ESPE Abstracts

Background: X-linked hypophosphatemia (XLH) is a rare, progressive, genetic phosphate wasting disorder leading to rickets, lower limb deformities as well as short and disproportionate stature. The condition is inherited in the majority, however spontaneous mutations are reported in ≈30% of cases. Its rarity, coupled with its diverse clinical manifestations, may lead to delayed diagnosis and subsequently delayed treatment initiation. The objective of this analysis is to investigate if there is a delay in diagnosis for children without a family history (FH) compared to those with a FH.

Methods: The International XLH Registry (NCT03193476) is a multicentre, prospective, non-interventional study initiated in 2017, aiming to recruit 1,200 people with XLH, collecting data prospectively for a period of 10 years. All participants of all ages with a confirmed diagnosis of XLH, regardless of their treatment and management, are included in the Registry.

Results: At the database lock for the first analysis (29 March 2021), 579 participants had entered the registry before 30 November 2020, of which 360 were children. Date of diagnosis and data for FH were available for 195 of the 360 children. Of 195 children, 121 (62%) reported FH of XLH, defined as having a biological parent(s) affected, whereas 74 (38%) had no FH of XLH. Of those with a FH, the biological mother was affected in 77%, biological father affected in 22%, and both affected in 1% of cases. Children aged <18 years with no FH were significantly older at time of diagnosis (3.96 years) compared to those with a FH (1.47 years), P<0.001. Males (n=74) and females (n=121) did not differ in terms of age at diagnosis.

Conclusions: All XLH patients without a FH of XLH were diagnosed significantly later than patients with a FH. Younger patients with a FH appear to be diagnosed more quickly than older patients, suggesting increased disease awareness.