Participants must have a confirmed diagnosis of FOP and the participant (or a parent or legal guardian) must be willing and able to provide written informed consent. There are no exclusion criteria. Data collected in the Patient Portal include: patient demographics and diagnosis pathway; medical and dental care; clinical research participation and biospecimen donation; heterotopic ossification (bone growth and episodic flare-ups); other signs and symptoms by body system; patient-reported outcomes (physical functioning, pain, fatigue, and general health); and assistive devices, aids, attendants, and adaptations. Because the Registry is designed to accommodate participants along a broad spectrum of FOP disease severity, most of the data fields are optional, allowing participants a high degree of flexibility in how much information they contribute, which also minimizes participant burden.