Prospective Clinical Assessment Study in Adolescents and Adults With Erythropoietic Protoporphyria (EPP) and X-Linked Porphyria (XLP) (STEPP)
The purpose of this study is to collect information about the effects of EPP/XLP in adults and adolescents. This is an observational study in which participants will not receive any treatment. Study details include: * The study duration will be up to 6 months for each participant. * After Screening, participants will have a Baseline (Day 1) visit and return for visits every 4 weeks through 24 weeks. * Assessments to evaluate EPP/XLP will include clinical laboratory tests, physical exams, vital signs measurement, blood draws for PPIX concentration, reporting of EPP/XLP-related symptoms (including completion of a daily diary), light dosimetry.
• Aged 12 years and older.
• Confirmed diagnosis of EPP or XLP as follows:
‣ Genetic confirmation of EPP (FECH mutation with reduced ferrochelatase activity) OR
⁃ Genetic confirmation of XLP (ALAS2 gain-of-function mutation) OR
⁃ Elevated free PPIX levels in RBCs consistent with EPP/XLP, supported by clinical and/or family history.
• Currently has symptoms of EPP/XLP.
• History of consistent, non-painful prodrome within approximately 45 minutes of sunlight exposure and prior to phototoxic attacks, as self-reported by the participant.
• Willing and able to wear a light dosimetry device during the study.
• Willing and able to complete a daily diary of EPP/XLP symptoms.
• Willing and able to keep skin sites chosen for provocative sunlight exposure testing covered by opaque material when outside or exposed to potentially triggering light beginning 2 days prior to testing.
• Willing and able to provide informed consent and/or assent for the study.
• Study participants and LAR (as appropriate) are willing and able to comply with study visits and study procedures.