Quantitative analysis of stratum corneum lipids in xerosis and asteatotic eczema.

Sphingolipids, a major constituent of intercellular lipids, are an important determinant for both water-holding and permeability barrier function in the stratum corneum. To assess the pathogenic role of sphingolipids in the stratum corneum of dry skin disorders such as xerosis and asteatotic eczema in leg skin, ceramides were quantified by thin layer chromatography after n-hexane/ethanol extraction of resin-stripped stratum corneum and evaluated as micrograms/mg stratum corneum. In healthy leg skin (n = 49), there was age-related decline in the total ceramide, whereas xerosis (n = 25) and asteatotic eczema (n = 16) suffering significantly reduced water-holding properties, exhibited no definite decrease, rather slight increase in ceramide quantity with the same composition of each individual ceramide as compared to healthy age-matched controls. These data indicate that the seemingly elevated level of ceramide is an artificial effect due to inflammatory processes which result from susceptibility to dryness. Analysis of sebum-derived lipids present in the stratum corneum revealed that there was a significant decline in free fatty acids in xerosis and asteatotic eczema as compared to age-matched healthy controls, and a similar decline in triglycerides in the above three groups when compared to younger controls. Although the observed decrease in the stratum corneum lipids may well explain the high incidence of winter dry skin in older people, the progression toward asteatotic eczema can not be accompanied solely by a decrease in ceramide quantity, suggesting that the evolution of xerotic skin is associated with other moisturizing factors and/or environmental stimuli.