Robert J Pignolo1, Blythe P Durbin-Johnson2, David M Rocke3, Frederick S Kaplan4. 1. Department of Medicine, Mayo Clinic School of Medicine, Mayo Clinic, Rochester, MN, United States. Electronic address: pignolo.robert@mayo.edu. 2. Department of Public Health Sciences, School of Medicine, Department of Biomedical Engineering, University of California, Davis, CA, United States. Electronic address: bpdurbin@ucdavis.edu. 3. Department of Public Health Sciences, School of Medicine, Department of Biomedical Engineering, University of California, Davis, CA, United States. Electronic address: dmrocke@ucdavis.edu. 4. Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; The Center for Research in FOP and Related Disorders, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States. Electronic address: frederick.kaplan@uphs.upenn.edu.
Abstract
BACKGROUND: Fibrodysplasia ossificans progressiva (FOP) causes progressive disability due to heterotopic ossification from episodic flare-ups. Using data from 500 FOP patients (representing 63% of all known patients world-wide), age- and joint-specific risks of new joint involvement were estimated using parametric and nonparametric statistical methods. RESULTS: Compared to data from a 1994 survey of 44 individuals with FOP, our current estimates of age- and joint-specific risks of new joint involvement are more accurate (narrower confidence limits), based on a wider range of ages, and have less bias due to its greater comprehensiveness (captures over three-fifths of the known FOP patients worldwide). For the neck, chest, abdomen, and upper back, the estimated hazard decreases over time. For the jaw, lower back, shoulder, elbow, wrist, fingers, hip, knee, ankle, and foot, the estimated hazard increases initially then either plateaus or decreases. At any given time and for any anatomic site, the data indicate which joints are at risk. CONCLUSIONS: This study of approximately 63% of the world's known population of FOP patients provides a refined estimate of risk for new involvement at any joint at any age, as well as the proportion of patients with uninvolved joints at any age. Importantly, these joint-specific survival curves can be used to facilitate clinical trial design and to determine if potential treatments can modify the predicted trajectory of progressive joint dysfunction.
BACKGROUND:Fibrodysplasia ossificans progressiva (FOP) causes progressive disability due to heterotopic ossification from episodic flare-ups. Using data from 500 FOPpatients (representing 63% of all known patients world-wide), age- and joint-specific risks of new joint involvement were estimated using parametric and nonparametric statistical methods. RESULTS: Compared to data from a 1994 survey of 44 individuals with FOP, our current estimates of age- and joint-specific risks of new joint involvement are more accurate (narrower confidence limits), based on a wider range of ages, and have less bias due to its greater comprehensiveness (captures over three-fifths of the known FOPpatients worldwide). For the neck, chest, abdomen, and upper back, the estimated hazard decreases over time. For the jaw, lower back, shoulder, elbow, wrist, fingers, hip, knee, ankle, and foot, the estimated hazard increases initially then either plateaus or decreases. At any given time and for any anatomic site, the data indicate which joints are at risk. CONCLUSIONS: This study of approximately 63% of the world's known population of FOPpatients provides a refined estimate of risk for new involvement at any joint at any age, as well as the proportion of patients with uninvolved joints at any age. Importantly, these joint-specific survival curves can be used to facilitate clinical trial design and to determine if potential treatments can modify the predicted trajectory of progressive joint dysfunction.
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