Disseminated Superficial Actinic Porokeratosis on Legs

A 48-year-old man requested medical evaluation of the multiple spots that gradually appeared on his legs over the past 5 years. The clinical diagnosis of disseminated superficial actinic porokeratosis (DSAP) was confirmed histopathologically.

Drs Charles E. Crutchfield III and Humberto Gallego of St Paul write that DSAP is a common form of porokeratosis that can occur sporadically or is inherited via an autosomal dominant mode. It occurs slightly more often in women than men and usually erupts in the third or fourth decade of life as multiple (typically, more than 50), small (1 to 3 cm), red patches and plaques with a distinctive keratotic border. Frequently, the central portions of the lesions are atrophic and scaly.

This disorder occurs almost exclusively on sun-exposed extremities, and sunlight may exacerbate the condition. DSAP also can be induced by psoralen plus ultraviolet light of A wavelength (PUVA) therapy. An increased prevalence of DSAP has been reported among immunosuppressed persons.

The porokeratoses represent a group of cutaneous disorders with a common histopathologic feature: the cornoid lamellae. Cornoid lamellae are columns of parakeratosis that correspond clinically to the raised hyperkeratotic border with a closely associated furrow. Cornoid lamellae may represent a clone of keratinocytes that have an increased rate of proliferation and/or premature keratinization.

Because of the risk of malignant degeneration over a lifetime (approximately 5%), removal or destruction of the lesions is indicated. Cryotherapy, superficial surgery, and topical 5-fluorouracil have been used successfully.

FOR MORE INFORMATION:

• Dover JS, Jackson BA. Pocket Guide to Cutaneous Medicine and Surgery. Philadelphia: WB Saunders Company; 1996.

• Orkin M, Maibach HI, Dahl MV. Dermatology. Norwalk, conn: Appleton & Lange; 1991:257-285.