queratosis

Keratosis, sometimes spelled queratosis in some languages, is a dermatological term referring to thickening of the stratum corneum, the outermost layer of the skin, due to excess keratin production or slowed shedding. Keratoses can be benign or premalignant and commonly appear as rough, scaly patches or warty growths on the skin.

Common forms include actinic keratosis, which occurs on sun-exposed skin as rough, scaly patches and is considered precancerous; it may progress to squamous cell carcinoma, especially with aging or immune suppression. Seborrheic keratosis consists of benign, pigmented, stuck-on plaques that are usually harmless and may be removed for cosmetic reasons. Keratosis pilaris presents as small, rough bumps around the upper arms or thighs due to keratin plugging of hair follicles and is typically asymptomatic. Hyperkeratosis is a general term for thickened skin that can occur in various conditions, often related to chronic irritation or friction.

Causes and risk factors include sun exposure, aging, genetic predisposition, friction from clothing or footwear, inflammatory skin diseases, and sometimes infection with human papillomavirus in the case of certain warts. Diagnosis is usually clinical, based on appearance; biopsy or dermoscopy may be used if cancer is suspected or the diagnosis is uncertain.

Management depends on the type and symptoms. Benign keratoses may require no treatment. Options for actinic keratosis and other troublesome lesions include topical keratolytics (such as salicylic acid or urea), cryotherapy, curettage, or prescription therapies like topical 5-fluorouracil, imiquimod, or diclofenac gel, and, in some cases, photodynamic therapy. Regular monitoring is advised for lesions with cancer risk or any changes in size, color, or shape.