User:Mr. Ibrahem/Actinic keratosis

Actinic keratosis (AK), also called solar keratosis, is a pre-cancerous skin lesion that may develop into squamous cell skin cancer or resolve without treatment. They often present in groups on sun-exposed parts of the head, arms, and backs of the hands. They are well-defined; red, skin coloured, or pigmented; hard or warty; smooth, shiny, or scaly bumps. Individual lesions typically range in size from 0.2 cm to 1 cm. Horns may form in the hypertrophic type. There are generally no symptoms; though if scratched, they may bleed.

The cause is long-term ultraviolet (UV) light exposure. Risk factors include being fair-skinned, greater sun exposure, poor immune function, and arsenic exposure. The underlying mechanism involves DNA damage by UV light. Diagnosis is typically based on appearance; though biopsy or excision with histologic examination may be used in unclear cases. Other conditions that may look similar include lupus, pemphigus foliaceus, erosive pustular dermatosis of the scalp, and basal cell carcinoma.

Multiple treatments are available. Cryotherapy is frequently used with cure rates of about 75%; however, may result in undesired skin lightening. Topical creams, such as 5-fluorouracil or imiquimod, may be better for large area of lesions. Photodynamic therapy (PDT) is another option for numerous lesions in a region of skin. If left untreated, 8-20% turn into squamous cell skin cancer.

Actinic keratosis is common. Males are more frequently affected than females. They become more common with age, with onset usually in those over the age of 50. With other factors being equal, it occurs more commonly near the equator. The condition was described in 1896 by William Dubreuilh. The current name dates to 1958 by Pinkus.