Actinic Keratosis
Solar keratosis, Keratosis senilis.
This shows the typical crusty appearance of an actinic keratosis. Note the signs of sun damage to the surrounding skin.
Features
Actinic keratoses are defined as hyperkeratotic lesions occurring in sun-exposed adult skin, which carry a low risk of progression to invasive squamous cell carcinoma. This risk has been estimated at roughly 1% per annum.
The lesions initially start as telangiectatic capillaries, which go unnoticed by most patients. After this, a well adherent yellow/brown scale forms over the site of the telangiectasia. The scale becomes rougher, thicker and hornier over time. The most common sites of these lesions are in sun exposed areas such as the backs of the hands, forearms and the face. The sides of the neck (see Figure 1) and upper ear are also common sites of the lesions. Lesions are usually multiple, with most patients not having one but usually 10-20 actinic keratoses.
Incidence
Actinic keratoses are extremely common. The highest incidence is in Australia, where 40-50% of all white adults over 40 have actinic keratoses. They are more common in men than women.
Aetiology
Actinic keratoses are caused by excessive exposure to sunlight (and therefore UV radiation). Risk factors include: increasing age, proximity to the equator, fair skin (skin types 1 or 2), outdoor activities or occupation and a diet high in animal fats.
Differential Diagnosis
Squamous cell carcinoma. Lentigo maligna.
Treatment
Patients should be given advice about wearing a hat, sunscreen and avoiding being out in the sun between the hours of 11am and 3pm. Recent evidence has shown that this may cause the lesions to regress, and will decrease the likelihood of further lesions forming.
Treatment of existing actinic keratoses can be with cryotherapy or 3% diclofenac (Solaraze). Topical preparations of 5-fluorouracil (Efudix) can also be used. If in doubt, excision of the lesion followed by histology may be indicated.
