Actinic Prurigo

Seen here are a 38-year-old Native American woman and her 20-year-old daughter, each of whom has had a relapsing eruption for several years. Pruritic, red to red-brown plaques develop on their faces and necks and on the dorsal surface of their hands. Scattered brown and hypopigmented macules as well as some scaling and slight erythema appear on their lower lips. The women stated that the eruptions flare each spring and gradually improve throughout the rest of the year. The daughter's lesions were more acute at this time and had developed during the preceding 3 days.

The diagnosis was actinic prurigo. This uncommon, idiopathic photodermatosis mainly affects Native Americans, among whom it is known specifically as hereditary polymorphous light eruption of American Indians. Affecting about three times as many females as males, this papular or nodular eruption occurs predominantly on sun-exposed areas. The rash may occur to a lesser extent on nonexposed areas, and conjunctivitis may be observed in up to half of all cases.

Actinic prurigo often develops during childhood; although it may improve or resolve in early adulthood, it frequently becomes a chronic condition. It is most severe during the summer, but flares may occur year-round. Because it is so itchy, excoriation and/or eczematization of the lesions may result, and scarring can occur. The diagnosis is clinical; thus, always consider the possibility of other photodermatoses, and screen patients for systemic lupus erythematosus and porphyria.

The primary treatment for actinic prurigo consists of restricting sun exposure with use of a broad-spectrum sunscreen that provides both UVA and UVB protection, write Drs Eric J. Lewis, Charles E. Crutchfield III, and Michael J. Ebertz of Minneapolis. Oral antihistamines and emollients may offer additional symptomatic relief from the persistent itching. Other modalities that have been used include topical corticosteroids, psoralen UVB or psoralen plus UVA (PUVA) phototherapy, high doses of β-carotene, antimalarial drugs, and-in intractable cases-thalidomide.

FOR MORE INFORMATION:

• Fusaro RM, Johnson JA. Hereditary polymorphic light eruption of American Indians: occurrence in non-Indians with polymorphic light eruption. J Am Acad Dermatol. 1996;34:612-617.
• Hojyo-Tomoka T, Vega-Memjie E, Granados J, et al. Actinic Prurigo: an update. Int J Dermatol. 1995;34:380-384.
• Lane PR, Hogan DJ, Martel MJ, et al. Actinic Prurigo: clinical features and prognosis. J Am Acad Dermatol. 192;26:683-692