Background: X-linked ichthyosis (XLI) is caused by deficiency of steroid sulfatase (STS) activity. About 90% XLI patients have large deletions involving the entire STS gene and flanking regions. Recently, VCXA, which is located approximately 0.7Mb telomeric to the STS gene, was reported as a candidate gene for mental retardation (MR) in patients with XLI.
Objective: To delineate the X-chromosomal deletion of a XLI patient with borderline mental retardation.
Methods: We carried out FISH analysis to show that the whole STS gene is deleted, and PCR analysis for fine-scale deletion mapping.
Results: The deleted segment is approximately 1.6Mb in size, and includes the entire STS and VCXB1 genes. VCXA itself is intact, but its promoter is deleted.
Conclusion: A deletion that includes the VCXA promoter is associated with borderline mental retardation in a patient with XLI.