Detection of heterozygotes of X-linked ichthyosis by measuring steroid sulphatase activity of lymphocytes. Mode of inheritance in three families.

Steroid sulphatase activity in peripheral blood lymphocytes was assayed in all available members of three families in which cases of X-linked ichthyosis were frequently seen. Lymphocytes from all the patients with this disease lacked steroid sulphatase activity and some female members who were probably heterozygotes, showed significantly lower enzyme activity compared with other healthy family members and normal controls. This suggest that females heterozygous for X-linked ichthyosis in these families could be traced enzymatically. Three childless females in these families were found to be possible heterozygotes in view of their lower enzyme levels. It was found that polyacrylamide gel electrophoretic mobility of serum low-density lipoproteins was increased in X-linked ichthyosis patients but was not changed in the probable heterozygotes. The detection of individuals heterozygous for X-linked ichthyosis, for the purpose of precise genetic counselling, may be possible by measuring steroid sulphatase activity of peripheral blood lymphocytes.