ESPN 54th Annual Meeting

ESPN 2022


 
First Interim Analysis of the International X-Linked Hypophosphataemia (XLH) Registry: Paediatric Population Baseline Characteristics
DIETER HAFFNER 1 JONATHAN LIU 2 ANGELA WILLIAMS 2 SUE WOOD 2 ELENA LEVTCHENKO 3

1- HANNOVER MEDICAL SCHOOL
2- KYOWA KIRIN INTERNATIONAL
3- UNIVERSITY OF LEUVEN
 
Introduction:

 

X-linked hypophosphataemia (XLH) is a rare, progressive, hereditary phosphate-wasting disorder characterised by excessive activity of fibroblast growth factor 23. The International XLH patient Registry was established to provide information on the natural history of XLH and impact of treatment on patient outcomes. Data are from the first interim analysis conducted on baseline data from paediatric subjects (age <18y).

 

Material and methods:

 

The XLH Registry (NCT03193476) was initiated in August 2017, aims to recruit 1,200 children and adults with XLH, and will run for 10 years. At time of analysis (Last Patient In: 30/11/2020; database lock: 29/03/2021), subjects diagnosed with XLH were enrolled from 81 hospital sites in 16 countries. Parameters collected at baseline included demographics, medical and treatment history, and clinical presentation data.

 

Results:

 

Overall, 360 children were included in this analysis; 61.7% were female. Mean (SD) age was 9.5y (±4.5). Treatment data at entry were available for 281 subjects: among those 58.7% were receiving burosumab (165/281); 40.6% conventional therapy (phosphate salts and active vitamin D) (114/281); 0.7% had no treatment reported (2/281). Among 330 paediatric subjects with reported genetic data, 72.4% had a genetic test, of whom 88.7% had a confirmed PHEX mutation. Data on XLH family history were available for 319 subjects; biological mother was affected in 164 (51.4%); biological father was affected in 49/317 (15.5%). Across all age groups males and females with XLH presented with decreased standardized height (z-score: -1.63±1.22; n=307) yet ‘normal’ standardized weight (z-score: -0.02±1.35; n=326), resulting in an elevated body mass index (z-score: 1.37±2.285; n=249) suggesting obesity.

 

Conclusions:

 

This is the largest data set of children with XLH collected to date. Short stature and obesity appear as frequent complications throughout childhood. Information collected over the 10-year Registry duration will generate real-world evidence to help inform clinical practice.

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