On the basis of clinical, histological, and cellular kinetic observations, a separation of the major ichthyosiform dermatoses into four groups is proposed.
Ichthyosis vulgaris patients have dry skin and fine scales on their trunk and extremities, but gross changes in the skin of their legs may be more severe. A granular layer is histologically absent.
Lamellar ichthyosis patients have large, coarse scales. The granular layer is prominent in this condition.
Epidermolytic hyperkeratosis consists of a clinical spectrum of disorders; generalized forms may be bullous, and localized forms may resemble linear nevi. Intracellular and intercellular edema gives the epidermis a characteristic reticular pattern in histological sections.
Psoriasiform erythroderma is clinically and histologically indistinguishable from universal psoriasis.
Increased mitotic activity and consequent increased scale formation appear to be important pathogenetic features in these disorders, except for ichthyosis vulgaris in which mitotic counts were actually lower than in the control specimens.