Photopatch tests: an Italian multicentre study from 2004 to 2006.

BACKGROUND: Evaluation of possible photoallergic contact dermatitis in at-risk populations is often not undertaken, and an agreed methodology for investigation is uncommonly used. OBJECTIVES: We conducted a retrospective multicentre study to determine the prevalence of photoallergic contact dermatitis in Italy. METHODS: A total of 1082 patients with histories and clinical features suggestive of photoallergic contact dermatitis were evaluated. All the patients had undergone photopatch testing with allergens proposed for Italy as well as other substances suggested by each patient's personal history. RESULTS: 234 patients (21.6%) were positive to at least one test substance of the standard photopatch testing series or to added substances. 234 patients (21.6%) were positive to at least one substance with a total of 290 reactions. 204 of the reactions were typically photoallergic; 68 reactions were allergic and within this group 10 were photoaugmented reactions; 18 reactions were considered to be phototoxic. CONCLUSION: The predominant group of photoallergens was drugs, followed by organic UV filters and antimicrobial agents.

A case of lichenoid drug eruption associated with sildenafil citratus.

A 53-year-old man developed lichenoid lesions on the upper chest, posterior surfaces of the trunk, and abdominal region about three months before his first visit. Physical examination and laboratory findings were normal; histopathology showed vacuolar degeneration of basal keratinocytes in association with a dense lympho-histioid infiltrate arranged in a lichenoid pattern with a few melanophages and eosinophils. The fact that our patient had been irregularly taking sildenafil citratus (Viagra) led to the hypothesis of a lichenoid drug-induced eruption. Our hypothesis was confirmed by clinical resolution three weeks after discontinuation of sildenafil citratus; moreover, the patient avoided the drug for about four months, and the eruption didn't reappear. Subsequently, we performed a challenge test with the drug, and the patient developed similar lichenoid lesions. Lichenoid eruptions are rather common dermatoses that can be induced by a great number of environmental agents and are clinically but not pathogenetically well defined. We report the present case because, despite the great number of drugs that can be implicated in the development of lichenoid eruptions, the association of such dermatoses and sildenafil citratus had been described only once previously in the literature until now. Furthermore, we wish to remark on the significance of a detailed anamnestic history to make the correct differential diagnosis between lichenoid drug-induced eruptions and lichen planus. This has a great clinical importance because simple discontinuation or substitution of the drug causes lichenoid drug-induced eruption resolution.