Detection of chromosomal abnormalities in the dysmorphic fetus using fluorescence in situ hybridization: evaluation for monosomy X genotype.

The cytogenetic abnormalities of dysmorphic fetuses who died in utero cannot be analyzed reliably by karyotyping. To overcome this obstacle, the authors applied fluorescence in situ hybridization (FISH) to formalin-fixed, paraffin-embedded tissue of two female infants and 13 female fetuses whose phenotypic features suggested possible Turner's syndrome. Previous cytogenetic evaluation of the amnionic fluid showed five were 45,XO karyotype; two were 46,XX karotype; and eight were of unknown karyotype. Karyotyping had been attempted on four of the unknown cases without success. The copy number of X chromosomes were correctly identified by FISH in all previously karyotyped cases. Of the remaining eight cases with unknown karyotype, three appeared to be XX, and five cases were identified as monosomy XO, confirming the suspicion of Turner's syndrome genotype. FISH is useful for confirming suspected Turner's syndrome genotypes in infants and macerated fetuses in which a karyotype cannot be obtained otherwise.