Actinic keratosis (AK) is a lesion that forms on sun-damaged skin. The lesions are small scaly patches on parts of the body, such as the face, ears, bald scalp, arms, and hands, which have been chronically exposed to the sun.
AK is a precancerous condition that affects only the top layer of skin (the epidermis). Ultraviolet (UV) rays from the sun damage the skin and if left untreated, 15% of AK can turn into a form of skin cancer called squamous cell carcinoma (SCC). When they are found early, AKs are highly treatable.
AK is more common in people with fair skin. It is found in 15% of people in North America and Europe. Australia has the highest rate of AK in the world.
UV light from the sun and commercial tanning lamps or beds are the major causes of AK. UV light causes changes in the genetic material of the skin's cells. Changes in certain genes can cause cells to grow abnormally and form lesions. There is some link between infection with human papillomavirus (HPV) and AK, but this is not yet proven.
Risk factors include:
- age 60 and older - AK can happen at any age, but the risk increases with accumulated sun exposure
- immunosuppression - the body's ability to recognize and fight abnormal cells is lowered in people with weak immune systems (e.g., as a result of taking organ transplant medications or chemotherapy, or having AIDS), so cells with gene changes are allowed to grow and form lesions
- men - they tend to work outdoors and have more sun exposure than women
- people with fair skin - also people who have red or blond hair and those who tend to burn rather than tan develop AK more easily
- sun exposure - people who work outdoors or have more exposure to the sun are at higher risk