Seasonal variations in erythropoietic protoporphyria patients' responses about sun behaviour, symptoms, and treatment effect.

Patients with erythropoietic protoporphyria (EPP) have highly variable, increased levels of erythrocyte protoporphyrin IX (PpIX). Upon exposure to visible light, the PpIX is released from the erythrocytes to the skin, producing phototoxic reactions. Severe photosensitivity heavily impacts the patients' daily behavior regarding sun exposure and outdoor life. As patients with EPP in Northern European countries may be free of symptoms during winter, their individual evaluation of sun behavior in summer, the severity of summer symptoms, and effect of oral treatment with Cimetidine and/or zinc sulphate may vary greatly depending on season when answering our EPP DLQI questionnaire. Nineteen patients with EPP answered questions in both mid-summer and the following mid-winter, respectively. The patients' sun behavior was identical when asked both summer and winter. Symptoms were reported as worse in winter than in summer. Treatment effect on symptoms was reported as better in summer than recalled when patients were asked the same question in winter. Erythrocyte PpIX decreased by 14 µmol/L during treatment. These observations may help the clinician decide when to schedule follow-up consultations for patients with EPP.