Photosensitive psoriasis--clinical findings and phototest results.

A total of 35 patients, 21 women and 14 men, with light-sensitive psoriasis deteriorating in summertime on solar exposure were clinically examined in detail and subjected to standardized phototest procedures. This included provocations with UVB and high dosage UVA exposures by the use of an UVASUN 3000 lamp, and also photopatch testing. All patients had long-standing psoriasis and had observed a photosensitivity from 2 to 40 years (men 11.4 yr). The photosensitivity had remained unchanged since its appearance in 21, had worsened in 13 and improved in only 1. A hardening phenomenon was noticed by 11 patients. Exacerbation of psoriasis from sun exposure was observed mostly on the back of the hands and forearms, followed in frequency by the legs, face, chest and back. No cases of other light-sensitive disorders, e.g. vitiligo, porphyrias or connective tissue diseases such as lupus erythematosus were detected. 5 patients used drugs capable of inducing photoallergy but no such reactions could be substantiated. Photopatch testing revealed no photoallergic contact reactions. Skin type distribution was normal, with no overrepresentation of skin type I-II which was registered in 26% (9/35) and skin type III-IV in 74% (26/35). 18/35 patients had a history of PMLE with a secondary evolution of psoriasis lesions. The PMLE reaction was most easily provoked by high-dosage UVA exposures (12/18). 17/35 had no history of a preceding PMLE reaction and, after provocations, new psoriasis lesions appeared successively, most easily provoked by UVB (9/17). The distribution of skin types was about the same in the two groups.