Endocrine Abstracts

Background: X-Linked Hypophosphataemia (XLH) is a rare, progressive, hereditary phosphate wasting disorder characterised by a pathological increase in fibroblast growth factor 23 concentration/activity. Despite XLH being increasingly recognised as a chronic progressive disease, there are few data documenting its natural history or impact of treatment. The International XLH Registry will collect data to characterise burden of disease, disease progression and long-term outcomes. It aims to describe effectiveness and safety of treatments used to manage XLH and their value in certain subpopulations.

Methods: The International XLH Registry (NCT03193476) was initiated August 2017, aims to recruit 1,200 children and adults with XLH, and will run for 10 years. This is a multicentre, non-interventional registry, capturing treatment details and clinical outcomes in patients with XLH who are followed for as long as informed consent/assent and regulatory permissions are maintained. Only data collected during standard routine examinations are recorded, no specific examinations/data entries are mandated. Parameters collected at baseline included demographics, medical history, treatment history, and clinical presentation data. The conduct of the International XLH Registry is overseen by 17 Steering Committee expert physicians representing the region.

Results: As of 31 December 2021, 1,043 subjects diagnosed with XLH were enrolled from 88 hospital sites in 19 countries. The geographic distribution of subjects is as follows: Belgium n=29, Bulgaria n=7, Czech Republic n=8, Denmark n=23, France n=267, Germany n=79, Hungary n=11, Ireland n=5, Israel n=21, Italy n=88, The Netherlands n=26, Norway n=23, Portugal n=9, Slovakia n=5, Slovenia n=3, Spain n=55, Sweden n=43, Switzerland n=17, and the UK n=324. A further 30 sites are still to enrol patients (including in Austria and Latvia). Overall, 400 adults (18–29y, n=116; 30–39y, n=81; 40–49y, n=95; 50–59y, n=58; ≥60y, n=50) and 620 paediatric subjects (<5y, n=138; 5–12y, n=321; 13–17y, n=161) have been enrolled (date of birth unavailable, n=23). The majority of the enrolled subjects are female (648 (62.1%)), with 372 male (35.7%) and 23 for whom sex was not reported (2.2%).

Conclusions: This Registry forms the largest dataset of XLH subjects worldwide to date. Patients have been recruited from a wide geographical region, and baseline demographics are consistent with a hereditary X-linked dominant disease. Information collected during the 10-year Registry duration will generate real-world evidence to help inform clinical practice throughout the EMEA region and beyond.

Acknowledgements: Authors acknowledge the contribution of all members of the International XLH Registry Steering Committee.