Experimental and approved treatments for skin photosensitivity in individuals with erythropoietic protoporphyria or X-linked protoporphyria: A systematic review

Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are characterized by skin photosensitivity caused by accumulation of protoporphyrin IX. We aimed to review the clinical evidence of efficacy and safety of skin photosensitivity treatments in individuals with EPP or XLP. We systematically searched MEDLINE, Embase, the Cochrane Library, and ClinicalTrials.gov. A total of 40 studies with data on 18 treatment modalities were included. Comprehensive treatment safety data were obtained from the European Medicines Agency and the United States Food and Drug Administration. The studies used different outcome measures to evaluate the sensitivity without a generally accepted method to assess treatment effect on skin photosensitivity. Of the included studies, 13 were controlled trials. Gathered, the trials showed moderate positive effect of inorganic sunscreen application and subcutaneous implant of afamelanotide and no effect of organic sunscreen application, or oral treatment with beta-carotene, cysteine, N-acetylcysteine, vitamin C, or warfarin. Studies without control groups suggested treatment effect of foundation cream, dihydroxyacetone/lawsone cream, narrow-band ultraviolet B phototherapy, erythrocyte transfusion, extracorporeal erythrocyte photodynamic therapy, or oral treatment with zinc sulphate, terfenadine, cimetidine, or canthaxanthin, but the real effect is uncertain. Assessment of treatment effect on photosensitivity in patients with EPP or XLP carries a high risk of bias since experienced photosensitivity varies with both weather conditions, exposure pattern, and pigmentation. Controlled trials of promising treatment options are important although challenging in this small patient population.