RecruitingA Study to Document and to Further Describe Long-term Safety and Effectiveness of Palovarotene in Participants With Fibrodysplasia Ossificans Progressiva (FOP)The participants in this registry study will have fibrodysplasia ossificans progressiva (FOP). FOP is an ultra-rare, severely disabling disease characterized by new bone formation in areas of the body where bone is not normally present (heterotopic ossification (HO)). HO is often preceded by painful, recurrent episodes of soft tissue swelling (flare-ups). This registry study will take place in countries where the treatment, known as palovarotene, has been approved for use. Participants will either be treated with palovarotene (i.e already be receiving palovarotene as prescribed by their treating physician according to locally approved product information) or untreated with palovarotene. The main aim of this registry study will be to collect and assess real-world safety data on children and adult participants with FOP treated with palovarotene. This registry study will also describe the effectiveness of palovarotene in exposed participants, including the effect on everyday activities and physical performance. In addition, this registry study aims to descriptively compare key safety outcomes (i.e. flare-up episodes, growth outcomes, and bone fractures) between participants exposed and unexposed to palovarotene.