Carrier identification in steroid sulphatase deficiency and recessive X-linked ichthyosis

Steroid sulphatase (STS) activity was measured with tritiated dehydroepiandrosterone sulphate (DHEAS) and oestrone sulphate (OES) in leucocytes as well as in skin fibroblasts from 31 women who were presumed to be carriers of STS deficiency and recessive X-linked ichthyosis. Overall, 30 of the 31 women (96.8%) could be identified as heterozygotes in at least one of the four assay systems used, i.e. on the basis of having an STS activity below the 2.5 percentile calculated for normal control females. In the individual assay systems, the highest carrier detection rate was achieved with OES in leucocytes (96.2%), followed by DHEAS in leucocytes (80.8%), whereas a more pronounced overlap was present in the fibroblast systems. In leucocytes as well as in fibroblasts, the STS activity determined with DHEAS was positively correlated with the STS activity determined with OES (p less than 0.001) suggesting that a single sulphatase is responsible for the hydrolysis of both steroid sulphates.