Actinic keratosis most commonly occurs on which areas of the body?

• A. Sun-exposed areas of the skin such as the face, ears, and dorsal hands
• B. Non-exposed areas such as the buttocks
• C. Palms and soles
• D. Mucous membranes

Answer: (A)

Actinic keratosis arises from cumulative damage to epidermal keratinocytes caused by ultraviolet light. This damage tends to appear on skin that is frequently exposed to the sun, especially in areas with long-term UV exposure like the face, ears, and the dorsal surfaces of the hands. Areas not regularly exposed to sunlight, such as the buttocks, or skin that is thick and less UV-accessible like the palms and soles, are much less likely to develop these lesions. Mucous membranes are also not typically exposed to UV light, so actinic keratoses are uncommon there. In short, these lesions favor sun-exposed skin.