The process of epidermal cell renewal, differentiation, and shedding is an exquisitely well-balanced, smoothly functioning system in normal persons. Modern interest in the epidermis has focused primarily on rates and control of cell renewal and on the composition of keratin and keratohyalin polypeptides. Until recently, except for pharmacologic studies of percutaneous penetration, comparatively little consideration has been directed toward the stratum corneum as an organized tissue with cohesive forces that initially hold together its cells and later permit their orderly shedding as small, clinically inapparent bits of material. Yet excessive accumulation and retention of stratum corneum are clinically of great importance in patients with both generalized scaling dermatoses (eg, psoriasis and ichthyosis) and localized hyperplasias (eg, warts and calluses).
RECESSIVE X-LINKED ICHTHYOSIS (RXLI) AND STEROID SULFATASE
Although many pharmacologic agents are available for the treatment of hyperkeratosis, usually these are only modestly effective, and little is known about their mechanism