Steroid sulfatase activity in nails: screening for X-linked ichthyosis.

X-linked ichthyosis is generally diagnosed by a deficiency of steroid sulfatase activity in fibroblasts or leukocytes. We established a method of assaying nail steroid sulfatase activity for diagnostic use. Nail samples were easy to collect and handle, and satisfied the screening criteria of accuracy, sensitivity, and stability. The detergents Tween 20 and Triton-X 100, which enhance nail STS activity, enabled us to assay the activity with small amounts of nails. The detergent-facilitated assay was also suitable for use with pediatric patients, from whom small amounts of nails were collected.