The PUVA lentigo: an analysis of predisposing factors.

Pigmented macules appearing in sun-protected sites of psoriatic patients treated chronically with oral methoxsalen photochemotherapy (PUVA) have been characterized as a lentiginous proliferation of relatively large, sometimes cytologically atypical, melanocytes (i.e., PUVA lentigines). In 1380 psoriatic adults followed prospectively, PUVA lentigines of any degree (slight, moderate, or extensive) were noted on the buttocks of 53% of patients at the most recent examination (an average of 5.7 years after starting PUVA). The frequency of moderate or extensive buttock lentigines at the most recent examination was positively associated with a greater number of PUVA treatments, an older age at starting PUVA, and male sex, and negatively associated with skin types V and VI. Moderate or extensive buttock lentigines were present in 17% of 693 patients who had not had PUVA for 1-2 years or longer. According to a regression analysis, the persistence of buttock lentigines was related in greatest measure to the total number of PUVA treatments received and was relatively independent of the time interval from the last PUVA treatment to the most recent examination or to "other" UV radiation therapy (predominantly UVB) received after PUVA was discontinued. Until the long-term course of PUVA lentigines is known, individuals who develop "fixed" pigmented lesions while on PUVA should be monitored continually for melanocytic dysplasias, including melanoma.