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

Delineation of an inverted tandem Xq23-26.3 duplication in a female featuring extremely short stature and mild mental deficiency

BACKGROUND

Partial duplications involving the long arm of the X chromosome are associated with mental retardation, short stature, microcephaly, and a wide range of physical findings. Female carriers usually have no clinical phenotype. Occasionally, they may also have heterogeneous features due to non-random inactivation of the X chromosome.

METHODS

The peripheral blood sample was collected from the patient and subjected to a few genetic testing, including chromosomal karyotyping, Chromosomal microarray analysis (CMA), Optical genome mapping, short tandem repeat (STR) analysis for Determination of parental origin, and X chromosome inactivation (XCI) analysis.

RESULTS

We have identified a de novo Xq23-Xq26.3 duplication in an adult female featuring extremely short stature and mild mental deficiency. Chromosome analysis detected a duplication on Xq23-q26.3 with a size of approximately 20 Mb. The duplication region has encompassed a number of genes, among which ARHGEF6, PHF6, HPRT1 and SLC9A6 are associated with X-linked mental retardation. Further analysis suggested that the duplication has derived from her father, was of the inversion duplication type and involved various degrees of skewed X chromosome inactivation.

CONCLUSION

Correlation with her phenotypes might indicate new mechanisms by which the X chromosome may lead to short stature and mental retardation. Our findings thereby may shed more light on the phenotypic implication of functional disomy of X-chromosome genes.

Association between clinical variations and copy number variations in cases with Turner syndrome

OBJECTIVES

Turner syndrome (TS) is one of the most common chromosomal abnormalities with an incidence of approximately one in 2,500 live births. Short stature and primary ovarian insufficiency are two most important characteristic findings of TS. Turner syndrome karyotypes include monosomy X, mosaic structure and X chromosome structural anomalies. Genotypic and phenotypic characteristics vary among cases. This study aimed to evaluate the clinical variations observed in TS cases with the copy number variations (CNV) detected by microarray study.

METHODS

Fifty-three patients diagnosed with TS, between the ages of 0-18 were included in the study. Peripheral blood samples were taken from 36 cases for microarray study.

RESULTS

Karyotypes were as follows: thirty-three of cases were 45,X, 7 were 45,X/46,XX, 6 were 45,X/46,Xi(Xq), 2 were 46,Xi(Xq), 2 were 45,X/46,r(X), 1 was 45,X/46,Xi(Xp), 1 was 45,X/46,XY and 1 was 45,X/46,X+mar(idicY) karyotype. A significant correlation was found between karyotype groups and FSH values of the cases (p=0.034). In monosomy X and mosaic isochromosome Xq cases, the FSH value was found to be significantly higher than those with 45,X/46,XX mosaic karyotype. CNVs were found in 8 (22.2%) out of 36 cases whose microarray study was performed. Unexpected atypical findings were discussed in the light of the characteristics of CNVs.

CONCLUSIONS

In conclusion, the microarray method has a great contribution in explaining many unexpected findings in TS cases. Moreover, those CNV findings may contribute for the explanation of the underlying mechanisms of those anomalies.

Mosaic Xq duplication, or 46,X,der(X)dup(X)(q22.1q22.2)dup(X)(q25q22.3)/ 46,XX at amniocentesis in a pregnancy with a favorable outcome

OBJECTIVE

We present mosaic Xq duplication, or 46,X,der(X)dup(X)(q22.1q22.2)dup(X)(q25q22.3)/46,XX at amniocentesis in a pregnancy with a favorable outcome.

CASE REPORT

A 40-year-old woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a result of 46,X,der(X)dup(X)(q22.1q22.2)dup(X)(q25q22.3)[7]/46,XX[20]. Simultaneous array comparative genomic hybridization (aCGH) analysis on the DNA extracted from uncultured amniocytes revealed the result of arr (1-22, X) × 2. Cytogenetic analysis on maternal blood revealed a karyotype of 46,XX. At 22 weeks of gestation, she underwent repeat amniocentesis which revealed a karyotype of 46,XX in 22/22 colonies of cultured amniocytes and an aCGH result of (1-22, X) × 2 in the uncultured amniocytes. Prenatal ultrasound findings were unremarkable. The parents decided to continue the pregnancy, and a healthy female baby was delivered at 39 weeks of gestation with a body weight of 3510 g and a body length of 49 cm. The cord blood had a karyotype of 46,X,der(X)dup(X)(q22.1q22.2)dup(X)(q25q22.3)[3]/46,XX[37]. At age two months, interphase fluorescence in situ hybridization (FISH) analysis on buccal mucosal cells showed Xq duplication signals in 1.25% (1/80 cells), compared with 0% (0/90 cells) in the normal control. At age nine months, the neonate had normal physical and psychomotor development. Her body weight was 9.6 Kg (85th - 97th centile), and body length was 72 cm (50th - 85th centile). Cytogenetic analysis of peripheral blood revealed a karyotype of 46,X,der(X)dup(X) (q22.1q22.2)dup(X)(q25q22.3)[1]/46,XX[39]. Interphase FISH analysis on 100 buccal mucosal cells revealed no abnormal signal.

CONCLUSION

In case of mosaicism for an Xq duplication with a normal euploid cell line at amniocentesis, the in-vitro culture process of amniocytes may cause over-estimation of the mosaic level for the aberrant chromosome because of culture artifacts, and the abnormal cell line can decline after birth.