biostudies-literatureUnknown20(1)Naik H<h4>Background</h4>Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders that can negatively affect one's health-related quality of life (HRQoL) because of pain from phototoxic reactions and the avoidance of sun exposure that is recommended. There is a need for reliable and valid patient-reported outcome measures (PROMs) that address all aspects of EPP/XLP, including symptoms and impacts. Our objective was to assess 2 recently developed PROMs, the Sunlight Exposure Diary and the EPP Impact Questionnaire (EPIQ), to determine their factor structure and explore their psychometric properties.<h4>Results</h4>During a clinical trial conducted from January 2023 to August 2024 evaluating an oral therapy to improve sunlight tolerance in adults, participants with EOrphanet journal of rare diseases492https://www.ebi.ac.uk/biostudies/studies/S-EPMC12486579biostudies-literatureValidation of the sunlight exposure diary and the erythropoietic protoporphyria impact questionnaire (EPIQ).PMC12486579Mathias SDColwell HHTurner MPO'Grady MChin MNorregaard CNaik HSavage WfalseValidation of the sunlight exposure diary and the erythropoietic protoporphyria impact questionnaire (EPIQ).<h4>Background</h4>Erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) are rare disorders that can negatively affect one's health-related quality of life (HRQoL) because of pain from phototoxic reactions and the avoidance of sun exposure that is recommended. There is a need for reliable and valid patient-reported outcome measures (PROMs) that address all aspects of EPP/XLP, including symptoms and impacts. Our objective was to assess 2 recently developed PROMs, the Sunlight Exposure Diary and the EPP Impact Questionnaire (EPIQ), to determine their factor structure and explore their psychometric properties.<h4>Results</h4>During a clinical trial conducted from January 2023 to August 2024 evaluating an oral therapy to improve sunlight tolerance in adults, participants with E2025-01-01T00:00:00Z2025 Sep2026-06-04T01:48:36.542Z2026-05-04T03:13:56.923ZS-EPMC124865794102976910.1186/s13023-025-04012-8