A rare case of de novo structural rearrangement of X chromosome diagnosed by amniocentesis

De novo isodicentric X chromosome: 46,X,idic(X)(q24), and summary of literature

We describe a 12-year-old patient, the second live born prenatally ascertained patient in the literature, with a de novo isodicentric X chromosome, karyotype 46,X,idic(X)(q24), with normal growth and development and lack of dysmorphic features. Molecular and cytogenetic studies were performed to further characterize the isodicentric chromosome X behavior. Literature on isodicentric X chromosomes with various breakpoints on Xq is reviewed and summarized.

Pregnancy outcome following prenatal diagnosis of an isodicentric X chromosome: first case report

An isodicentric X chromosome, idic (X)(q27) was found in a female fetus during cytogenetic studies performed on amniotic cells due to advanced maternal age. No mosaicism was observed. Although segmental inversion duplications have been described for several other chromosomes, isodicentric chromosomes are reported only for gonosomes. Genetic counselling was based on ultrasound findings, cytogenetic replication studies and published cases of X chromosomes duplications ascertained pre- and postnatally. The pregnancy resulted in the birth of a healthy female infant.

An unusual tricentric X chromosome detected prenatally

We describe a female fetus with a de novo X chromosome rearrangement detected prenatally in both chorion villi and a pleural effusion. Chromosome painting showed the chromosome to be composed entirely of X chromosome material, while G-banding indicated a duplication of X short arms, four copies of the proximal long arm, and deletion of the distal long arm of the X. C-banding showed the presence of one active and two inactive centromeres and X-inactivation studies demonstrated the tricentric chromosome to be late replicating in all cells examined. The origin of this complex de novo rearrangement appears to have involved two separate breakage events, the first leading to the production of a dicentric X chromosome and the second generating the tricentric X.