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Actinic Keratosis

Synonym: solar keratosis

Pre-cancerous neoplasm restricted to the epidermis induced by exposure to sunlight.

Epidemiology
Prevalence 10% in ages 30-39 years rising to more than 80% with pale complexion aged 60-69 years - related to climate.
Risk Factors Blue eyes, childhood freckling, albinism and xeroderma pigmentosum. Outdoor workers. More common in men.

Presentation Clinical features develop slowly over many years, most present aged 40-60 years
Symptoms Usually asymptomatic or mildly irritating.
Signs Skin-coloured - single or multiple macule or papule(s) varying in colour from pink to yellow-black with rough scaly surface. May be better detected by feeling than seeing. Usually 1-3 mm in diameter, but up to 4 cm. Majority found on the head, neck, forearms and hands and. 5 clinical types: erythematous, keratotic papule, verrucous, papillomatous, pigmented and cutaneous horn.

Differential Diagnosis Discoid lupus erythematosus, other benign inflammatory disorders, deep fungal infections, solar elastosis and skin neoplasms eg., seborrheic keratoses and large cell acanthoma. Superficial basal cell carcinoma.

Investigations Biopsy

Management
Drugs 5-Fluorouracil cream for 2-4 weeks, 5-10% trichloroacetic acid for widespread lesions. Systemic acitretin or isotretinoin can reduce number of lesions
Surgical Cryosurgery using liquid nitrogen, electro-desiccation, curettage.

Complications May progress from cutaneous dysplasia (Squamous Cell Carcinoma grade 1/2) to a full thickness dysplasia called Bowenoid (SCC grade 1- an in situ SCC). Low risk of Actinic Keratosis lesion becoming SCC but chance increases with many lesions.

Prognosis May disappear spontaneously, but usually stay for years.

Prevention Prevention is by use of a sunscreen with protection factor 17 especially in higher risk groups, including those who are immunocompromised.

References Used

1. Schwartz RA. The actinic keratosis. A perspective and update. Dermatol Surg. 1997 Nov; 23(11):1009-19; quiz 1020-1.

Acknowledgements EMIS is grateful to doctoronline.nhs.uk for facilitating draft authoring of this article. The final copy has passed peer review of the independent Mentor GP authoring team. ©EMIS 2003.