Yiu Maria, Qi Zhongxia, Ki Anita, Yu Jingwei
Department of Laboratory Medicine, University of California, San Francisco. 185 Berry Street, Suite# 290, Campus Box 0134, San Francisco, CA 94107 USA.
Clinical Cytogenetics Laboratory, UCSF Medical Center, San Francisco, CA USA.
Mol Cytogenet. 2015 Jul 25;8:53. doi: 10.1186/s13039-015-0160-5. eCollection 2015.
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.
绒毛取样的细胞遗传学分析显示为嵌合核型，伴有一条重排的X染色体增加。微阵列及其他研究表明，重排的X染色体携带一个倒位重复、一个缺失和一个带有随体的Xqter。后续的羊膜穿刺术和产后脐带血样本证实了这条重排X染色体的增加。一名足月女婴出生，出生时及21个月随访检查时体格检查均正常。延迟复制研究表明，重排的X染色体在所有分析的异常细胞中均失活。X染色体失活偏倚可能会抑制基因组失衡的潜在有害影响；然而，X染色体增加，尤其是重排的X染色体，常常给产前遗传咨询带来挑战。临床表型严重程度的分级通常与额外X染色体的数量相关。然而，导致异常表型的X染色体区域尚不清楚。该病例将进一步阐明X染色体失活和X染色体异常的表型效应。
