Identification of sex chromosomal abnormalities by fluorescence in situ hybridization

Chromosomes can be specifically stained in metaphase spreads and interphase nuclei by fluorescence in situ hybridization (FISH). Case 1 was a 20 year-old female patient who had chromosomal analysis six years ago because of primary amenorrhea and short stature. Three cell lines were identified: 45, X (20%); 46, X plus an unidentifiable fragment (50%) and 46, X plus an isodicentric X chromosome of short arm fusion (30%). Case 2 was a 6 year-old girl with the problems of clitoromegaly and growth retardation. By use of in situ hybridization with biotinylated X and Y centromere-specific alpha repetitive sequence probes, we were able to identify the marker chromosomes to be X and Y-chromosome originated, respectively. The use of FISH can facilitate clinical cytogenetic diagnosis, and allows fast screening of a large number of metaphases. This technique is applicable to the screening of other types of chromosomal mosaicism as well.