Actinic keratosis (AK, also known as solar keratosis) is a cutaneous lesion that results from the proliferation of atypical epidermal keratinocytes. AKs represent early lesions on a continuum with squamous cell carcinoma (SCC) and occasionally progress to SCC.
AKs often present as erythematous and scaly macules or papules; lesions are most commonly detected in adults with fair skin. Chronic sun exposure is a major risk factor for the development of these lesions, which accounts for the usual detection of AKs in frequently sun-exposed areas (eg, balding scalp, face, lateral neck, and distal upper or lower extremities).
The epidemiology, clinical features, natural history, and diagnosis of AK will be discussed here. The management of AK and SCC is reviewed elsewhere. (See "Treatment of actinic keratosis" and "Epidemiology and risk factors for cutaneous squamous cell carcinoma" and "Clinical features and diagnosis of cutaneous squamous cell carcinoma (SCC)" and "Treatment and prognosis of cutaneous squamous cell carcinoma".)
EPIDEMIOLOGY AND RISK FACTORS
In the United States, AKs are among the most common reasons for visits to dermatologists [1-4]. It is estimated that between 1990 and 1999, 14 percent of dermatology visits in the United States were related to AKs .
Individuals with fair skin are most likely to develop AKs, and much of the data on the epidemiology and risk factors for AK are derived from studies in Australia, northern Europe, and the United States. Factors such as the extent of exposure to ultraviolet light and certain phenotypic features have been associated with risk for developing these lesions.