keratosis

a condition of the SKIN whereby there is a thickening and overgrowth of the horny layer (or stratum corneum) of the skin. The condition is usually induced by excessive sunlight and can occur as scales and patchy skin pigmentation (actinic keratosin) or as yellow/brown warts (seborrhoeic keratosis). It is essential to avoid overexposing the skin to sunlight if it is to be prevented or treated.