X-linked ichthyosis in Mexico: high frequency of deletions in the steroid sulfatase encoding gene.

The present study analyzes the frequency of molecular deletions in the steroid sulfatase (STS) encoding gene in a sample of 50 Mexican subjects with biochemical diagnosis of X-linked ichthyosis (XLI). To establish the correct diagnosis, STS activity was determined in leukocytes using 7-(3)H-dehydroepiandrosterone sulfate as the substrate. No amplification of the 3' and 5' ends of the STS gene by PCR was detected in the DNA of 49 patients, whereas only one sample of 50 presented a normal amplification. This report shows a very high frequency of deletions in the human STS encoding gene in a representative sample of the Mexican population, and it defines the characteristics of XLI in patients whose STS gene has a complete deletion as a major molecular defect.