ABSTRACT
The heterogeneous group of disorders collectively known as (Latin for fishlike) features widespread hyperkeratosis with or without epidermal hyperproliferation. Whereas the common normoproliferative form (ichthyosis vulgaris) shows no significant abnormalities in the epidermal vitamin A content (196), the rarer hyperproliferative forms (lamellar ichthyosis and congenital ichthyosiform erythroderma) are usually associated with low retinol and slightly elevated 3-dehydroretinol levels The retinol/3-dehydroretinol ratio observed in hyperproliferative is in fact 10 times lower than in normoproliferative skin. There are no abnormalities in the plasma retinol and RBP concentrations in patients with ichthyosis (196,198), suggesting the possibility of a defective epidermal vitamin A metabolism. The decreased immunostaining for RBP in upper epidermis seen in ichthyosis vulgaris is probably secondary to the absence of a
layer (199).
