Isodicentric X chromosome in a girl with gonadal dysgenesis.

Chromosomal analysis on a 15-year-old girl with amenorrhea and lack of secondary sexual development showed a normal X chromosome and an isodicentric X chromosome, 46,X, idic(x) (pter leads to q23::q23 leads to pter). Thus the patient has duplicated and deleted X chromosome material. There was no evidence of 45,X mosaicism. Brd U-labeling revealed the abnormal X to be late-replicating.