Interphase fluorescence in situ hybridization in a Turner syndrome variant with IsoXq. A case report.

BACKGROUND

Performing fluorescence in situ hybridization (FISH) on uncultured amniotic fluid cells has been known to produce rapid diagnoses of major chromosomal aberrations. However, if the aberration involves a structural chromosomal anomaly, the FISH result may be not only uninformative but misleading.

CASE

FISH with alpha-satellite probes of chromosomes X and Y was performed on the uncultured amniocytes of a prenatal amniotic fluid specimen. Eighty-five percent of the hybridized interphase nuclei displayed two signals when probing with X; no significant hybridization was found when probing with Y. This FISH result was interpreted as normal, disomic for chromosome X. Cytogenetic analysis later, however, disclosed the fetal karyotype to be 46,X,i(Xq).

CONCLUSION

Interphase FISH with an alpha-satellite probe (or probe made of repeat centromeric sequences) may be useful in the detection of a numerical anomaly of a chromosome but not of a structural anomaly within the chromosome itself.