Tandem duplication dup(X)(q13q22) in a male proband inherited from the mother showing mosaicism of X-inactivation

Clinical findings and a DNA methylation signature in kindreds with alterations in ZNF711

ZNF711 is one of eleven zinc-finger genes on the X chromosome that have been associated with X-linked intellectual disability. This association is confirmed by the clinical findings in 20 new cases in addition to 11 cases previously reported. No consistent growth aberrations, craniofacial dysmorphology, malformations or neurologic findings are associated with alterations in ZNF711. The intellectual disability is typically mild and coexisting autism occurs in half of the cases. Carrier females show no manifestations. A ZNF711-specific methylation signature has been identified which can assist in identifying new cases and in confirming the pathogenicity of variants in the gene.

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.

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.

De novo duplication of Xq22.1→q24 with a disruption of the NXF gene cluster in a mentally retarded woman with short stature and premature ovarian failure

OBJECTIVE

To present molecular cytogenetic characterization of a de novo duplication of Xq22.1→q24 in a mentally retarded woman with short stature and premature ovarian failure.

MATERIALS AND METHODS

A 19-year-old woman presented with psychomotor retardation, developmental delay, mental retardation, short stature, low body weight, general muscle hypotonia, distal muscle hypotrophy of the lower extremities, elongated digits, scanty pubic and axillary hair, hypoplastic external female genitalia, and secondary amenorrhea but no clinical features of Pelizaeus-Merzbacher disease. Conventional cytogenetic analysis revealed a karyotype of 46,X,dup(X)(q22.1q24). Fluorescence in situ hybridization determined a direct duplication with a linear tandem orientation. Array comparative genomic hybridization demonstrated partial trisomy Xq [arr cgh Xq22.1q24 (101,490,234-119,070,188 bp)×3] with a 17.6-Mb duplication.

RESULTS

The duplicated region contained NXF2B, NXF4, NXF3, PLP1, and PGRMC1 genes. There was a disruption of the NXF gene cluster of Xcen-NXF5-NXF2-NXF2B-NXF4-NXF3-Xqter.

CONCLUSION

A duplication of Xq22.1→q24 with a disruption of the NXF gene cluster in female patients can be associated with clinical manifestations of mental retardation in addition to short stature and premature ovarian failure.

Xq26.2-q26.3 microduplication in two brothers with intellectual disabilities: clinical and molecular characterization

Partial duplications involving the long arm of the X chromosome are associated with mental retardation, short stature, microcephaly, hypopituitarism and a wide range of physical findings. We identified an inherited Xq26.2-Xq26.3 duplication in two brothers with severe mental retardation, hypotonia, growth delay, craniofacial disproportion and dental malocclusion. Chromosome analysis was normal and multiplex ligation-dependent probe amplification analysis detected duplication on Xq26. Further characterization by array comparative genomic hybridization and quantitative PCR helped to determine proximal and distal duplication breakpoints giving a size of approximately 2.8 Mb. The duplication encompasses 24 known genes, including the X-linked mental retardation genes ARHGEF6, PHF6, HPRT1 and SLC9A6. Clinical and molecular characterization of Xq duplications will shed more light into the phenotypic implication of functional disomy of X-chromosome genes.

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.

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.

Functional disomy for Xq22-q23 in a girl with complex rearrangements of chromosomes 3 and X

A 5-year-old girl with developmental and growth retardation is reported with complex chromosome rearrangements consisting of a partial Xq deletion and an abnormal chromosome 3 with multiple breakpoints. GTG-banding, and multiplex and conventional FISH studies showed that a 6.6-Mb Xq22-q23 segment was inserted into 3q, in addition to three intrachromosomal insertions in chromosome 3. Her karyotype was thus interpreted as 46,X,der(X)(Xpter-->Xq22::Xq23-->Xqter),der(3)(3pter-->3p26::3p12-->3q25.3::3p12-->3p26::Xq22-->Xq23::3q25.3-->3qter). Replication R-banding study showed that the der(X) was inactivated in all blood lymphocytes analyzed. Methylation-specific PCR at the androgen receptor gene (HUMARA) locus at Xq11-q12 showed a skewed inactivation pattern with the active/inactive X chromosome ratio of 92/8. These data indicated the presence, in the majority of cells, of a functioning Xq22-q23 segment in both the normal X and the der(3) chromosomes. Her growth retardation, developmental delay, and other minor anomalies were most likely caused by dosage effects of the genes in the functionally disomic Xq22-q23 region. Despite the presence of two active copies of the proteolipid protein 1 gene (PLP1), she did not show the symptoms of Pelizaeus-Merzbacher disease, a subset of which has been known to be caused by the duplication of PLP1.

De novo dup(X)(q22.3q26) in a girl with evidence that functional disomy of X material is the cause of her abnormal phenotype

The relationship between phenotype and Xq duplications in females remains unclear. Some females are normal; some have short stature; and others have features such as microcephaly, developmental delay/mental retardation, body asymmetries, and gonadal dysgenesis. There are several hypotheses proposed in the literature to explain this variability. We describe a 7-year-old girl with dup(X)(q22.3q26). The pregnancy was complicated by intrauterine growth retardation, and she was distressed during labor. During her first year she fed poorly and failed to thrive. She has microcephaly, her height is at the 10th centile, and her hands and feet are strikingly small. She is hypotonic and delayed. Asymmetries of muscle power, and of leg and foot length have been noted. She has mild unilateral ptosis. She has some features of Turner syndrome, and multiple other minor anomalies such as flat labia. These are features common to other described females. This report describes our patient in detail and compares her phenotype to those of the other females with Xq duplications, displays our laboratory investigations, and discusses ideas regarding the pathogenesis of phenotype. The duplicated X is of paternal origin. It is inactivated in all cells; however, the distal duplicated portion appears to be active. We suggest that functional disomy of the duplicated X material, due to local escape from inactivation, may be responsible for the phenotype in the affected females.

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.

Hypomelanosis of Ito and X;autosome translocations: a unifying hypothesis

Hypomelanosis of Ito is a sporadic multisystem disorder known to be associated in many cases with chromosomal mosaicism. While no particular pattern is generally evident for the specific chromosomes involved in such patients, a subgroup of female patients exists in whom the common factor is the presence of a balanced, constitutional X;autosome translocation, with a cytogenetic breakpoint in the pericentromeric region of the X. It is argued here that the phenotype in these cases results not from the interruption of X linked genes but from the presence of mosaic functional disomy of X sequences above the breakpoint.

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.

Sex reversal in a child with a 46,X,Yp+ karyotype: support for the existence of a gene(s), located in distal Xp, involved in testis formation

We report on a sex reversed Japanese child with a 46,X,Yp+ karyotype, minor dysmorphic features, and no testicular development. The Yp+ chromosome was derived by translocation of an Xp fragment (Xp21-Xp22.3) to Yp11.3. This has resulted in deletion of distal part of the Y chromosome pseudoautosomal region (DXYS15-telomere) and duplication of the X specific region (DXS84-PABX) and proximal part of the pseudoautosomal region (MIC2-DXYS17). No deletion of the Y specific region was detected nor was any mutation found in SRY. Cytogenetic analysis suggests that the proximal part of the Xp fragment is the most distal part of the short arm of the Yp+ chromosome (Xp21----Xp 22.3::Yp11.3----Yqter). No chromosomal mosaicism was detected. These results are similar to previous reports of sex reversal in four subjects with a 46,Y,Xp+ karyotype. We conclude that the sex reversal is a direct, or indirect, consequence of having two active copies of the distal part of Xp and may indicate the presence of a gene(s) which acts in the testis determination or differentiation pathway.

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

A 2 8/12-year-old boy with severe growth failure and mental retardation was found to have a maternally derived tandem duplication of the long arm of X chromosome, dup(X) (q13.3----q21.2). Karyotypic interpretation was further confirmed in this patient by a double gene dose for red blood cell phosphoglycerate kinase. DNA replication study showed that the duplicated X chromosome was always late replicating in peripheral blood lymphocytes as well as in skin fibroblasts from the mother. Endocrine studies in the patient demonstrated growth hormone deficiency. Magnetic resonance imaging of the head then disclosed the empty sella syndrome. This appears to be the first report of a dup(Xq) patient associated with a growth hormone deficiency and the empty sella syndrome. We emphasize that duplication of the proximal Xq in males represents another microduplication syndrome (Thode-Leonard syndrome).

Physical mapping of an Xq-proximal interstitial duplication in a male

A viable duplication in the proximal long arm of the X chromosome in a boy with a malformative syndrome was delineated with molecular biology techniques using 14 probes from the X cen-Xq21 region. This analysis allowed us to refine the physical map of the X cen-Xq13 region.

A new syndrome with mental retardation, short stature and an Xq duplication

We describe a new X-linked syndrome of marked short stature, severe intellectual handicap and an unusual facial appearance. High resolution prometaphase banding showed affected males to have an X chromosome tandem duplication; their karyotypes were designated 46,dup(X) (q13.1-q21.1)Y. In carrier females the abnormal X chromosome was late replicating. To verify the duplication, gene dosage studies were performed using an enzyme assay and DNA techniques. Prenatal diagnosis is available for carrier females using chromosome analysis of amniocytes or chorionic villi.

45X/46X,r(X) with syndactyly and severe mental retardation

Two white females, age 2 1/2 and 33 years, respectively, were investigated because of severe mental retardation associated with neurologic abnormalities, coarse face, and soft tissue syndactyly involving upper and lower limbs. Each had cytogenetic findings of a mosaic variant of Ullrich-Turner syndrome with X ring chromosome in peripheral lymphocyte and skin fibroblasts. Early X replication occurred in one-third of the X ring chromosomes; there was no evidence for X-autosome translocation involving either X and an autosomal duplication; results of studies for fragility of the X chromosomes were unremarkable. In situ hybridization with an X centromere probe was positive for the ring. To our knowledge, the unusual constellation of cytogenetic, physical, and mental findings seen in these 2 individuals has not been reported previously.

An interstitial duplication of the X chromosome in a male allows physical fine mapping of probes from the Xq13-q22 region

An insertional translocation into the proximal long arm of the X chromosome in a boy showing muscular hypotony, growth retardation, psychomotor retardation, cryptorchidism, and Pelizaeus-Merzbacher disease (PMD) was identified as a duplication of the Xq21-q22 segment by employing DNA probes. With densitometric scanning for quantitation of hybridization signals, 15 Xq probes were assigned to the duplicated region. Analysis of the duplication allowed us to dissect the X-Y homologous region physically at Xq21 and to refine the assignments of the loci for DXYS5, DXYS12, DXYS13, DXS94, DXS95, DXS96, DXS111, and DXS211. Furthermore, we demonstrated the presence of two different DXYS13 and DXS17 alleles in genomic DNA of our patient, suggesting that the duplication resulted from a meiotic recombination event involving the two maternal X chromosomes.

Lipophilin (PLP) gene in X-linked myelin disorders

There are several X-linked diseases in animals and at least one in man in which there is a failure of CNS myelination. We have recently cloned cDNAs for lipophilin (PLP) with which PLP sequences were localized to a region of the long arm of the X chromosome (Xq13-q22 in man) close to the jimpy (jp) locus in that mouse mutant. The present communication pursues the postulate that some of this class of diseases may involve mutations at the PLP locus. Blot hybridization analysis of PLP mRNA levels revealed a five-to tenfold reduction in the brains of hemizygous jp/Y mice. The major PLP mRNA species of those mice was also reduced in size. However, Southern blots of jp DNA digested with many different restriction enzymes failed to detect major deletions or other rearrangements in the PLP gene. A human PLP cDNA was isolated and employed to similarly analyze DNA from four patients diagnosed as having Pelizaeus-Merzbacher disease. In one of these four a significant rearrangement of the PLP gene was found. These findings suggest that there may be alterations in the PLP gene in both jp mouse and Pelizaeus-Merzbacher disease.

Inherited tandem duplication dup(X) (q131-q212) in a male proband

A tandem duplication dup(X) (q131-q212) has been diagnosed neonatally because of the peculiar appearance. Family investigation demonstrated that the duplication has segregated through phenotypically normal female carriers for at least three generations. Inactivation studies showed that the aberrant X was preferentially late replicating. The difficulties related to prenatal diagnosis of minor X chromosome aberrations in males are discussed.

Multiple congenital anomalies/mental retardation (MCA/MR) syndrome due to interstitial deletion 1q

A severely retarded male infant was found to have a previously undescribed multiple congenital anomalies/mental retardation (MCA/MR) syndrome including microdolichocephaly, prominence of metopic suture, coarse scalp hair, epicanthus, anteverted nostrils, micrognathia, posteriorly angulated malformed auricles, preaxial hexadactyly, clinodactyly, camptodactyly, hypospadias, cryptorchidism, inguinal hernias, agenesis of left kidney, and pyloric stenosis. This syndrome was due to an interstitial del(1)(q25.2q31.2) associated with a paracentric inv(1)(q31.2q44).

De novo direct tandem duplication of the proximal long arm of chromosome 2: 46,XX,dir dup(2)(q11 X 2q14 X 2)

A child is described with a de novo direct duplication of the region 2q11 X 2 leads to 2q14 X 2. She probably represents the first reported case of proximal 2q duplication. The abnormalities included short stature, microcephaly, brachycephaly, depressed nasal bridge, prominent philtrum, congenital glaucoma, and mental retardation.

First trimester fetal karyotyping in twin pregnancy

Fetal chromosome analysis in a twin pregnancy during the first trimester is described. Problems of the reliability of tissue sampling are also discussed. The authors emphasise the advantage of direct cytogenetic analysis from the tissue specimens used for enzyme determination or DNA studies.

Interstitial deletion in the "critical region" of the long arm of the X chromosome in a mentally retarded boy and his normal mother

A family in which an intestitial deletion of the X chromosome, del(X)(q13q21.3), is segregating was ascertained through a boy with cleft lip and palate, agenesis of the corpus callosum, and severe mental retardation. The possible causal relationship to his chromosome abnormality is discussed. Although the deletion occurred within the critical region, the mother showed no signs of gonadal dysgenesis. A phenotypically normal daughter was, as her mother, monosomic for this region of the X, and both showed random inactivation of the X chromosome.

The origin of inverted tandem duplications, and phenotypic effects of tandem duplication of the X chromosome long arm

Tandem repeats of chromosome material can arise as inverted or as direct duplications. Such duplications of the X chromosome are instructive regarding X-linked genetic determinants of phenotype. We describe a 40-year-old woman with a direct duplication Xq13.3 to Xq27.2, short stature, gonadal dysgenesis, and secondary amenorrhea. Comparison of her phenotype with that of two other women with a direct duplication of part of Xq confirms the existence of statural determinants within the region X13 to Xq21, determinants of ovarian function within X22 to X27, and the X inactivation center within or proximal to band Xq13.3. In humans, direct duplications are more frequent than inverted, but both forms are rare. The mean age of parents is normal in subjects with direct duplications, but is advanced in subjects with inverted duplications. An inverted duplication can arise from a three-break rearrangement that includes a U-type exchange; a similar origin (two breaks and a U-type exchange) and a parental age association can be postulated for dicentric inverted duplications including dicentric isochromosome X.

Isodicentric X chromosome in a moderately tall patient with gonadal dysgenesis: lack of effect of functional centromere on inactivation pattern

An isodicentric X chromosome (46, X idic (X)(pter leads to qter::qter leads to pter)) with a single functioning centromere was found in all lymphocytes and fibroblasts examined from a female patient 171.5 cm in height presenting with primary amenorrhoea. Replication of the abnormal chromosome was consistently late. In some cells the pattern was asymmetrical but the asymmetry did not appear to relate to the position of the active centromere.

Inherited partial X chromosome duplication in a mentally retarded male

A mentally retarded male patient with a structurally abnormal X chromosome is reported (karyotype 46, dir dup (X)(p11.2 leads to p21.2)Y). In the normal mother a similar X chromosome duplication was found, which was preferentially inactivated. Xg blood groups were studied in the family. The findings indicated that recombination took place at maternal meiosis, as both karyotypically normal sons and the proband were Xg(a-), the mother being Xg(a+). Functional X chromosome disomy may explain clinical abnormalities in reported patients with X duplication and a normal Y chromosome.

A complex chromosome rearrangement resulting in trisomy 15q22 to qter

A black infant with malformations was found to have trisomy 15q22→qter. The mother had a complex chromosomal rearrangement involving three chromosomes (5, 13, and 15). A comparison with previously published cases of trisomy for distal 15q suggests a pattern of clinical findings including retardation in growth and development, microcephaly, asymmetrical facies, prominent occiput, antimongoloid slant of the palpebral fissures, micrognathia, prominent nose, and congenital heart disease.