This generalized scaling eruption of the skin is either idiopathic or secondary to underlying cutaneous or systemic disease. Appreciation for this condition requires an understanding of the skin's normal epithelial layer.
Normal epidermis has a continual turnover of epithelial cells.
Cell division occurs near the basal layer. As cells move toward the periphery, they become well keratinized. This process requires about 10-12 days. Cells subsequently remain in the stratum corneum for another 12-14 days prior to being sloughed off. The mechanism responsible for this is not known, though an immunologic basis has been suggested.