Assays / Genetic Enzymes / X-Linked Ichthyosis

X-linked ichthyosis is one of the more frequent X-linked conditions. Ichthyosis, which is a disorder in which there is visible scales of the skin likened to adherent fish scales, is present at birth in about one-fifth of affected male patients, and becomes evident in the others at the end of the first year. Females are not affected, and the incidence is about 1 in 6000 males. The disease is due to deficient activity of the enzyme steroid sulphatase, which can be demonstrated in cultured fibroblasts using tritiated dehydroepiandrosterone sulphate as substrate. This enzyme appears to be identical to arylsulphatase C and an alternative assay uses an artificial substrate to measure this activity. In the SAS laboratory both methods are employed.

ENZYME TESTS: The disease is due to deficiency of steroid sulphatase (arylsulphatase C).

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