Overview of patients' cohorts in the French National rare disease registry.

In France, all patients followed by Rare Disease (RD) expert centers have to be registered in the National Rare Disease Registry (BNDMR). This database collects a minimum data set including diagnosis coded using the Orphanet nomenclature. Overall, 753,660 patients were recorded from 2007 to March 2022 including 493,740 with at least one rare disease diagnosis. Among these rare disease diagnoses, 1,300 diagnoses gathered between 10 and 70 patients and 792 gathered more than 70 patients, corresponding to more than one patient per million inhabitants. A total of 47 rare disease diagnoses with point prevalence or incidence reported in the literature below 1/1,000,000 have more than 70 patients in the BNDMR, suggesting larger BNDMR cohorts than expected from reported literature. As a conclusion, our national RD registry is a great resource to facilitate patients' recruitment in clinical research and a better understanding of RD natural history and epidemiology.