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AT-A-GLANCE
A rare chronic pruritic and excoriated papular or nodular eruption of sun-exposed and, to a lesser extent, nonexposed skin.
Beginning in childhood, it may remit at puberty, exacerbate most often in summer, and fade in winter.
Indigenous peoples of North and South America are disproportionately affected.
Association with HLA-DR4, specifically the HLA- DRB1*0407 and DRB1*0401 variants
Prevention through avoidance of sunlight is the first-line therapy; thalidomide or other immunosuppressive agents may be required.
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Actinic prurigo (AP) is a chronic sunlight-induced pruritic eruption characterized by papules or nodules, many of which are excoriated. Lesions are distributed mostly on sun-exposed skin but may also occur in sun-protected sites. A family history of the disease may be reported by patients. Indigenous peoples of the Americas are most often affected, and strong associations with specific human leukocyte antigen (HLA) types have been identified.
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HISTORICAL PERSPECTIVE
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AP was first described by Hutchinson in 1878 and was designated by him as “summer prurigo.” Other historical terms for the disease include solar eczema, prurigo solar, hereditary polymorphic light eruption, and hydroa aestivale.1
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AP occurs throughout much of the world. The indigenous populations of North and South America are particularly affected. The disease is estimated to occur in 2% of the Canadian Inuit population.2 In Mexico, AP is seen most commonly in the indigenous and Mestizo (mixed native and European descent) populations living at altitudes greater than 1000 m.3 Less commonly, inhabitants of Europe, United States, Australia, and Asia are reported to develop AP. In Scotland, less than 1% of all patients evaluated in a specialized photodiagnostic unit were diagnosed with AP.4
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In most populations, females are affected more frequently than males, in a ratio ranging from 2:1 to 4:1.5 In Asians, there is a male predominance.6 The eruption has its onset in childhood, usually present by age 10 years.7 The onset of disease appears to occur earliest in Native American populations, at 4 to 5 years of age.5 A positive family history of either AP or polymorphous light eruption is present in about a fifth of patients.8
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The eruption is often present all year round, but it is commonly worse in summer. About one third of patients experience symptoms in wintertime.9 Very rarely it is worse in winter, with immunologic tolerance presumably developing during the summer. Exacerbations tend to begin gradually during sunny weather in general rather than after specific sun exposure, although PMLE-like outbreaks may also occur. Patients may not be aware that lesions are provoked by sun exposure.
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Pruritus is universally present and is typically severe.5,10 Pain or ...