Most "sporadic" cases of X-linked ichthyosis are not de novo mutations

X-linked ichthyosis is an inherited disease with dark, regular and adherent scales as clinical characteristics. It is caused by a deficiency of the st eroid sulphatase enzyme. Steroid sulphatase assay is a relative easy tool t hat enables correct diagnosis of X-linked ichthyosis patients and carriers, A large number of X-linked ichthyosis patients correspond to non-familial cases that seem to represent de novo mutations. In this study, we examined the X-linked ichthyosis carrier state of the mothers of 42 non-familial cas es to determine whether their children corresponded to de novo mutations. T o classify patients and carriers, a steroid sulphatase assay was performed in leukocytes using 7-[H-3]-dehydroepiandrosterone sulphate as substrate. I n 36 mothers (85%) we found steroid sulphatase activity compatible with the carrier state of X-linked ichthyosis. This data suggest that most of the m others of these patients present the primary gene defect, excluding de novo mutations in the patients.