Ceramides are
sphingolipids consisting of sphingoidbases, which are
amide-linked to
fatty acids. In the stratum corneum, they represent the major constituent of the free extractable intercellular
lipids and play a significant role in maintaining and structuring the water permeability barrier of the skin. Using thin layer chromatography, which represents the method of the first choice in analyzing the stratum corneum
ceramides, at least seven classes can be distinguished. Each
ceramide class contains various species, which have the same head group and different chain lengths. As in many other skin disorders,
atopic dermatitis and
psoriasis show derangements in content and profile of the
ceramides. Such derangements were reported for both the lesional involved as well as for the normal-appearing uninvolved skin. In this study, we focused on investigating the stratum corneum
ceramides of the uninvolved skin in
atopic dermatitis and
psoriasis patients compared to healthy skin. The aim of the investigations was to explore possible significant and specific differences which can be accomplished for purposes of early diagnostics. The skin
lipids were collected by means of an in vivo topical extraction procedure using an extraction mixture consisting of
n-hexane and
ethanol, (2:1). An automated multiple development-high performance thin layer chromatography (AMD-HPTLC) method with photodensitometric detection were applied to separate the
ceramides and to estimate their contents. For studying their molecular profile within each
ceramide class, a new method of normal phase HPLC with atmospheric pressure chemical ionization mass spectrometry were used. The results obtained by AMD-HPTLC exposed no significant alterations regarding the relative composition of the major stratum corneum
lipids and primarily the
ceramides. In addition, the mass spectrometric profiles within each
ceramide class were similar in the patients and the healthy control subjects. In conclusion, this study revealed that the normal-appearing uninvolved skin of
atopic dermatitis and
psoriasis patients does not prove significant or specific deficiencies with respect to the free extractable major stratum corneum
lipids and mainly the
ceramides, when compared to healthy skin. Thus, they cannot be used for diagnostic purposes. Furthermore, our data are not consistent with the concept that impairments in the
ceramide composition represent an obligate etiologic factor for both diseases.