Hair root analysis in X-linked ichthyosis.

Hair roots have been analysed in a large kindred with X-linked ichthyosis associated with steroid sulphatase deficiency. Enzyme activity in individual hair roots was assayed for the steroid sulphatase:neutral alpha-glucosidase ratio, the latter serving as an indicator of the general metabolic activity of the hair root. The distribution of the enzyme ratios in the individual hair roots in the heterozygotes described a normal curve suggesting origin from a single population of cells. The results differed strikingly from the irregular distribution of enzyme activities in hair roots of Lesch-Nyhan disease, where mosaicism occurs. It is suggested that the maternal and paternal genes for steroid sulphatase remain active in vivo in each cell in the hair root in apparent contradiction to the Lyon hypothesis. The observation is consistent with that previously reported for skin fibroblasts in vitro. Sulphatase activity in female controls was minimally greater than in males but the difference was not statistically significant.