Growth hormone deficiency and empty sella syndrome in a boy with dup(X) (q13.3----q21.2)

A novel de novo partial xq duplication in a girl with short stature, nonverbal learning disability and diminished ovarian reserve - effect of growth hormone treatment and fertility preservation strategies: a case report and up-to-date review

Background

Xq duplication is a rare condition with a very variable phenotype, which could mimic other genetic syndromes involving the long arm of chromosome X. Sometimes short stature and diminished ovarian reserve (DOR) may be present. Treatments with rGH (Recombinant growth Hormon) or with fertility preservation strategies have not been previously described.

Case presentation

We present the case of a female with a novel de novo Xq partial duplication (karyotype: 46,Xder(X)(qter→q21.31::pter→qter) confirmed by array-CGH analysis. She presented with short stature, Nonverbal Learning Disability, developmental delay during childhood, severe scoliosis, spontaneous onset of menarche and irregular menstrual cycles. AMH (Anti-Müllerian Hormone) allowed detection of a preserved but severely diminished ovarian reserve with a POI (Premature Ovarian insufficiency) onset risk. She was effectively subjected to fertility preservation strategies and rGH therapy. We also reviewed other published cases with Xq duplication, reporting the main clinics characteristics and any adopted treatment.

Conclusions

rGH treatment and cryopreservation in a multidisciplinary approach are good therapeutic strategies for Xq duplication syndrome with short stature and premature ovarian failure.

Molecular genetic characterization of a prenatally detected 1.484-Mb Xq13.3-q21.1 duplication encompassing ATRX and a literature review of syndromic intellectual disability and congenital abnormalities in males with a duplication at Xq13.3-q21.1

OBJECTIVE

We present prenatal diagnosis of dup(X)(q13.3q21.1) in a male fetus and molecular genetic analysis in three generations and a literature review of syndromic intellectual disability and congenital abnormalities in males with a duplication at Xq13.3-q21.1.

CASE REPORT

A 35-year-old, primigravid woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. The woman and her mother were phenotypically normal, and there was no intellectual disability in the maternal family. Cytogenetic analysis of cultured amniocytes revealed a karyotype of 46,XY. Simultaneous array comparative genomic hybridization (aCGH) analysis on uncultured amniotic fluid incidentally detected a 1.484-Mb microduplication of Xq13.3-q21.1 encompassing ATRX. Subsequent aCGH analysis on fetal blood, maternal blood and grandmother's blood revealed the same 1.484-Mb dup(X)(q13.3q21.1). Prenatal ultrasound findings were unremarkable with no growth restriction and no short stature. After genetic counseling of syndromic intellectual disability in males with ATRX duplication, the woman elected to terminate the pregnancy. The fetus postnatally manifested hypoplastic male external genitalia, clinodactyly, hypertelorism, midface hypoplasia, epicanthic folds and micrognathia.

CONCLUSION

Simultaneous aCGH analysis on uncultured amniotic fluid in addition to conventional cytogenetics at amniocentesis is practical and may help in detecting unknown familial inheritance of subtle X chromosome aberrations.

Inherited Xq13.2-q21.31 duplication in a boy with recurrent seizures and pubertal gynecomastia: Clinical, chromosomal and aCGH characterization

We report on a 16-year-old boy with a maternally inherited ~ 18.3 Mb Xq13.2-q21.31 duplication delimited by aCGH. As previously described in patients with similar duplications, his clinical features included intellectual disability, developmental delay, speech delay, generalized hypotonia, infantile feeding difficulties, self-injurious behavior, short stature and endocrine problems. As additional findings, he presented recurrent seizures and pubertal gynecomastia. His mother was phenotypically normal and had completely skewed inactivation of the duplicated X chromosome, as most female carriers of such duplications. Five previously reported patients with partial Xq duplications presented duplication breakpoints similar to those of our patient. One of them, a fetus with multiple congenital abnormalities, had the same cytogenetic duplication breakpoint. Three of the reported patients shared many features with our proband but the other had some clinical features of the Prader-Willi syndrome. It was suggested that ATRX overexpression could be involved in the major clinical features of patients with partial Xq duplications. We propose that this gene could also be involved with the obesity of the patient with the Prader-Willi-like phenotype. Additionally, we suggest that the PCDH11X gene could be a candidate for our patient's recurrent seizures. In males, the Xq13-q21 duplication should be considered in the differential diagnosis of Prader-Willi syndrome, as previously suggested, and neuromuscular diseases, particularly mitochondriopathies.

A 5.8 Mb interstitial deletion on chromosome Xq21.1 in a boy with intellectual disability, cleft palate, hearing impairment and combined growth hormone deficiency

Background

Deletions of the long arm of chromosome X in males are a rare cause of X-linked intellectual disability. Here we describe a patient with an interstitial deletion of the Xq21.1 chromosome.

Case presentation

In a 15 year boy, showing intellectual disability, short stature, hearing loss and dysmorphic facial features, a deletion at Xq21.1 was identified by array-CGH. This maternally inherited 5.8 Mb rearrangement encompasses 14 genes, including BRWD3 (involved in X-linked intellectual disability), TBX22 (a gene whose alterations have been related to the presence of cleft palate), POU3F4 (mutated in X-linked deafness) and ITM2A (a gene involved in cartilage development).

Conclusion

Correlation between the clinical findings and the function of gene mapping within the deleted region confirms the causative role of this microrearrangement in our patient and provides new insight into a gene possibly involved in short stature.

Trisomy Xp and partial tetrasomy Xq resulting from gain of a rearranged X chromosome in a female fetus: pathogenic or not?

Cytogenetic analysis of chorionic villous sampling revealed a mosaic karyotype with gain of a rearranged X chromosome. Microarray and additional studies indicated that the rearranged X carried an inverted duplication, a deletion and a satellited Xqter. Gain of this rearranged X was confirmed by follow-up amniocentesis and postnatal cord blood sample. A full-term infant girl was delivered and showed normal physical findings at both birth and 21-month follow-up examinations. Late replication studies demonstrated that the rearranged X was inactivated in all abnormal cells analyzed. Skewed X-inactivation may suppress the potentially deleterious effects of genomic imbalance; however, gain of X chromosomes, particularly rearranged X chromosomes, often presents challenges for prenatal genetic counseling. The gradation of clinical phenotype severity generally correlates with the number of additional X chromosomes. However, the X chromosome regions responsible for the abnormal phenotypes are poorly understood. This case will further elucidate the phenotypic effects of X inactivation and X chromosome abnormalities.

A case report of two male siblings with autism and duplication of Xq13-q21, a region including three genes predisposing for autism

Autism spectrum disorder, severe behaviour problems and duplication of the Xq12 to Xq13 region have recently been described in three male relatives. To describe the psychiatric comorbidity and dysmorphic features, including craniosynostosis, of two male siblings with autism and duplication of the Xq13 to Xq21 region, and attempt to narrow down the number of duplicated genes proposed to be leading to global developmental delay and autism. We performed DNA sequencing of certain exons of the TWIST1 gene, the FGFR2 gene and the FGFR3 gene. We also performed microarray analysis of the DNA. In addition to autism, the two male siblings exhibited severe learning disability, self-injurious behaviour, temper tantrums and hyperactivity, and had no communicative language. Chromosomal analyses were normal. Neither of the two siblings showed mutations of the sequenced exons known to produce craniosynostosis. The microarray analysis detected an extra copy of a region on the long arm of chromosome X, chromosome band Xq13.1-q21.1. Comparison of our two cases with previously described patients allowed us to identify three genes predisposing for autism in the duplicated chromosomal region. Sagittal craniosynostosis is also a new finding linked to the duplication.

Familial interstitial Xq27.3q28 duplication encompassing the FMR1 gene but not the MECP2 gene causes a new syndromic mental retardation condition

X-linked mental retardation is a common disorder that accounts for 5-10% of cases of mental retardation in males. Fragile X syndrome is the most common form resulting from a loss of expression of the FMR1 gene. On the other hand, partial duplication of the long arm of the X chromosome is uncommon. It leads to functional disomy of the corresponding genes and has been reported in several cases of mental retardation in males. In this study, we report on the clinical and genetic characterization of a new X-linked mental retardation syndrome characterized by short stature, hypogonadism and facial dysmorphism, and show that this syndrome is caused by a small Xq27.3q28 interstitial duplication encompassing the FMR1 gene. This family broadens the phenotypic spectrum of FMR1 anomalies in an unexpected manner, and we suggest that this condition may represent the fragile X syndrome "contre-type".

Xq13.2q21.1 duplication encompassing the ATRX gene in a man with mental retardation, minor facial and genital anomalies, short stature and broad thorax

In a man with severe mental retardation, minor facial and genital anomalies, disproportionate short stature and a broad thorax, we identified a de novo Xq13.2q21.1 duplication by array CGH. This 7 Mb duplication encompasses 23 known genes, including the X-linked mental retardation (XLMR) genes ATRX and SLC16A2. The phenotype of this patient is similar to that described in more than 10 previously reported patients with overlapping Xq duplications. Detailed comparison of the clinical characteristics and the function of the genes located in the commonly duplicated regions of these patients led us to the hypothesis that an increased dosage of ATRX and perhaps of other genes is involved in the pathogenetic mechanism of this XLMR phenotype, including mental retardation, short stature, and genital abnormalities comprising cryptorchidism and/or a small penis.

Two Patients with X Chromosome Duplication: dupXp and dupXq

Structural abnormalities of the X chromosome may lead to different phenotypes, depending on the chromosome region affected. We report phenotypic findings of two patients who had X chromosome duplications. One had a menstrual irregularity, a low hairline, cubitus valgus and suffered from dyslexia. The other had multiple congenital anomalies, severe mental-motor retardation and intractable epilepsy. The karyotypes were 46,X,dup(X) (p11.3p21) and 46,X,dup(X)(q13q25) respectively.

Prader-Willi syndrome phenocopy due to duplication of Xq21.1-q21.31, with array CGH of the critical region

We report on a 4-year-old male with an interstitial tandem duplication of Xq21.1-q21.31 who presented with clinical features of Prader-Willi syndrome (PWS). The duplication was maternally inherited. Abnormalities of the X chromosome have previously been reported in association with a PWS phenotype, but to date, specific duplications of Xq21.1-q21.31 have not. We refined the chromosomal breakpoints seen on initial G-banded karyotyping in our case with comparative genomic hybridization by microarray (array CGH). The duplication was between 11.1 and 14.4 Mb in length and overlaps with three loci to which mental retardation with PWS-like features have been previously mapped, showing the utility of array CGH in helping to identify candidate genes. We conclude that duplication of chromosomal region Xq21.1-q21.31 potentially results in a PWS-like phenotype. Reviewing the literature on similar duplications, we further conclude that distal Xq duplications can result in features typically seen in infants with PWS, while proximal duplications can result in features typically seen in older children and adults with PWS. Duplications of chromosome Xq should be considered in the differential diagnosis of PWS, especially in males.

Isolated growth hormone deficiency

Isolated growth hormone deficiency (IGHD) represents conditions of GH deficiency that are not necessarily associated with other pituitary hormone deficiencies or with an organic lesion. Three sub-categories of IGHD have been clinically identified (IGHD types 1-3), and IGHD type 1 has been further separated into IGHD types 1a and b. However, this clinical sub-categorization of IGHD may need reconsideration due to the recent identification of molecular heterogeneity within each sub-type of IGHD. In a small number of children with IGHD, defects in the GH, GH-releasing hormone receptor (GHRH-R), and GH1 genes have been identified. In most cases, no cause for IGHD can be identified; however, the proportion of idiopathic IGHD cases may be decreasing due to identification of causative factors. The phenotype of IGHD is variable depending in part on the underlying genetic disorders in the affected individuals. Several studies have focused on the usefulness of MRI findings in patients with GHD but anatomic abnormalities of the pituitary gland are variable. We review current studies and the clinical, biochemical, and molecular features described for different groups of affected individuals with IGHD.

Xq chromosome duplication in males: Clinical, cytogenetic and array CGH characterization of a new case and review

Males with duplications within the long arm of the X chromosome are rare and most cases are inherited from a maternal heterozygote. We report a male with a de novo Xq duplication and review of the literature. The proband was ascertained prenatally after an abnormal expanded alpha-fetoprotein (AFP) screen and abnormal ultrasound findings. Chromosome analysis on amniocyte and subsequent peripheral blood lymphocyte cultures showed a male karyotype containing additional material on the long arm of the X chromosome. Fluorescence in situ hybridization with an X chromosome whole chromosome paint probe showed that the additional material was derived from the X chromosome, interpreted as a dup(X)(q13.3q24). Further characterization of the duplication by array CGH showed a duplication size between 30-44 Mb as determined by the map position of the flanking clones on the array, and refined the breakpoints of the duplicated region to Xq21.32 --> Xq25. At birth, the proband had multiple craniofacial abnormalities, musculoskeletal anomalies, bilateral cryptorchidism with scrotal hypoplasia, conductive hearing loss, and profound generalized hypotonia despite normal birthweight, length, and head circumference. Although data regarding Xq duplications in males are limited, a clear pattern of characteristic features can be discerned as illustrated in the present case and confirmed in our literature review. Mental, psychomotor and growth retardation, as well as, craniofacial anomalies, muscle hypotonia, hypoplastic genitalia, cryptorchidism, feeding difficulties, and endocrine dysfunction are all significant issues in these individuals.

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.

Inv(X)(p21.1;q22.1) in a man with mental retardation, short stature, general muscle wasting, and facial dysmorphism: clinical study and mutation analysis of the NXF5 gene

We describe a 59-year-old male (patient A059) with moderate to severe mental retardation (MR) and a pericentric inversion of the X-chromosome: inv(X)(p21.1;q22.1). He had short stature, pectus excavatum, general muscle wasting, and facial dysmorphism. Until now, no other patients with similar clinical features have been described in the literature. Molecular analysis of both breakpoints led to the identification of a novel "Nuclear RNA export factor" (NXF) gene cluster on Xq22.1. Within this cluster, the NXF5 gene was interrupted with subsequent loss of gene expression. Hence, mutation analysis of the NXF5 and its neighboring homologue, the NXF2 gene was performed in 45 men with various forms of syndromic X-linked MR (XLMR) and in 70 patients with nonspecific XLMR. In the NXF5 gene four nucleotide changes: one intronic, two silent, and one missense (K23E), were identified. In the NXF2 gene two changes (one intronic and one silent) were found. Although none of these changes were causative mutations, we propose that NXF5 is a good candidate gene for this syndromic form of XLMR, given the suspected role of NXF proteins is within mRNA export/transport in neurons. Therefore, mutation screening of the NXF gene family in phenotypically identical patients is recommended.

Functional disomy for Xq26.3-qter in a boy with an unbalanced t(X;21)(q26.3;p11.2) translocation

A nine-month-old boy, with functional disomy for Xq26-qter and multiple congenital abnormalities, is reported. The boy had severe pre- and postnatal growth retardation, profound developmental delay, hypotonia, microcephaly, agenesis of the corpus callosum, dysmorphic facial features, cryptorchidism, and left multidysplastic kidney. He developed feeding difficulties and infantile spasms. G-banding analysis of his chromosomes showed additional material on the short arm of chromosome 21. His parents refused to submit to chromosome analysis. Analysis with chromosome microdissection followed by reverse and forward chromosome painting indicated his karyotype as 46,XY,der(21)t(X;21)(q26;p11.2). This is the first description of pure functional disomy for Xq26-qter due to an unbalanced X-autosome translocation.

Empty sella syndrome: does it exist in children?

OBJECT

The empty sella syndrome (ESS) is well documented in adults, and although the same phenomenon of herniation of the arachnoid space into the enlarged sella turcica has been noted in children, it is not widely known that children suffer from this syndrome. Therefore, the aims of this paper are to increase neurosurgeons' awareness of the existence of this phenomenon in children and to add to the scant body of literature on the subject.

METHODS

The authors treated 12 children, ranging in age between 2 and 8 years, in whom neuroradiological studies demonstrated an enlarged sella turcica filled with cerebrospinal fluid and herniation of suprasellar and arachnoid spaces. The causes of ESS in these children were high intracranial pressure, neglected or improperly treated hydrocephalus, and suprasellar arachnoid cyst. Primary ESS was found as well. Most of the children presented with headache, abnormal body weight (the majority being underweight), and short stature. The results of hormone assays were normal in all children.

CONCLUSIONS

If undiagnosed and untreated, ESS in children may lead to serious consequences, including impairment of pituitary and hypothalamic function and damage to the optic chiasm. It is important to raise awareness in the neurosurgical community about the existence of ESS in children so that it can be diagnosed and treated at an early stage. A classification system for the diaphragma sellae is recapitulated.

Inherited inverted duplication of X chromosome in a male: report of a patient and review of the literature

Nineteen cases of duplication of segments of the long arm of chromosome X have been published in 13 males and in 6 females. We report an additional case of a male with growth and mental retardation, growth hormone deficiency, compensated primary hypothyroidism, distinctive anomalies of the face, hypoplastic genitalia, and hypotonia in whom inverted duplication of a segment in the long arm of X chromosome was diagnosed, 46,Y, dup (X)(q21.2q13.3), and mosaicism was demonstrated in his mother's X chromosome. The rearranged segment was diagnosed utilizing high resolution G-band technique and FISH studies, using chromosome X total chromosome probe and DNA XIST probe. This appears to be the first report of a patient with duplication of Xq and hypothyroidism.

Molecular cytogenetic identification of four X chromosome duplications

Four cases with previously unidentified X-chromosome abnormalities were studied by standard cytogenetic techniques and FISH in order to demonstrate the origin of the extra segment on the abnormal X chromosomes. All cases were identified as X-chromosome duplications by using a chromosome-specific painting probe. Application of appropriate locus-specific DNA probes as an adjunct to GTG- and RBG-banding proved useful in defining the breakpoints and the extent of the duplications. Although the duplicated X chromosome in female cases was selectively inactivated, as demonstrated by its late-replicating pattern, abnormal clinical findings were manifested in 3 female patients.

Two brothers with multiple congenital anomalies and mental retardation due to disomy (X)(q12-->q13.3) inherited from the mother

We present the phenotypic, cytogenetic and molecular findings in two dysmorphic and mentally retarded brothers with disomy Xq12-->q13.3. The mother and the grandmother carry the same rearrangement of the X chromosome, which was interpreted as an inverted insertion of the segment (X)(q12-->q13.3) into Xq21.2. The X-inactivation-specific-transcript (XIST) is expressed in the probands mother but is absent in her son, confirming the hypothesis that X inactivation is realized only if two X inactivation centers reside on different X-chromosomes (trans-configuration). In the phenotypically normal mother the aberrant X chromosome was late replicating in all cells, indicating functional monosomy of the constitutional segment trisomy. The phenotype of the brothers is considered to be the consequence of a functional disomy Xq12-->q13.3. The trait combination observed in the brothers was compared with the spectrum of clinical and anthropological traits for proximal Xq disomy in males, elaborated by phenotype analyses of the available literature cases.

Familial X-linked mental retardation and isolated growth hormone deficiency: clinical and molecular findings

We report on several members of a family with varying degrees of X-linked mental retardation (XLMR), isolated growth hormone deficiency (IGHD), and infantile behaviour but without other consistent phenotypic abnormalities. Male patients continued to grow until well into their twenties and reached a height ranging from 135 to 159 cm. Except one, all female carriers were mentally normal; their adult height ranged from 159 to 168 cm. By linkage studies we have assigned the underlying genetic defect to the Xq24-q27.3 region, with a maximum lod score of Z = 3.26 at theta = 0.0 for the DXS294 locus. The XLMR-IGHD phenotype in these patients may be due to pleiotropic effects of a single gene or it may represent a contiguous gene syndrome.

Localisation of two candidate genes for mental retardation using a YAC physical map of the Xq21.1-21.2 subbands

Genetic studies in families with X linked mental retardation have suggested the location of several MR genes in the human q21 region. Since the establishment of cloned resources is an essential step towards the cloning of genes involved in inherited diseases, we built a yeast artificial chromosome (YAC) contig and an STS map of this part of the X chromosome. The contig, which extends from PGK1 in Xq13.3 to DXS1002 in Xq21.2, consists of 30 YACs mapped with 21 markers and spans about 6 Mb. The YAC contig was used as a framework to localise several previously known genes and CEPH/Genethon polymorphic markers, as well as to construct a physical map of the region surrounding one of these genes. We recently localised a presumed MR locus to the region flanked by DXS233 (proximal) and CHM (distal). In the present work, the zinc finger gene, ZNF6, has been shown to lie within this region and to be highly expressed in brain, making it a good candidate MR gene. Similarly the VDAC1 gene has been mapped between DXS986 and DXS72 and its candidate gene status for the Allan-Herndon-Dudley syndrome is discussed.

A familial Xp+ chromosome, dup (Xq26.3-->qter)

A maternally transmitted Xp+ chromosome was associated with an abnormal phenotype, including developmental delay and short stature, in two male cousins and their 12 year old aunt. The respective mothers were not mentally impaired but had short stature. The G banding pattern identified the extra chromosome segment as a repeat of Xq26.3-->qter attached to an apparently intact Xp22.3 sub-band, so the Xp+ chromosome may be described as rea(X)(Xqter-->p22.3::Xq26.3-->Xqter). The rearranged chromosome was late replicating in 97 to 100% of the metaphases in the mothers but it was early replicating in 43% of the lymphocytes in the mentally defective female (n = 100 cells/subject). Fluorescence in situ hybridisation using X and Y chromosome paints, as well as cosmids A and 1A1 specific for loci within Xq28, confirmed both the identity of the extra segment and the entirety of the Xp pseudoautosomal region. Therefore, the phenotypic consequences in this family can be related to the Xq26.3-->qter functional disomy allowing for the effects of X inactivation in the female carriers.

The molecular pathology of pituitary hormone deficiency and resistance

In this chapter, we have reviewed the fast-moving area of the molecular pathology of pituitary hormone deficiencies and resistance. Examples have been described affecting all levels of pituitary function, i.e. the releasing hormone, its receptor, the pituitary hormone and its receptor, and the development of the pituitary gland. Other examples in these genes, and in those in which no mutation has yet been found, will undoubtedly be discovered in the next few years, throwing light on the structural basis of the gene product's function and allowing a greater understanding of endocrine physiology and pathophysiology. The main reason for this rapid progress in knowledge is the recent technological advances in mutation detection, which bring this activity within the grasp of the majority of reasonably equipped laboratories. Technological advancement, however is not all that it takes to carry out this work. The conditions caused by genetic damage such as we have described are rare, and there is clearly a requirement for great awareness on the part of the clinical endocrinologist. Patients in whom it is suspected that mutations such as these may occur require careful clinical and biochemical work-up. Indeed, in many instances, careful thought has to go into deciding what the phenotype of a particular mutation might be. Thus, the requirement for close collaboration between clinical and molecular endocrinologists has to be the important message for the future in this area of research.

Dir dup(X) (q13-->qter) in a girl with growth retardation, microcephaly, developmental delay, seizures, and minor anomalies

In males, duplication of a portion of Xq is associated with multiple congenital anomalies and developmental delay. Most females recognized as having dup(Xq) are phenotypically apparently normal relatives of phenotypically abnormal males; phenotypic normalcy has been attributed to selective inactivation of the duplicated X chromosome. Heretofore, apparently only 5 distinctly phenotypically abnormal females with dup(Xq) have been reported. We report on a 3-year-old girl with developmental delay, growth retardation, microcephaly, minor anomalies, and a seizure disorder who had a nonmosaic, de novo direct duplication of the terminal portion of one X chromosome. In each of 50 lymphocytes examined, the duplicated X chromosome was found to be late-replicating. This case shows that selective inactivation (as reflected by late replication) of the duplicated X chromosome does not inevitably confer phenotypic normalcy on females with dup(Xq), and suggests that other mechanisms must account for the phenotypic differences observed among females with dup(Xq), such as expression of recessive genes on the active X chromosome, incomplete inactivation of some portion of the duplicated chromosomal segment, an imprinting effect, or some combination of these.