Objective measurement of three epidermal parameters in psoriasis vulgaris and in dermatopathology in general.

Three objective parameters which characterize the main features of the epidermis are described. One parameter relates to the mean thickness of the epidermis determined by a simple method. The second descriptive number is the ratio of the thickness of the strata corneum, lucidum and granulosum to the stratum malpighii. The third number relates to the degree of folding of the dermo-epidermal junction. The ratio of the mean thickness of abnormal to normal stratum corneum (for the same skin region) is suggested as an objective measure of hyperkeratosis; likewise, the ratio of abnormal to normal stratum malpighii is an objective measure of acanthosis. A single parameter can be measured against time to follow changes during the pathogenesis, treatment or remission of epidermal disease. As psoriasis undergoes progressive acanthosis, the geometry of the folding of the dermo-epidermal junction is such that cells of the stratum malpighii retain their close association with the cylindrical dermal papillae.