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

A case of recessive X-linked ichthyosis: scale-specific abnormalities of lipid composition may explain the pathogenesis of the skin manifestation

We analyzed the lipid content of the scales, red blood cells, and plasma from a recessive X-linked icthyosis patient. The patient's scales accumulated cholesterol sulfate, had decreased levels of free sterols, sterol esters and sphingolipids, and lacked phospholipids. Although the accumulation of cholesterol sulfate was found in the patient's red blood cells and plasma as well as in the scales, other lipid composition abnormalities were specific for scales. Such scale-specific abnormal lipid composition may explain the pathogenesis of generalized hyperkeratosis and abnormal scaling of the disease.

Quantification of stratum corneum ceramides and lipid envelope ceramides in the hereditary ichthyoses

Ceramides (sphingolipids) are the main polar lipids of the stratum corneum and play an important role in skin barrier function, cell adhesion and epidermal differentiation. In view of the function of ceramides in normal skin, this study aimed to assess their levels in patients with various types of hereditary ichthyosis, in which epidermal homeostasis is markedly abnormal. Stratum corneum samples were collected from 80 patients and 23 normal controls, and the intercellular and lipid envelope ceramides were analysed by high-performance thin-layer chromatography. The covalently bound ceramides (ceramides A and B) of the lipid envelope were present in all patients studied, and showed no significant differences from control samples. Total ceramides (ceramides 1-6) were decreased in bullous ichthyosiform erythroderma, which is presumably a secondary phenomenon similar to that seen in patients with atopic dermatitis. Patients with non-erythrodermic lamellar ichthyosis showed a marked decrease in levels of the important acylceramide, ceramide 1, whereas those with other types of autosomal recessive ichthyosis (limited lamellar ichthyosis and non-bullous ichthyosiform erythroderma) had mean levels similar to the controls. Ceramide 1 deficiency may therefore define a subgroup within the autosomal recessive ichthyoses. Sjögren-Larsson syndrome (SLS) shows a deficiency of both acyl-ceramides (ceramides 1 and 6), which would seem likely to disrupt the normal skin barrier function. Furthermore, glucosylceramides (cerebrosides) are known to be deficient in the neural tissue of patients with SLS. The relationship of these ceramide abnormalities to the underlying fatty alcohol oxidoreductase defect remains uncertain, but they may provide an interesting link between the nerve damage and cutaneous abnormalities seen in this rare neurodermatosis.