Photosensitive psoriasis.

Photosensitive psoriasis is rare. The prevalence among psoriasis patients was estimated to be 5.5%. Photosensitive psoriatics have a statistically significant higher frequency of skin type I, a heredity of photosensitivity, advanced age, and psoriasis affecting hands compared with nonphotosensitive psoriatics. Half of the patients with photosensitive psoriasis have polymorphous light eruption (PLE), with psoriasis appearing as a secondary phenomenon in the PLE lesions. The other half slowly develop psoriasis after sun exposure but without preceding PLE. These reaction patterns may be confirmed with phototesting. Photochemotherapy is effective treatment for photosensitive psoriasis.