Observational Study of Adults and Adolescents With Erythropoietic Protoporphyria (EPP) and X-linked Porphyria (XLP)

Inclusion criteria

• 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.

Exclusion criteria

• Diagnosis of another porphyria or another photodermatosis that may confound the characterization of EPP/XLP.
• Has a clinically significant disease or condition that, at the discretion of the Investigator or Sponsor, would interfere with the evaluation of EPP/XLP or study participation, or would make study participation not in the best interest of the participant.
• Is taking, or has taken within 60 days of Day 1, any medication, vitamin, or supplement that alters sensitivity to light exposure (eg, afamelanotide, melanotan, beta carotene, dersimelagon, or bitopertin).
• Concurrent or anticipated participation in an interventional clinical trial during the study period.