinefelter's Syndrome with Maternal Uniparental Disomy X, Interstitial Xp22.31 Deletion, X-linked Ichthyosis, and Severe Central Nervous System Regression

We presented in this article a patient with Klinefelter syndrome (KS) (47,XXY) who had maternal nondisjunction and uniparental disomy of the X chromosome with regions of heterodisomy and isodisomy, an interstitial Xp22.31 deletion of both X chromosomes, and other problems. His mother also possesses the same Xp22.31 deletion. The patient presented with status epilepticus and stroke, followed by severe brain atrophy and developmental regression. His unusual clinical and cytogenetic findings apparently have not been reported with either KS or Xp22.31 deletions. Based on the patient's available genetic and biochemical information, we cannot satisfactorily explain his seizures, strokes, or catastrophic brain regression.

Implementation of chromosomal microarrays in a cohort of patients with intellectual disability at the Argentinean public health system

Intellectual disability is a neurodevelopmental disorder in which genetic, epigenetic and environmental factors are involved. In consequence, the determination of its etiology is usually complex. Though many countries have migrated from conventional cytogenetic analysis to chromosomal microarrays as the first-tier genetic test for patients with this condition, this last technique was implemented in our country a few years ago. We report on the results of the implementation of chromosomal microarrays in a cohort of 133 patients with intellectual disability and dysmorphic features, normal karyotype and normal subtelomeric MLPA results in an Argentinean public health institution. Clinically relevant copy number variants were found in 12% of the patients and one or more copy number variants classified as variants of uncertain significance were found in 5.3% of them. Although the diagnostic yield of chromosomal microarrays is greater than conventional cytogenetics for these patients, there are financial limitations to adopt this technique as a first-tier test in our country, especially in the public health system.

A prenatal diagnosis and genetics study of five pedigrees in the Chinese population with Xp22.31 microduplication

Background

Copy number variations (CNVs) can contribute to human phenotype, phenotypic diversity and disease susceptibility, while others may benign. In the current study, an attempt to investigate the pathogenicity of CNVs in chromosome Xp22.31 was explored.

Methods

G-banding and SNP-array techniques were used to analyze chromosome karyotypes and CNVs in fetuses. Parents associate with five different pedigrees possessing high risk factors in pregnancy were considered with such parameters as advanced age, high risk of serological screening and ultrasound abnormalities.

Results

The fetuses’ amniotic fluid karyotypes were 46, XX and those of their parents with the five pedigrees revealed no abnormalities. Here, we noticed a series of individuals with Xp22.31 duplications ranging from 534.6 kb to 1.6 Mb. It was detected through SNP array that the fetuses in Pedigree 1 and 2 had ~ 600 kb duplications in the Xp22.31 region of their X chromosomes which contained two OMIM genes, HDHD1 (OMIM: 306480) and part of STS (OMIM: 300747). The fetuses of Pedigrees 3, 4 and 5 had 1.6 Mb duplication in the same chromosome which contained four OMIM genes: HDHD1 (OMIM: 306480), STS (OMIM: 300747), PNPLA4 (OMIM: 300102) and VCX (OMIM: 300229). The duplications in the fetuses of Pedigrees 1 and 5 were inherited from the non-phenotypic parents. Pedigrees 3 and 4 refused to perform parental verification. Finally, four of the five pedigrees continue towards pregnancy with no abnormalities being observed during followed-ups.

Conclusion

Our study first showed duplications of Xp22.31 in Chinese population. Clinical and genetic investigation on five different pedigrees, we consider the duplication of these fragments as likely benign copy number variants (CNVs). We suggest that the duplications of Xp22.31 with recurrent duplication as a benign CNVs .

Unbalanced 14;X Translocation and Pattern of X Inactivation in a Female Patient with Multiple Congenital Anomalies

We report on a female patient who was first evaluated at the age of 6 years with developmental delay, dysmorphic facial features, seizures, and autistic behavior. A brain CT showed complete agenesis of the corpus callosum, and EEG recorded bilateral epileptogenic foci. Karyotype analysis revealed 45,X,psu dic(14;X)(p11;p22). FISH using 14q and Xp subtelomeric probes, combined with a SHOX gene-specific probe, and centromere X and XIST gene analysis revealed ish psu dic(14;X)(D14S1420+; DXYS129-, SHOX-, DXZ1+, XIST+). Array CGH detected a 2-Mb loss at Xp22.33 and a 4.6-Mb gain at Xp22.2p22.12. The deletion contains 34 genes, of which CSF2RA and SHOX are OMIM morbid genes. The duplication also contains some OMIM morbid genes, of which CDKL5, NH5, RPS6KA3, and AP1S2 are the most important. The late replicating chromatin technique was used to detect the pattern of X inactivation in the normal X and in the translocated chromosome. The translocated X was found to be inactive in 70% of the studied blood lymphocytes with patchy extension of inactivation to chromosome 14. In conclusion, the phenotype of the patient may be partially affected by the haploinsufficiency of the genes that are known to escape X inactivation and that lie within the deleted region and by other deleted or duplicated genes on the abnormal X chromosome due to an alternative pattern of X inactivation. The phenotype of the patient was significantly aggravated and complicated by the functional monosomy of some genes on chromosome 14 due to partial spreading of inactivation and silencing of those genes. This case report indicates the importance of structural and functional studies and emphasizes the clinical importance of the follow-up of abnormal microarrays.

A Girl with 10 Mb Distal Xp Deletion Arising from Maternal Pericentric Inversion: Clinical Data and Molecular Characterization

Background:

Short arm deletions of the X-chromosome are challenging issues for genetic counseling due to their low penetrance in population. Female carriers of these deletions have milder phenotype than male ones, considering the intellectual ability and social skills, probably because of the X-chromosome inactivation phenomenon.

Case report:

A female patient with a 10Mb distal Xp deletion and an Xq duplication, showing mild intellectual disability, is described in this report. While the deletion arose from a maternal pericentric inversion, the duplication was directly transmitted from the mother who is phenotypically normal.

Conclusion:

This report underlines the usefulness of molecular cytogenetic technics in postnatal diagnosis.

SHOX haploinsufficiency presenting with isolated short long bones in the second and third trimester

Haploinsufficiency of the transcription factor short stature homeobox (SHOX) manifests as a spectrum of clinical phenotypes, ranging from disproportionate short stature and Madelung deformity to isolated short stature. Here, we describe five infants with molecularly confirmed diagnoses of SHOX haploinsufficiency who presented in utero with short long bones during routine antenatal scanning from as early as 19 weeks gestation. Other foetal growth parameters were normal. The molecular basis of SHOX haploinsufficiency was distinct in each case. In four cases, SHOX haploinsufficiency was inherited from a previously undiagnosed parent. In our de novo case, SHOX haploinsufficiency reflected the formation of a derivative sex chromosome during paternal meiosis. Final adult height in the SHOX-deficient parents ranged from -1.9 to -1.2 SDS. All affected parents had disproportionately short limbs and two affected mothers had bilateral Madelung deformity. To our knowledge, SHOX haploinsufficiency has not previously been reported to present in utero. Our experience illustrates that SHOX deficiency should form part of the differential diagnosis of foetal short long bones and suggests a low threshold for genetic testing. This should be particularly targeted at, but not limited to, families with a history of features suggestive of SHOX deficiency. Data on the postnatal growth of our index cases is presented which demonstrates that antenatal presentation of SHOX haploinsufficiency is not indicative of severe postnatal growth restriction. Early identification of SHOX deficiency will enable accurate genetic counselling reflecting a good postnatal outcome and facilitate optimal initiation of growth hormone therapy.

Severe rhizomelic shortening in a child with a complex duplication/deletion rearrangement of chromosome X

Mesomelic and rhizo-mesomelic dysplasias are a group of disorders characterized by abnormal shortening of the limbs. One of the most common causes of mesomelic shortening is the loss of the transcription factor SHOX. In this clinical report, we present a patient who in addition to mesomelic shortening has severe rhizomelic shortening and developmental delay. Karyotyping revealed a recombinant X chromosome in which the region distal to Xp22.33 (where SHOX is found) was replaced with material from Xq28. Included in the region distal to Xq28 is the gene MECP2 and this patient presents with features of MECP2 duplication syndrome. We find that this patient has skeletal features not typical with the loss of SHOX that are likely explained by the rearrangement of the X chromosome. Further delineation of this rearrangement may allow for the identification of additional genetic mechanisms critical for the development of the limbs.

X-linked icthyosis and neurodevelopmental disorders: A case report and review of literature

The genetics of neurodevelopmental disorders have long intrigued clinicians and researchers alike. In this case report, we report a rare case of neurodevelopmental disorders associated with icthyosis with an underlying SHOX (short stature homeobox) gene mutation.

Biological mechanisms associated with increased perseveration and hyperactivity in a genetic mouse model of neurodevelopmental disorder

Chromosomal deletions at Xp22.3 appear to influence vulnerability to the neurodevelopmental disorders attention deficit hyperactivity disorder (ADHD) and autism. 39,X(Y*)O mice, which lack the murine orthologue of the Xp22.3 ADHD candidate gene STS (encoding steroid sulfatase), exhibit behavioural phenotypes relevant to such disorders (e.g. hyperactivity), elevated hippocampal serotonin (5-HT) levels, and reduced serum levels of dehydroepiandrosterone (DHEA). Here we initially show that 39,X(Y*)O mice are also deficient for the recently-characterised murine orthologue of the Xp22.3 autism candidate gene ASMT (encoding acetylserotonin-O-methyltransferase). Subsequently, to specify potential behavioural correlates of elevated hippocampal 5-HT arising due to the genetic lesion, we compared 39,X(Y*)O MF1 mice to 40,XY MF1 mice on behavioural tasks taxing hippocampal and/or 5-HT function (a 'foraging' task, an object-location task, and the 1-choice serial reaction time task of impulsivity). Although Sts/Asmt deficiency did not influence foraging behaviour, reactivity to familiar objects in novel locations, or 'ability to wait', it did result in markedly increased response rates; these rates correlated with hippocampal 5-HT levels and are likely to index behavioural perseveration, a frequent feature of neurodevelopmental disorders. Additionally, we show that whilst there was no systematic relationship between serum DHEA levels and hippocampal 5-HT levels across 39,X(Y*)O and 40,XY mice, there was a significant inverse linear correlation between serum DHEA levels and activity. Our data suggest that deficiency for genes within Xp22.3 could influence core behavioural features of neurodevelopmental disorders via dissociable effects on hippocampal neurochemistry and steroid hormone levels, and that the mediating neurobiological mechanisms may be investigated in the 39,X(Y*)O model.

Cognitive, behavioural and psychiatric phenotypes associated with steroid sulfatase deficiency

The enzyme steroid sulfatase (STS) desulfates a variety of steroid compounds thereby altering their activity. STS is expressed in the skin, and its deficiency in this tissue has been linked to the dermatological condition X-linked ichthyosis. STS is also highly expressed in the developing and adult human brain, and in a variety of steroidogenic organs (including the placenta and gonads); therefore it has the potential to influence brain development and function directly and/or indirectly (through influencing the hormonal milieu). In this review, we first discuss evidence from human and animal model studies suggesting that STS deficiency might predispose to neurobehavioural abnormalities and certain psychiatric disorders. We subsequently discuss potential mechanisms that may underlie these vulnerabilities. The data described herein have potential implications for understanding the complete spectrum of clinical phenotypes associated with X-linked ichthyosis, and may indicate novel pathogenic mechanisms underlying psychological dysfunction in developmental disorders such as attention deficit hyperactivity disorder and Turner syndrome.

A case of 9.7 Mb terminal Xp deletion including OA1 locus associated with contiguous gene syndrome

Terminal or interstitial deletions of Xp (Xp22.2→Xpter) in males have been recognized as a cause of contiguous gene syndromes showing variable association of apparently unrelated clinical manifestations such as Leri-Weill dyschondrosteosis (SHOX), chondrodysplasia punctata (CDPX1), mental retardation (NLGN4), ichthyosis (STS), Kallmann syndrome (KAL1), and ocular albinism (GPR143). Here we present a case of a 13.5 yr old boy and sister with a same terminal deletion of Xp22.2 resulting in the absence of genes from the telomere of Xp to GPR143 of Xp22. The boy manifested the findings of all of the disorders mentioned above. We began a testosterone enanthate monthly replacement therapy. His sister, 11 yr old, manifested only Leri-Weill dyschondrosteosis, and had engaged in growth hormone therapy for 3 yr. To the best of our knowledge, this is the first report of a male with a 9.7 Mb terminal Xp deletion including the OA1 locus in Korea.

ATRX in chromatin assembly and genome architecture during development and disease

The regulation of genome architecture is essential for a variety of fundamental cellular phenomena that underlie the complex orchestration of mammalian development. The ATP-dependent chromatin remodeling protein ATRX is emerging as a key regulatory component of nucleosomal dynamics and higher order chromatin conformation. Here we provide an overview of the role of ATRX at chromatin and during development, and discuss recent studies exposing a repertoire of ATRX functions at heterochromatin, in gene regulation, and during mitosis and meiosis. Exciting new progress on several fronts suggest that ATRX operates in histone variant deposition and in the modulation of higher order chromatin structure. Not surprisingly, dysfunction or absence of ATRX protein has devastating consequences on embryonic development and leads to human disease.

Familial X;Y translocation with distinct phenotypic consequences: Characterization using FISH and array CGH

X;Y translocation is a relatively rare event in humans. Analyzed cytogenetically, the majority of these aberrations have breakpoints at Xp22 and Yq11. Females with t(X;Y)(p22;q11) are phenotypically normal except for short stature, while the males may have abnormalities. Aberrations that lead to nullisomy of the deleted region and complete loss of the respective genes have been recognized as a cause of variable contiguous gene syndromes in males. The phenotype depends on the extent and position of the deletion showing the variable association of apparently unrelated clinical manifestations such as ichthyosis, chondrodysplasia punctata, hypogonadotropic hypogonadism with anosmia, ocular albinism, short stature, and mental retardation. In addition, some patients have been reported with symptoms of attention deficit hyperactivity disorder. The extent of terminal Xp deletions is limited by the presence of male lethal genes in Xp22.2 at about 10-11 Mb from the telomere. The deletions in the majority of viable reported male patients extend to the STS ( approximately 7.0 Mb) or to the KAL1 ( approximately 8.5 Mb) loci. We present a clinical, cytogenetic, FISH, and array CGH study of a family with an Xp;Yq translocation. The chromosomal status is also discussed in the light of their phenotypic traits. The final karyotypes of the patients were designated as: Patient 1: 46,Y,der(X),t(X;Y)(p22;q12).ish der(X)(Xpter-,DXZ1+,Xqter+)mat.arr cgh Xp22.31p22.33(RP11-60P14 --> RP13-391G2)x0;arr cgh Yq11.221qter (RP11-235I1 --> RP11-270H4)x2.Patient 2: 46,X,der(X),t(X;Y)(p22;q12).ish der(X)(Xpter-,DXZ1+,Xqter+)mat.arr cgh Xp22.31p22.33(RP11-60P14 --> RP13-391G2)x1;arr cgh Yq11.221qter (RP11-235I1 --> RP11-270H4)x1.

X-linked brachytelephalangic chondrodysplasia punctata: a simple trait that is not so simple

Brachytelephalangic chondrodysplasia punctata (CDPX1) is an X-linked recessive disorder caused by mutations in the arylsulfatase E (ARSE) gene, characterized by the presence of stippled epiphyses on radiograms in infancy and early childhood. Other features include hypoplasia of the midface and of the nasal bone, short stature, brachytelephalangy, and ectopic calcifications. Patients display marked clinical variability and there is no clear genotype-phenotype correlation. We report on a 14-month-old boy who presented with respiratory stridor due to tracheal calcifications. He had mild midface hypoplasia and brachytelephalangy, but lacked other features of CDPX1, such as short stature and epiphyseal stippling. Analysis of ARSE detected a deletion involving exons 7-10. His maternal grandfather harbored the same defect but lacked any clinical manifestation. These findings underscore two important points. First, the absence of stippled epiphyses on radiograms should not be considered an exclusion criteria for ARSE mutation screening in patients with other features of the disease, especially after the neonatal period. Second, counseling to parents of affected children should be cautious because although the theoretical risk of inheriting the ARSE mutation is 50% for every male child of a carrier mother, it is not possible to determine whether he will develop features of CDPX1 and the eventual severity of symptoms. The actual risk of developing the disease is probably lower than 50%. Conversely, normal prenatal sonography does not rule out potentially severe complications such as tracheal stenosis.

Steroid sulfatase deficiency and contiguous gene deletion syndrome amongst pregnant patients with low serum unconjugated estriols

OBJECTIVE

To ascertain all prenatally diagnosed cases of Steroid Sulfatase (STS) deficiency in British Columbia between August 2002 and July 2007 to determine the incidence of this condition, the clinical and laboratory findings, and the risk of a contiguous gene deletion syndrome.

METHODS

We reviewed the medical records of these patients to obtain detailed information about the maternal serum screening results, family history, investigations performed, and outcome of the pregnancy.

RESULTS

Thirty pregnant patients were found to have a male fetus/infant with STS deficiency, giving a minimal estimated incidence of this condition of approximately 1 in 1513 males. In twenty nine cases, this condition was isolated. One patient was found to have a contiguous gene deletion syndrome. In cases of sporadic STS deficiency diagnosed prenatally, the frequency of contiguous gene deletion syndrome in this study was 1 out of 12 (8.3%).

CONCLUSION

The clinical, cytogenetic and molecular data on this series of prenatally diagnosed cases of STS deficiency indicates that this is a common condition and in cases with no family history, the risk of contiguous gene deletion syndrome is significant, and warrants additional molecular genetic investigations of the mother and/or fetus.

The genetic overlap of attention deficit hyperactivity disorder and autistic spectrum disorder

Autistic spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) are classified as distinct disorders within the DSM-IV-TR (1994). The manual excludes simultaneous use of both diagnoses in case of overlap on a symptomatic level. However this does not always represent clinical observations and findings of previous studies. This review explores the genetic basis of the phenomenological overlap between ADHD and ASD. Based on an extensive review of twin-, linkage-, association studies, and reported structural genomic abnormalities associated with these disorders, we have identified seventeen regions on the human genome that can be related to both disorders. These regions of shared genetic association are: 2q35, 3p14, 4p16.1, 4p16.3, 5p15.31, 5p15.33, 7p12.3, 7p22, 7q21, 8q24.3, 14q12, 15q11–12, 16p13, 17q11, 18q21–23, 22q11.2, Xp22.3. The presented data are of interest for future genetic studies and appear to suggest the existence of a phenotype partition that may differ from the current classification of psychiatric disorders.

Girl with partial Turner syndrome and absence epilepsy

This report describes a 16-year-old girl with short stature (-5 standard deviations), normal puberty, panic attacks, absence epilepsy, some stigmata of Turner syndrome, and a Madelung deformity. Routine chromosomal analysis revealed a female karyotype with one abnormal chromosome X, with the suspicion of additional material on the short arm. With fluorescent in situ hybridization and array-multiplex amplifiable probe hybridization methodology, a complex aberration was detected, with a deletion of the distal part of Xp22.33 (including the short-stature homeobox gene) and a duplication of Xp22.32-p22.12 proximal to the deleted segment. The deletion in our patient involves the Xp22.33 region. Two genes in this region may contribute to the patient's phenotype: short-stature homeobox, and visuospatial/perceptual abilities. The duplication in our patient involves the Xp22.12-p22.32 region, which, according to the Online Mendelian Inheritance in Man database, contains at least 93 genes, 49 of which are of unknown function. It is difficult to conjecture which gene overexpression in this region may have contributed to the phenotype of our patient. To our knowledge, this small, complex chromosome X aberration was not described previously.

Normal intelligence and social interactions in a male patient despite the deletion of NLGN4X and the VCX genes

Xp22.3 deletion in males can be associated with short stature (SHOX), chondrodysplasia punctata (ARSE), mental retardation (MRX49 locus), ichthyosis (STS), Kallmann syndrome (KAL1) and ocular albinism (OA1), according to the size of the deletion. Studies of terminal and interstitial deletions in male patients with a partial nullisomy of the X chromosome have led to the identification of the VCX-3A gene at the MRX49 locus on Xp22.3. The NLGN4X gene has then been identified less than 350 kb away from VCX-3A. Nonsense mutations in NLGN4X have been associated with autism and/or moderate mental retardation in males. We report a 17-year old male patient presenting with severe ichthyosis and Kallmann syndrome related to a 3.7 Mb interstitial Xp22.3 deletion, encompassing STS and KAL1 genes, respectively. However, despite the deletion of NLGN4X and all VCX genes, including VCX-3A, our patient did not manifest any learning disabilities or behavioural problems. Therefore, our case argues against a major role of NLGN4X and the VCX genes alone in cognitive development and/or communication processes.

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.

Contiguous gene syndrome due to an interstitial deletion in Xp22.3 in a boy with ichthyosis, chondrodysplasia punctata, mental retardation and ADHD

Microdeletions of Xp22.3 can result in contiguous gene syndromes, showing the variable association of apparently unrelated clinical manifestations such as ichthyosis, chondrodysplasia punctata, hypogonadotropic hypogonadism, anosmia, ocular albinism, short stature and mental retardation. We report on a boy with ichthyosis, dysmorphic features and mental retardation with ADHD. The patient was born at term after a pregnancy complicated by threatened abortion; decreased fetal movements and low estriol serum levels were reported during the last trimester. The boy was referred to us at the age of 13 years. He presented with aggressive and hyperactive behavior. He had dry hair, a flat face, bilateral lens opacities, a small nose with hypoplastic tip, alae nasi and nares, a high-arched palate with a very small cleft, mixed dentition with 7 unerupted permanent teeth, left sensorineural and right mixed hearing loss with a calcified plaque of the tympanic membrane, marked shortness of terminal phalanges of hands and feet, ichthyosis of trunk and limbs. The genomic interval between AFM248th5 and KAL1 was investigated. PCR analysis showed a deletion in Xp22.3, with the distal breakpoint between the marker AFM248th5 and PABX and the proximal one between DXS278 and KAL1. Array-CGH and FISH analysis confirmed the interstitial deletion (of about 5.5 Mb) and refined the breakpoints. We discuss the phenotype of our patient in relationship to the deleted segment and the possibility of mental retardation and ADHD genes in the region.

Scope for more genetic testing in learning disability. Case report of an inherited duplication on the X-chromosome

There have been major advances in the past few years in our understanding of the X-linked learning disabilities. The most common of these is the fragile-X syndrome, but the number of other gene defects that are now recognised to be linked with learning disability is increasing year on year. We describe one family displaying a family displaying a rare X-linked abnormality. Repeat genetic testing was requested for a family member with mild learning disability when, following chromosomal analysis for her brother, it became known that he had a genetic defect. The genetic defect 46, Xdup(X) (p22.13 p22.31) was identified. To our knowledge this is the first time this precise configuration has been demonstrated. We conclude that genetic testing for individuals with learning disability is worthwhile, even when there may be only a low index of suspicion.

Subterminal deletion/duplication event in an affected male due to maternal X chromosome pericentric inversion

We report a 13-month-old male infant with an apparently normal karyotype, severe growth and developmental delay, ichthyosis, hypogonadism, limb shortness, hypoplasia of the corpus callosum and a round, flat face and thin upper lip as a consequence of a subtelomeric del/dup event of the X chromosome. The recombinant X chromosome (rec(X)), derived from crossing-over within the inversion, was identified in a family, in which the mother is a carrier of pericentric inversion of one X chromosome and pericentric inversion of the heterochromatic region of chromosome 9. The inv(X) chromosome was also analysed in her sister and daughter. The rec(X) had a duplication of the segment Xq27.3-->Xqter and deletion of the Xp22.31-->Xpter and was interpreted as Xqter-Xq27.3::Xp22.31-Xqter. The rec (X) was characterised by FISH using a number of BAC probes. There are only three published reports of chromosome rearrangements resulting in a similar subtelomeric duplication of Xq in males. The proband's phenotype corresponds to descriptions of contiguous gene syndromes due to deletion of the STS, SHOX, ARSE and KAL genes. Despite the loss of the ARSE gene there was no evidence of chondrodysplasia punctata. Additional conditions associated with duplication of the Xq28 segment, such as severe growth retardation and developmental delay, a peculiar head shape, atrophy of the cerebral hemispheres and hypoplasia of the cerebellum and corpus callosum, were observed.

CONCLUSION

Fluorescent in situ hybridisation techniques using subtelomeric DNA probes are essential tools for detection of such complex submicroscopic chromosomal rearrangements as the dup/del event of the X chromosome described in our patient.