Abstract
Activity of the microsomal enzyme, steroid sulfatase, is absent in keratinocytes, fibroblasts, and leukocytes of patients with recessive x-linked ichthyosis. This study was undertaken to determine if cholesterol sulfate, a substrate of this enzyme, accumulates in the pathological scale of these patients. Scales from 8 patients with recessive x-linked ichthyosis, 10 patients with other forms of ichthyosis, and normal human outer stratum corneum were extracted with chloroform/water (1:2:0.8 by vol) and lipids were fractionated by quantitative, sequential thin-layer chromatography. Cholesterol sulfate was identified by cochromatography in several solvent systems, by its staining characteristics, by biochemical analysis, and by mass spectrometry. The mean cholesterol sulfate content of recessive x-linked ichthyotic scale was 12.5 +/- 0.8% of the total lipid, a fivefold increase over normal (P less than 0.0025), whereas the cholesterol sulfate content of other ichthyotic scale was normal. This increase in cholesterol sulfate content was accompanied by a decrease in total neutral lipids (P less than 0.0025) and free sterols (P less than 0.025) but no change in sterol esters or total sterols. These results demonstrate that deficiency of steroid sulfatase in recessive x-linked ichthyosis results in excessive accumulation of a substrate, cholesterol sulfate, in the pathologic scale, which may underly the pathogenesis of the scaling in this disorder. Measurement of cholesterol sulfate content in scale provides an alternative method to enzymatic assay for the diagnosis of this form of ichthyosis.
Authors
M L Williams, P M Elias
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