Longitudinal Evaluation of Pain, Flare-Up, and Emotional Health in Fibrodysplasia Ossificans Progressiva: Analyses of the International FOP Registry.

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare, inherited, connective tissue disease with ∼800 documented cases worldwide. The principal pathological feature of FOP is the transition of skeletal muscle, tendons, ligaments, and fascia into cartilage and bone. This heterotopic ossification (HO) is often preceded by painful soft tissue swellings or flare-ups that may last several months. For many individuals, experiencing a flare-up may represent a worsening of their condition and contribute to feelings of anxiety or suppressed affect, both of which are well-recognized to exacerbate pain perception. To date, much remains unknown regarding the dynamics of pain and emotional health in FOP during flare-up and also quiescent, non-flare-up disease phases. In order to elucidate the occurrence and effect of pain in FOP, this study analyzed Patient-Reported Outcomes Measurement Information System-based questionnaires completed by 99 patients participating in the international FOP Registry over a 30-month period. We observed that although moderate to severe pain (≥4, 0 to 10 pain scale) was commonly associated with flare-ups (56% to 67%), surprisingly, 30% to 55% of patients experienced similar pain levels during non-flare-up states. In those patients reporting pain levels of ≥4, 45% to 74% of patients report experiencing anxiety, depression, or irritability, with 36% to 48% reporting emotional problems during no to mild pain states. Furthermore, independent of the flare-up status, the severity of pain in FOP patients was found to be significantly anti-correlated with emotional health, physical health, and overall quality-of-life. These findings strongly suggest the need for an improved understanding of pain and emotional health in FOP during flare-up and quiescent periods. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.