Prospective observational pilot study of quantitative light dosimetry in erythropoietic protoporphyria

Observational pilot study of multi-wavelength wearable light dosimetry for erythropoietic protoporphyria

BACKGROUND

Erythropoietic protoporphyria (EPP) causes painful light sensitivity, limiting quality of life. Our objective was to develop and validate a wearable light exposure device and correlate measurements with light sensitivity in EPP to predict and prevent symptoms.

METHODS

A wearable light dosimeter was developed to capture light doses of UVA, blue, and red wavelengths. A prospective observational pilot study was performed in which five EPP patients wore two light dosimeters for 3 weeks, one as a watch, and one as a shirt clip.

RESULTS

Standard deviation (SD) increases from the mean in the daily blue light dose increased the odds ratio (OR) for symptom risk more than the self-reported outdoor time (OR 2.76 vs. 2.38) or other wavelengths, and a one SD increase from the mean in the daily blue light wristband device dose increased the OR for symptom risk more than the daily blue light shirt clip (OR 2.45 vs. 1.62). The area under the receiver operator curve for the blue light wristband dose was 0.78, suggesting 78% predictive accuracy.

CONCLUSION

These data demonstrate that wearable blue light dosimetry worn as a wristband is a promising method for measuring light exposure and predicting and preventing symptoms in EPP.

Update on the Porphyrias

The porphyrias are a group of rare diseases, each resulting from a defect in a different enzymatic step of the heme biosynthetic pathway. They can be broadly divided into two categories, hepatic and erythropoietic porphyrias, depending on the primary site of accumulation of heme intermediates. These disorders are multisystemic with variable symptoms that can be encountered by physicians in any specialty. Here, we review the porphyrias and describe their clinical presentation, diagnosis, and management. We discuss novel therapies that are approved or in development. Early diagnosis is key for the appropriate management and prevention of long-term complications in these rare disorders.

How I treat erythropoietic protoporphyria and X-linked protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited cutaneous porphyria caused by reduced expression of ferrochelatase, the enzyme that catalyzes the final step in heme biosynthesis. The resultant accumulation of protoporphyrin IX leads to severe, painful cutaneous photosensitivity, as well as potentially life-threatening liver disease in a small percentage of patients. X-linked protoporphyria (XLP) is clinically similar to EPP but results from increased activity of δ-aminolevulinic acid synthase 2, the first step in heme biosynthesis in the bone marrow, and also causes protoporphyrin accumulation. Although historically the management of EPP and XLP (collectively termed protoporphyria) centered around avoidance of sunlight, novel therapies have recently been approved or are in development, which will alter the therapeutic landscape for these conditions. We present 3 patient cases, highlighting key treatment considerations in patients with protoporphyria, including (1) approach to photosensitivity, (2) managing iron deficiency in protoporphyria, and (3) understanding hepatic failure in protoporphyria.

Phototesting in erythropoietic protoporphyria trials: A systematic review

Severe skin pain when exposed to long wave ultraviolet radiation or visible light is the main symptom of erythropoietic protoporphyria (EPP). Treatment options for EPP are inadequate and new treatments are needed but hampered by the lack of valid efficacy outcomes. Phototesting with well-defined illumination of the skin can be performed reliably. We aimed to provide an overview of phototest procedures used to evaluate EPP treatments. Systematic searches of Embase, MEDLINE and the Cochrane Library were performed. Searches identified 11 studies using photosensitivity as efficacy outcome. The studies used eight different phototest protocols. Illuminations were performed with a filtered high-pressure mercury arc, or a xenon arc lamp equipped with monochromator or filters. Some used broadband, others narrowband illumination. In all protocols phototests were performed on the hands or the back. Endpoints were minimal dose required to induce either first symptom of discomfort, erythema, urticaria or intolerable pain. Other endpoints were change in erythema intensity or diameter of any type of flare after exposure compared to before. In conclusion, protocols displayed extensive variability in illumination set-up and evaluation of phototest reactions. Implementation of a standardized phototest method will allow more consistent and reliable outcome evaluation in future therapeutic research of protoporphyric photosensitivity.

Light-Related Cutaneous Symptoms of Erythropoietic Protoporphyria and Associations With Light Sensitivity Measurements

Importance

Erythropoietic protoporphyria (EPP) is a rare and underdiagnosed genetic disease characterized by painful sensitivity to light. A better understanding and characterization of its light-induced cutaneous symptoms may aid in the identification of EPP in patients.

Objectives

To describe the cutaneous symptoms of erythropoietic protoporphyria (EPP) and to determine if these symptoms are associated with the degree of light sensitivity.

Design, Setting, and Participants

This was a cross-sectional study of adolescent and adult (≥15 years) patients with EPP across the US conducted by a single academic hospital via a remotely administered survey, measurements of light sensitivity by light dosimetry and by text message symptom assessments. Data analyses were conducted from November 2020 to April 2022.

Exposures

Sunlight exposure.

Main Outcomes and Measures

Self-reported symptoms and association with measured light sensitivity.

Results

The study sample consisted of 35 patients with EPP (mean [SD] age, 39.1 (15.5) years; 21 [60%] female; 14 [40%] male; 35 [100%] White individuals). The patients' median [range] skin tone was 3.0 (1.0-8.0), based on self-reporting from 1 (lightest) to 12 (darkest). A total of 24 participants completed the light dosimeter measurements. Phototoxic reactions were characterized by pain (97%; 34 patients), burning (97%; 34), tingling (97%; 34), pruritus (83%; 29), allodynia (89%; 31), improvement of symptoms with cold (89%; 31), achiness (24%; 12), fatigue (46%; 16), mild swelling (83%; 29), severe swelling (63%; 22), erythema (51%; 18), petechiae (40%; 14), skin cracking (43%; 15), scabbing (46%; 16), scarring (66%; 23), and other chronic skin changes (40%; 14). Patients with EPP reported that their hands, feet, and face were most sensitive to light and that their shoulders and legs were least sensitive; 25.7% (9 patient) reported no chronic skin changes, and 5.7% (2 patients) reported never having had any visible symptoms. None of these findings varied with the degree of light sensitivity except that lower overall light sensitivity was associated with lower ranked sensitivity of the neck and arms.

Conclusions and Relevance

The findings of this cross-sectional study suggest that patients with EPP have distinctive cutaneous symptoms that may aid in identification of this underdiagnosed disease. Characteristic EPP symptoms include light-induced cutaneous burning pain and occasional swelling, particularly over the hands, with a prodrome of pruritus and paresthesias. Minimal skin changes or the absence of visible skin changes during reactions to light, including lack of erythema, do not exclude an EPP diagnosis nor suggest low EPP disease burden.

Protection against visible light by dihydroxyacetone in erythropoietic protoporphyria

BACKGROUND

Patients with erythropoietic protoporphyria (EPP) are hypersensitive to long wave ultraviolet (UVA) radiation and visible light and they experience severe skin pain by light exposure. The patients have very limited treatment options. Sunless skin tanning with dihydroxyacetone (DHA) is now being investigated as a possible treatment modality of skin photosensitivity in EPP.

METHODS

We simulated the theoretical light protection factor provided by DHA application. In addition, we present 19 cases with EPP who were treated at our department with DHA weekly during spring and summer from 2018 to 2021 inclusive.

RESULTS

The protection factor against UVA and visible light was estimated to approximately two. Out of the 19 patients with EPP who were treated with DHA in 2018, 11 patients experienced a sustained good effect and continued to use the treatment on a weekly basis in the spring and summer of 2019, 2020, and 2021.

CONCLUSION AND PERSPECTIVES

Both the theoretical estimates and the uncontrolled study suggest that sunless tanning with DHA reduces photosensitivity in patients with EPP. Our hypothesis is that skin treated with DHA can tolerate twice the daylight dose compared to untreated skin before onset of skin symptoms. To validate this conclusion, we plan a randomized clinical trial to determine the effect of DHA application to reduce photosensitivity in patients with EPP under controlled clinical conditions. The study protocol for this trial is presented in the paper.