Instituto de Óptica “Daza de Valdés”

Prospective observational pilot study of quantitative light dosimetry in erythropoietic protoporphyria


  • Erythropoietic protoporphyria (EPP) deteriorates quality of life because patients must limit light exposure to avoid painful phototoxic skin reactions.

  • This pilot study explores the use of a light dosimeter to measure light exposure and provides an initial description of the relationship between daily light dose and symptoms and explores novel strategies to measure light tolerance.

  • A device for measuring the received light dose it is a more accurate way to measure light tolerance and better estimate symptom risk than self-report time outdoors for patients with erythropoietic protoporphyria.

Madrid / 9 de March de 2023

A team of scientists from the United States and Spain has conducted a pilot study, published in the Journal of the American Academy of Dermatology, to explore the relationship between light exposure and symptoms in people with erythropoietic protoporphyria (EPP). in English). The study showed that an ultraviolet light dosimeter was more accurate in measuring light tolerance and predicting symptom risk than self-reporting of time outdoors by patients. The results of this study will help scientists develop methods to predict and prevent symptoms in patients with this disease, thereby improving their quality of life.
Fig. 1 a: Acute photosensitivity reaction on the back of the hand in PPE (image taken from [1]), b UV light detectors, such as the SunSense Pro used in this study, are small devices that can get snagged to outer clothing. Information on cumulative sun exposure and sun intensity can be accessed (image taken from [2]), c Device dosimetry measurements, but not self-reported outdoor times, correlate with light tolerance self-reported by patients with EPP.
Erythropoietic protoporphyria is a rare genetic disorder that affects the skin, causing it to become sensitive to light (Fig. 1a). People with PPE must limit their exposure to light or else they may experience severe and painful phototoxic reactions.
Clinical trials on PPE have been limited by the use of imprecise endpoints that depend on patients self-reporting time spent outdoors, and there are currently no reliable methods to predict and prevent symptoms of the disease.
To address this issue, a pilot study was conducted with 24 patients with PPE. Participants completed a survey about their sensitivity to light, wore an ultraviolet light dosimeter (fig. 1b) for one month, and sent their outdoor times by text message for another month. Throughout, participants reported any PPE-related symptoms they experienced. The study found a correlation between daily light dose from the dosimeter and their degree of light tolerance, but not for each patient’s light tolerance and self-reported exposure measurements (fig. 1c).
Both device dose and patient-reported time outdoors were associated with symptoms, but a stronger association was observed with device dose. A one standard deviation increase from the mean in light dose measured by dosimetry increased the odds of having symptoms by 70%.
In addition, a one standard deviation increase in the previous day’s device dose increased the odds of symptoms by 14%, providing a new quantification of the priming effect of EPP.

The study concluded that device dosimetry provides a better measure of PPE patients’ light tolerance and a better estimate of symptom risk compared with self-reported time outdoors.
This study provides an important foundation for future studies of light dosimetry in PPE, which could be used to inform clinical trial endpoints, as well as to predict and prevent PPE symptoms.

Full publication reference (also available at Dickey, A.K., Rebeiz, L., Raef, H., Leaf, R.K., Elmariah, S., Naik, H., Anderson, K., Conley, J ., Iyasere, C., Zhao, S. and Birkenfeld, J.S., 2022. Prospective observational pilot study of quantitative light dosimetry in erythropoietic protoporphyria. Journal of the American Academy of Dermatology.

What is Erythropoietic Protoporphyria?

Erythropoietic protoporphyria is a type of porphyria. Porphyrias are caused by an abnormality in the production process of a protein called heme that is part of various parts of the body, including red blood cells.
Erythropoietic protoporphyria can cause extreme sensitivity to sunlight, liver damage, abdominal pain, gallstones, and an enlarged spleen.

This is a research result of a team formed by the Massachusetts General Hospital Department of Medicine, the Harvard Medical School, The Boston General Hospital Healthcare Transformation Lab, the Boston General Hospital Department of Dermatology, the Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, Department of Internal Medicine, LA University of Texas, Boston General Hospital Department of Emergency Medicine, Analitica Now from Massachusetts etts, the Institute of Optics “Daza de Valdés” of the CSIC, the MIT linQ Institute of Medical Sciences and Engineering, nQ Medical of Massachusetts, the Maryland Association of United Porphyrias, and the Children’s Hospital Boston Department of Pathology

[1] Lecha, Mario, Hervé Puy, and Jean-Charles Deybach. “Erythropoietic protoporphyria.” Orphanet journal of rare diseases 4.1 (2009): 1-10.
[2] (date of access: 8.03.2023)

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