A duplication within the critical fertility region of X chromosome in a mentally retarded woman with normal menarche

Duplication of Xq26.2-q27.1, including SOX3, in a mother and daughter with short stature and dyslalia

Duplications of the distal long arm of the X chromosome are rare and carrier females are usually phenotypically normal. We report on a 14-year-old short statured (height and weight <3rd centile) girl with dup(X)(q26.2q27.1) inherited from a short mother. The proband has minor dysmorphic features, lordosis, lack of menarche, late signs of puberty, low prepuberal levels of gonadotrophins and steroids, but borderline low IGF-1 and normal IGF-Bp3 serum levels. Both the proposita and her mother have severe speech problems with stuttering and dyslalia. The 44-year-old mother with a strikingly aged face and a prominent nose, had menarche at 15 years. Both maternal sisters and the grandmother of the proposita are also short. Karyotyping revealed an additional band at Xq26 in all metaphases from the proband, her mother, and two maternal aunts. Molecular cytogenetic investigations revealed an Xq26.2-q27.1 direct duplication of approximately 7.5 Mb that encompasses or disrupts the SOX3 gene, which maps at the distal border of the duplicated segment. A similar chromosomal duplication was reported recently in five families and in each was associated with an abnormal phenotype in males with short stature [Hol et al., 2000; Solomon et al., 2002, 2004]. Using an androgen-receptor (HUMARA) gene methylation assay and FISH, we show that despite preferential inactivation of the dup(Xq) chromosome a significant proportion of lymphocytes in both mother and daughter carry an active duplicated X chromosome. Our findings further suggest that a dosage effect of SOX3 may to be responsible for a speech disorder in addition to short stature secondary to hypopituitarism.

De novo interstitial direct duplication of Xq21.1q25 associated with skewed X-inactivation pattern

Genotype-phenotype correlation in women with an abnormal phenotype associated with a duplication of the long arm of the X chromosome remains unclear. We report on prenatal diagnosis and follow-up of a girl with an Xq duplication and dysmorphic features. The abnormal phenotype included growth retardation, hypotonia, and nystagmus. In order to improve the resolution of the cytogenetic analysis, we used both conventional and array-based comparative genomic hybridization to perform a global molecular cytogenetic analysis of the genome. These molecular cytogenetic analyses showed a direct duplication Xq21.1 --> q25 without other chromosomal abnormalities. This duplication was originating from the paternal X chromosome. Moreover, a skewed X-inactivation pattern was observed leading to a partial functional disomy of the chromosomal region Xq21.1q25. This report and review of the literature suggest that functional disomy for chromosome X could explain the abnormal phenotype. In prenatal diagnosis, this can have implication for patient management and genetic counseling.

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.

Prader-Willi-like syndrome in a patient with an Xq23q25 duplication

We report on a 24-year old woman with an Xq duplication and findings suggestive of Prader-Willi syndrome (PWS). Her birth weight was at the 3rd centile and her birth length was less than the 3rd centile. She was hypotonic and had a weak cry as an infant. There were no feeding difficulties, although her mother reports that as an infant, she was "small for her age." Excessive weight gain began between 3 and 4 years. The patient's development was delayed and she received special education. She has a history of hiding food. She has a sleep disturbance disorder and inappropriate social behavior. At the age of 24 years her height was below the 5th centile and weight >>95th centile. She has physical findings typical of PWS, skin picking, and speech articulation defects. Cytogenetic analysis showed a 46,X,dup(X)(q23q25) karyotype. Fluorescent in situ hybridization (FISH) studies using a chromosome X painting probe demonstrated that the rearrangement was intrachromosomal. The X-chromosome fold scoring technique was used to determine the X inactivation pattern and indicated that some cells expressed the abnormal X chromosome. Results of FISH studies using the SNRPN probe localized to 15q11q13 and DNA studies using the PW71B and SNRPN probes were normal. The duplicated X chromosome, random X inactivation pattern, and the negative molecular studies for PWS indicate that the abnormal X chromosome is the basis of this patient's phenotype. This patient emphasizes the importance of obtaining a karyotype even when a syndrome diagnosable by molecular methods is strongly suspected.

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.

"De novo" duplication Xq23-->Xq26 of paternal origin in a girl with a mildly affected phenotype

We report a de novo dup(X)(q23-->q26) in a 3-year-old girl with growth retardation, developmental delay, and minor anomalies. X-inactivation in lymphocytes by BRDU labeling showed the abnormal X was late replicating. The androgen receptor assay (HAR) demonstrated a skewed methylation (88.8%) of the paternal allele and a 11.2% methylation of the maternal allele. These data, which suggest the duplication was paternally inherited, are the first parental-origin identification of a duplication Xq. The mild phenotype of the patient may be related to the size and region of the duplication, the low percentage of a dup(X) active detected by the HAR assay, or a combination of these mechanisms.

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.

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.