IL1 Inhibition in FOP

The investigators will perform an observational study on patients with FOP who have decided, along with their primary medical team, to start anti-IL1 therapy with either anakinra or canakinumab due to intractable or unusually severe FOP disease progression. The investigators will study 11 subjects aged 6-30 years old, with a self-reported flare frequency of at least 4 flares/year [2 times above the average reported FOP population flare frequency of 2 flares/year] or with an intractable flare that has lasted greater than 1 month. Subjects will begin an observational period during the medication prescription and insurance approval process and will then be followed for up to 1 year after treatment has been initiated by the medical management team. Low-dose whole-body CT (WBCT) imaging, bloodwork, patient-reported outcomes, pain, and flare activity will be assessed during this study. In addition, patients who are currently on anti-IL1 therapy, or are unable to attain anti-IL1 therapy, will be enrolled in a separate observation-only arm to collect historical data related to their experiences on therapy.

Inclusion criteria

• Patients with a clinical presentation consistent with FOP and a genetic diagnosis of classical FOP (ACVR1R206H variant) (2), male or female aged 6-30 years old.
• Patients with unusually severe FOP disease activity. This will be determined by FOP flare frequency of >4 flares per year, which is 2 times higher than the reported average in prior FOP studies ; or by a persistent flare that has failed to resolve after 1 month of standard-of-care therapy.
• Patients whose primary medical team has decided that rescue therapy with an anti-IL1 medication should be initiated. Once the primary medical team has decided that anti-IL1 therapy should be pursued, the subject will be told about this clinical-observational study and enrolled in the pre-treatment phase while access to the anti-IL1 therapy is being obtained by the clinical management team.
• Ability to participate in all assessments, including blood draws, radiology assessments, and travel. Age 6 is chosen as the lower limit to avoid the need for anesthesia for whole body CT in younger subjects.
• No history of unexplained infections, known autoimmune disease, or contraindication to anti-IL1 therapy.
• Written informed consent (and assent when applicable) obtained from subject or subject's legal representative and ability for subject to comply with the requirements of the study.

Exclusion criteria

• Pregnant, breastfeeding, or unwilling to practice birth control during participation in the study.
• Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data.
• Inability to travel to site for assessments
• Pre-existing autoimmune or autoinflammatory disease (aside from FOP)
• Inability to tolerate assessments (such as phlebotomy)
• Unexplained infections
• Current participation in an interventional trial, or study of a potentially disease modifying medication
• Inability to take medications as prescribed by managing physician