Twenty years of the Fabry Outcome Survey (FOS) : insights, achievements, and lessons learned from a global patient registry

Background: Patient registries provide long-term, real-world evidence that aids the understanding of the natural history and progression of disease, and the efects of treatment on large patient populations with rare diseases. The year 2021 marks the 20th anniversary of the Fabry Outcome Survey (FOS), an international, multicenter, observational registry (NCT03289065). The primary aims of FOS are to broaden the understanding of Fabry disease (FD), an X-linked lysosomal storage disorder, and to improve the clinical management of afected patients. Here, we review the history of FOS and the analyses and publications disseminated from the registry, and we discuss the contributions FOS stud‑ ies have made in understanding FD. Results: FOS was initiated in April 2001 and, as of January 2021, 4484 patients with a confrmed diagnosis and patient informed consent have been enrolled from 144 centers across 26 countries. Data from FOS have been pub‑ lished in nearly 60 manuscripts on a wide variety of topics relevant to FD. Analyses of FOS data have investigated the long-term efectiveness and safety of enzyme replacement therapy (ERT) with agalsidase alfa and its efects on morbidity and mortality, as well as the benefts of prompt and early treatment with agalsidase alfa on the progression of cardiomyopathy and the decline in renal function associated with FD. Based on analyses of FOS data, ERT with agal‑ sidase alfa has also been shown to improve additional signs and symptoms of FD experienced by patients. FOS data analyses have provided a better understanding of the natural history of FD and the specifc populations of women, children, and the elderly, and have provided practical tools for the study of FD. FOS has also provided methodology and criteria for assessing disease severity which contributed to the continuous development of medical practice in FD and has largely improved our understanding of the challenges and needs of long-term data collection in rare diseases, aiding in future rare disease real-world evidence studies. Conclusion: FOS over the last 20 years has substantially increased the scientifc knowledge around improved patient management of FD and continues to expand our understanding of this rare disease