X chromosome deletions detectable by flow cytometry in some patients with steroid sulphatase deficiency (X-linked ichthyosis).

The X chromosomes of individuals with isolated steroid sulphatase deficiency (X-linked ichthyosis) from ten families were studied by flow karyotype analysis. In four of the families, a small but significant reduction in the relative fluorescence of the X chromosome was detected consistent with a deletion ranging from 1.2%-3.4% of the X and amounting to a DNA loss of 1.9-5.2 million base pairs. In the remaining six families, three of which demonstrated a molecular deletion of the DNA sequence GMGX9 (DXS237), the relative fluorescence of the X chromosomes was indistinguishable from normal. The phenotypes of those with X deletions detectable by flow cytometry were similar to those of patients without such deletions.