FOP Prevalence Study Released in Orphanet Journal of Rare Diseases

FOP Prevalence is Higher Than 1 in 2 Million

In 2020 the International FOP Association (IFOPA) partnered with Drs. Ed Hsiao, Fred Kaplan and Bob Pignolo to conduct a research study to better determine the prevalence of FOP in the United States. This followed a prevalence study conducted by Dr. Genevieve Baujat in France conducted in 2017 that identified an FOP prevalence rate of 1 per 735,000.

The IFOPA's 2020 prevalence study found the prevalence to be 0.88 per million US residents, or roughly a prevalence of 1 in 1 million. The study was published this morning, August 6, 2021, in the Orphanet Journal of Rare Diseases

We are grateful to the prevalence study sponsors: Regeneron Pharmaceuticals, Ipsen and Blueprint Medicines.

We are also grateful to the authors which include: Robert J. Pignolo, Edward C. Hsiao, Genevieve Baujat, David Lapidus, Adam Sherman and Frederick S. Kaplan.    

What does this mean for FOP patients? That FOP, while still classified as an ultra-rare disease, is more common than previously thought. The higher prevalence of FOP may attract more scientists and pharmaceutical companies to study FOP. We also hope that health care providers are more interested in learning about FOP since it is more common than previously thought.

The abstract is listed below and the full open-access manuscript can be found online. If you'd like to share this exciting news, you can share the URL

We are grateful to the FOP families living in the United States that participated in this important research survey by completing the contact survey that was sent in spring 2020. Your time and effort helped advance FOP research!


Background: Fibrodysplasia ossificans progressiva (FOP), an ultra-rare, progressive, and permanently disabling disorder of extraskeletal ossification, is characterized by episodic and painful flare-ups and irreversible heterotopic ossification in muscles, tendons, and ligaments. Prevalence estimates have been hindered by the rarity of FOP and the heterogeneity of disease presentation. This study aimed to provide a baseline prevalence of FOP in the United States, based on contact with one of 3 leading treatment centers for FOP (University of Pennsylvania, Mayo Clinic, or University of California San Francisco), the International Fibrodysplasia Ossificans Progressiva Association (IFOPA) membership list, or the IFOPA FOP Registry through July 22, 2020. 

Results: Patient records were reviewed, collected, and deduplicated using first and last name initials, sex, state, and year of birth. A Kaplan–Meier survival curve was applied to each individual patient to estimate the probability that he or she was still alive, and a probability-weighted net prevalence estimate was calculated. After deduplication, 373 unique patients were identified in the United States, 294 of whom were not listed as deceased in any list. The average time since last contact for 284 patients was 1.5 years. Based on the application of the survival probability, it is estimated that 279 of these patients were alive on the prevalence date (22 July 2020). An adjusted prevalence of 0.88 per million US residents was calculated using either an average survival rate estimate of 98.4% or a conservative survival rate estimate of 92.3% (based on the Kaplan–Meier survival curve from a previous study) and the US Census 2020 estimate of 329,992,681 on prevalence day. 

Conclusions: This study suggests that the prevalence of FOP is higher than the often-cited value of 0.5 per million. Even so, because inclusion in this study was contingent upon treatment by the authors, IFOPA membership with confirmed clinical diagnosis, and the FOP Registry, the prevalence of FOP in the US may be higher than that identified here. Thus, it is imperative that efforts be made to identify and provide expert care for patients with this ultra-rare, significantly debilitating disease.

Pignolo, R. et al. (2021). Prevalence of fibrodysplasia ossificans progressiva (FOP) in the United States: estimate from three treatment centers and a patient organization. Orphanet Journal of Rare Diseases 16:350.

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