Erythropoietic protoporphyria (EPP) is characterised by accumulation of protoporphyrin IX (PpIX) in erythrocytes. Upon illumination PpIX is released to the skin. Activation of the photoactive substance PpIX causes painful skin symptoms. This study aimed to objectively quantify individual light exposure of EPP patients in their everyday lives through spring and summer. We further aimed to establish the associations between daily symptoms and light exposure dose to photoprimed and non-photoprimed skin, use of gloves, and erythrocyte PpIX concentration. 14 Danish EPP patients participated from April through June, the period when symptoms are most frequent. Light exposure was measured using personal electronic dosimeters with sensor sensitivity comparable to the absorption spectrum of PpIX, measuring the biological effect of the light in this disease. Concurrently participants reported symptoms and use of protective gloves in a diary. Patients had a blood sample analysed for erythrocyte PpIX. The median patient was exposed to an average daily PpIX-weighted light dose of 3.8 J/cm² corresponding to approximately 15 min in the midday sun during summer in Denmark. The median patient reported symptoms on 29% and wore gloves on 11% of study days. There was a significant positive correlation between erythrocyte PpIX concentration and percentage of days wearing gloves (r = 0.65, p = 0.011), and a significant negative correlation between erythrocyte PpIX concentration and mean daily light dose on days not wearing gloves (r = −0.53, p = 0.049). Photosensitivity was strongly dependent on photopriming.

促红细胞原卟啉症（EPP）的特征是原卟啉IX（PpIX）在红细胞中积累。光照后，PpIX释放到皮肤上。光活性物质PpIX的活化会引起皮肤疼痛症状。这项研究旨在客观地量化EPP患者在整个春季和夏季的日常生活中的个人光照。我们进一步旨在建立日常症状与光敏和非光敏皮肤的光照剂量，手套的使用以及红细胞PpIX浓度之间的关联。从4月到6月，这是症状最频繁的时期，有14名丹麦EPP患者参加。使用个人电子剂量计测量曝光量，其传感器灵敏度与PpIX的吸收光谱相当，从而测量光在该疾病中的生物效应。同时，参与者在日记中报告了症状并使用了防护手套。患者的血液样本中分析了红细胞PpIX。中位患者每天平均接受PpIX加权轻剂量3.8 J / cm²对应于丹麦夏季中午大约15分钟。中位患者在研究日中有29％出现症状，在11％的时间内戴着手套。红细胞PpIX浓度与戴手套的天数百分比呈显着正相关（r = 0.65，p = 0.011），而未戴手套的红细胞PpIX浓度与日平均光剂量之间呈显着负相关（r = -0.53 ，p = 0.049）。光敏性强烈依赖于光引发。