PRENATAL-DIAGNOSIS OF X-LINKED ICHTHYOSIS USING MOLECULAR CYTOGENETICS

A case is presented in which X-linked ichthyosis was diagnosed prenata lly using fluorescence in situ hybridization. Fetal sex was known by s econd trimester ultrasound in a woman with very low second trimester M SUE3. All of the 15 maternal peripheral blood metaphase spreads examin ed displayed two hybridization signals on one X chromosome (one in the steroid sulfatase region (Xp22.3) and one in the centromeric region), but only one hybridization signal (in the X centromeric region) on th e other X chromosome. Thus, one of the X chromosome had a deletion in the Xp22.3 region, a result which was consistent with carrier status f or steroid sulfatase deficiency and X-linked ichthyosis. In the 15 met aphase spreads that were examined from the amniotic fluid sample, the X chromosome displayed one hybridization signal in the control region, but no hybridization signal in the steroid sulfatase region. Thus, th e X chromosome of this male fetus had a deletion in the steroid sulfat ase region, a result that was consistent and demonstrated postpartum X -linked ichthyosis.