OBJECTIVES: Fibrodysplasia ossificans progressiva (FOP; OMIM #135100) is an ultra‑rare genetic disorder in which heterotopic ossification causes severe, irreversible disability. We present results from an international FOP burden of illness survey (NCT04665323) assessing joint function, quality of life (QoL), and use of aids, assistive devices, and adaptations (AADAs) by age.

METHODS: Individuals with FOP completed the online survey (proxy-completed for <13 years) from 18Jan21–30Apr21. The FOP‑Physical Function Questionnaire (FOP‑PFQ) assessed physical functioning (total scores transformed to percentages of worst total score; lower scores indicate better functioning). The Patient-­Reported Outcomes Measurement Information System (PROMIS) assessed QoL (<15 years: total score; ≥15 years: global physical/mental health scores; all converted into T‑scores; higher scores indicate better health). AADAs were categorized by: mobility/daily activities/pay for assistance; bathroom/bedroom/home; workplace/technology; school/sport. Descriptive analyses were conducted by age group (years): <8; 8–14; 15–24; ≥25.

RESULTS: 219 patients/proxies responded to the survey (years): <8, n=31; 8–14, n=40; 15–24, n=40; ≥25, n=108. Mean (standard deviation [SD]) FOP‑PFQ percentage of worst total score for patients <8/≥25 years was 29.6 (25.1)/76.1 (26.7). Mean (SD) PROMIS T-score for patients <8/8–14 years was 43.4 (7.5)/41.8 (10.9). Patients ≥25 years had lower mean (SD) PROMIS T‑scores than patients 15–24 years: physical health, 35.8 (8.6) versus 42.7 (8.0); mental health, 43.5 (9.5) versus 49.0 (8.5). Mean (SD) AADAs for patients <8/≥25 years were: mobility, daily activities, and pay for assistance, 1.1 (1.4)/3.2 (1.1); bathroom, bedroom, and home, 1.0 (1.1)/2.3 (0.9); workplace and technology, 0.4 (0.8)/1.0 (0.8); school and sport, 1.1 (0.8)/0.8 (0.8).

CONCLUSIONS: Older patients with FOP had reduced physical functioning, lower QoL related to physical health, and higher AADA use than younger patients. These cross‑sectional data demonstrate the cumulative disability observed in patients with FOP and that the physical impact of FOP increases substantially with age.