The natural history of fibrodysplasia ossificans progressiva: A prospective, global 36-month study
Robert J. Pignolo, Geneviève Baujat, Matthew Brown, Carmen De Cunto, Edward C. Hsiao, Richard Keen, Mona Al Mukaddam, Kim‐Hanh Le Quan Sang, Amy C. Wilson, Rose Marino, Andrew Strahs, Frederick S. Kaplan
Abstract
Purpose We report the first prospective, international, natural history study of the ultra-rare genetic disorder fibrodysplasia ossificans progressiva (FOP). FOP is characterized by painful, recurrent flare-ups, and disabling, cumulative heterotopic ossification (HO) in soft tissues. Methods Individuals aged ≤65 years with classical FOP ( ACVR1 R206H variant) were assessed at baseline and over 36 months. Results In total, 114 individuals participated; 33 completed the study (mean follow up: 26.8 months). Median age was 15.0 (range: 4-56) years; 54.4% were male. During the study, 82 (71.9%) individuals reported 229 flare-ups (upper back: 17.9%, hip: 14.8%, shoulder: 10.9%). After 84 days, 14 of 52 (26.9%) imaged flare-ups had new HO at the flare-up site (mean new HO volume: 28.8 × 10 3 mm 3 ). Mean baseline low-dose whole-body computed tomography (excluding head) HO volume was 314.4 × 10 3 mm 3 ; lowest at 2 to <8 years (68.8 × 10 3 mm 3 ) and increasing by age (25-65 years: 575.2 × 10 3 mm 3 ). The mean annualized volume of new HO was 23.6 × 10 3 mm 3 /year; highest at 8 to <15 and 15 to <25 years (21.9 × 10 3 and 41.5 × 10 3 mm 3 /year, respectively) and lowest at 25 to 65 years (4.6 × 10 3 mm 3 /year). Conclusion Results from individuals receiving standard care for up to 3 years in this natural history study show the debilitating effect and progressive nature of FOP cross-sectionally and longitudinally, with greatest progression during childhood and early adulthood.