Involucrin represents a soluble precursor of the cross-linked envelope of the horny layer and may, thus, be considered as a marker of normal keratinocyte differentiation and maturation The expression of involucrin has so far been studied mostly
in
psoriasis and cutaneous tumors. However, in keratiniaing disorders, involucrin has yet been sparsely studied.
The purpose of this study is to document characteristic involucrin expression using immunoperoxidase technique in a total of 6 specimens of normal human skin and 44 specimens from a variety of keratinizing disorders including palmoplantar
pustular
psoriasis, pityriasis rubra pilaris, and disseminated superficial actinic porokeratosis.
In normal human epidermis one third of the living epidermis was labelled, intracellularly.
The diseases studied fell into two groups : diseases with greatly increased staining and diseases with normal or slightly increased staining. Two main patterns of reactivity were observed : diffuse intracellular staining and staining at cell
borders.
Greatly increased, cell border staining was shown in psoriasis vulgaris and palmoplantar pustular psoriasis. Greatly increased, intracellular staining was shown in pityriasis rubra pilaris. And normal or slightly increased, intraceilular staining
was
shown in ichthyosis vulgaris, disseminated superficial actinic porokeratosis and epidermal nevi. The diseases which showed increased involucrin expression might show precocious expression because of their rapid epidermal proliferation and
turnover.
These results demonstrate that involucrin expression is altered in some keratinization disorders, and they may aid in the understanding of keratinocyte differentiation and histogenesis of those disorders.
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