Erythropoietic Protoporphyria (EPP)

The goal of this expanded access program is to provide bitopertin to patients with EPP and XLP who have no satisfactory treatment options available in the US and to learn if bitopertin is safe to treat EPP and XLP.

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.