The quantification of free sphingosine in the stratum corneum of patients with hereditary ichthyosis.

Sphingosine is a long-chain base which provides the back-bone of all sphingolipid molecules. Free sphingosine is found in normal epidermis, especially in the stratum corneum. As a free molecule it may modify epidermal cell proliferation and differentiation through its inhibition of protein kinase C. Using a thin-layer chromatography technique we have demonstrated in vitro that the erythrodermic ichthyoses show significantly lower levels of stratum corneum sphingosine than the non-erythrodermic types. The exact in vivo significance of this finding is unclear, but free sphingosine may have an important role in determining the inflammatory component of the hereditary ichthyoses.