Phototoxic reaction is a known feature of EPP at least in part triggered by the oxidative status, complement system activation, and mast cell response. The aim of this study was to verify some aspects involved in phototoxic reaction during a season. The complement system was evaluated by C3 assay, alternative pathway by factor-B, and classical pathway by C1q; oxidative status was tested with malondialdehyde (MDA) and mast cell by IL-10 assay. The serum samples were collected in winter and summer from 19 EPP patients and 13 controls. The reaction to sun exposure within each group was monitored without any invasive treatment. In summer, C3 and factor B were higher in patients than in controls (p = 0.002 and < 0.0001 respectively), while no change was detected for C1q. The oxidative stress was increased in summer in comparison with the control group (p = 0.04), and IL-10 an assay was normal in both seasons. The correlation between the C3 and factor-B in summer was significant. This study shows that the phototoxic reaction is not limited to the dermis but can also exert a systemic response, which could affect the general health of a patient. The knowledge of the pathophysiology of phototoxic reaction is essential for identifying new disease markers useful for improving clinical studies of known and future drugs.
Keywords: Alternative pathway; Complement system; Erythropoietic protoporphyria; Oxidative status; Phototoxic reaction.