Polymorphous light eruption

The polymorphous light eruptions are idiopathic photodermatoses characterized by various clinical patterns ranging from small papules and papulovesicular lesions to large papules that coalesce to form plaques. The eruptions may begin at any time of life from young childhood to old age, and any race may be afflicted. However, they are particularly prevalent in the North American and Latin American Indian and the Finnish populations. In these two populations there appears to be a genetic (dominant) predisposition to develop the problem. The results of phototesting procedures indicate that the UVB rays make up the action spectrum for reproducing the lesions. However, some patients react to UVA wavelengths as well, and two reports suggest that certain patient populations will react abnormally only to UVA rays. The mechanism of the response is unclear, although the clinical picture, delayed reaction time, and histology suggest that at least some of these responses are due to a cell-mediated hypersensitivity reactivity. Therapy varies with degrees of sensitivity. Protection with clothes, strong sunscreens, and avoidance of the noonday sun may be essential for exquisitely sensitive patients. Topical and systemic corticosteroids may be needed for acute exacerbations. Systemically the 4-aminoquinoline antimalarial drugs are quite effective for less sensitive patients with the large papule and plaque variety. Thalidomide has proved to be most effective in the American Indian form of the disease, and PUVA has been found to be most effective in treating and preventing the process in even very sensitive patients. Most recently, the systemic use of Imuran has proved to be of great value in middle- to older-aged individuals with a severe eczematous form of the disease.