Patient-friendly, non-technical summary of research papers

May 2026 Research Update

This report covers research on X-linked hypophosphatemia published in PubMed in May 2026. For other months, see all research updates.

Last update: June 5, 2026

At a glance

New PHEX variant

One case report linked XLH to a newly described PHEX gene change involving a partial LINE-1 DNA insertion.

Leg and dental findings

In the same child, the report described leg deformities and a dental abscess alongside the genetic finding.

Burosumab in another FGF-23 disorder

A separate single-patient report (not XLH) found that burosumab increased blood phosphate in McCune-Albright syndrome with FGF-23–related phosphate wasting.

Evidence limited to case reports

Overall, this month’s evidence added detail on genetics and targeted treatment effects, but it was limited to two single-patient reports.

Overview

This month, the new evidence was mostly about understanding XLH and related conditions. It came from two single-patient reports rather than larger treatment trials.

One report broadened the list of genetic changes linked to XLH. A child with XLH had a newly reported type of PHEX gene change involving a partial LINE-1 insertion. The same change was also found in his mother. The report also described everyday XLH impacts in the child, including leg deformities and a dental abscess.

The second report was not in XLH. It described an adult with McCune-Albright syndrome and fibrous dysplasia who had low phosphate driven by high FGF-23 (a hormone that can cause phosphate wasting). Burosumab, a medicine that blocks FGF-23, raised blood phosphorus after conventional phosphate therapy had not worked well. Pain and quality of life were reported to improve. One bone marker called alkaline phosphatase stayed elevated after 12 months.

A kidney stone was also noted in that adult. The report linked it to earlier high-dose conventional therapy rather than clearly to burosumab.

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Research topics this month

This month did not add new results from larger XLH treatment trials, but it did add 2 detailed single-patient reports that widen the real-world picture of phosphate-wasting disorders. One report expands the known genetic changes that can cause XLH, while the other describes how blocking FGF-23 with burosumab affected an adult with a different FGF-23-driven bone condition. Together, they underline that "low phosphate" can have different causes, and that both genetics and targeted medicines are being used to understand and manage these conditions.

In a 2-year-old boy with XLH, researchers identified a previously unreported partial LINE-1 insertion in exon 22 of the PHEX gene, confirmed with follow-up testing and also found in his mother. The report adds a new type of DNA change to the list of PHEX variants that can disrupt phosphate regulation and lead to XLH, which matters because some variants may be missed without broader genetic testing approaches. The child had typical XLH-related features described in the report, including leg deformities and dental problems, which helps connect the genetic finding to everyday impacts.

In an adult woman with McCune-Albright syndrome and extensive fibrous dysplasia, burosumab (a medicine that blocks FGF-23) was used after conventional phosphate therapy did not correct the low phosphate. Her blood phosphorus normalized quickly and she reported less pain and better quality of life and strength, but one bone turnover marker (alkaline phosphatase) stayed high after 12 months. Because this is a single off-label case in a different condition than XLH, it mainly shows what is possible in one person rather than what to expect for most patients with XLH.

For families living with XLH, this month mainly adds understanding rather than changing anything in routine care. The genetic case report shows that rare, unusual DNA insertions can cause XLH, which may be important when a diagnosis is suspected but standard genetic tests do not find a clear PHEX change, although this report does not prove which test strategy is best. The burosumab case is not an XLH patient, but it reinforces the basic idea that high FGF-23 can drive phosphate wasting and that blocking FGF-23 can raise blood phosphorus in at least some settings; what remains uncertain is how broadly this applies outside approved uses and what the best long-term targets and monitoring should be in complex bone diseases.

Limitations

The evidence this month came from two single-patient reports, so it cannot show what is typical.
The burosumab report was in McCune-Albright syndrome with fibrous dysplasia, not in XLH.
Some findings were unclear for long-term tracking, such as alkaline phosphatase staying high after 12 months.

Important information

This document summarizes recent research from PubMed-indexed publications using automated methods.
It is intended for educational purposes and does not replace medical advice.
Links to the original studies are provided via PubMed, where readers can explore abstracts and, when available, access full-text articles.
Some studies may include additional details that were not accessible for this summary.
Readers seeking more complete detail or context may find it helpful to review the original studies directly.