Deletions of the steroid sulphatase gene in "classical" X-linked ichthyosis and in X-linked ichthyosis associated with Kallmann syndrome.

We have studied 16 men, from 10 unrelated Italian families, affected by steroid suphatase (STS) deficiency, which is the basic defect of X-linked ichthyosis (XLI). The patients' clinical diagnoses were of either isolated ichthyosis or ichthyosis associated with Kallmann syndrome (KS) (hypogonadotropic hypogonadism and anosmia). DNA from patients and their relatives was analysed by Southern blotting followed by hydridization with an STS cDNA probe. None of the patients affected by either XLI or XLI/KS showed any hybridization signal, thus revealing a deletion in the STS gene. We suggest that a gene deletion may be the most common molecular defect involved in XLI and that the syndrome XLI/KS may be due to a deletion of both the STS and the KS loci.