Fig. 1

Waterfall of United States FOP patient population estimate on 22 July 2020. A pooled total of 720 patients were identified based on the 3 sources (the IFOPA membership list and FOP Registry were considered together as one source). Following deduplication based on first/last initial, sex, date of birth, and location, 373 unique patients were identified. Of these patients, 294 had not been reported to be deceased. Ten patients without sufficient data (year of birth, date of last contact) to calculate the survival-weighted prevalence were removed. After application of a survival prediction based on patient age at last contact and time since last contact (prevalence date of 22 July 2020), an unadjusted prevalence of 0.85 per million was calculated. After adjusting using a conservative survival rate (92.3%) based on the bottom quintile of the average estimated survival rate reported by Kaplan 2010 [2], an adjusted prevalence of 0.88 per million was calculated. When instead adjusting using the average survival rate of 98.4% reported by Kaplan 2010 [2], the adjusted prevalence is 0.88 per million