X-linked hypophosphatemia: 2026 so far

More real-world follow-up connected phosphate gains to symptoms.

New 2026 reports added longer and more comparative routine-care evidence. In one adjusted analysis, adults on burosumab were reported to have higher phosphate and better pain, stiffness, and function scores than adults on oral phosphate plus active vitamin D. Multiple cohorts also continued to show phosphate increases after starting burosumab. Pediatric studies continued to report improved phosphate handling and better rickets severity on x-rays over about a year, with a walking-test improvement in a subgroup. Across these datasets, lab and imaging improvements were more consistent than changes in some day-to-day measures (for example, fatigue or mobility in one program, and links with height, quality of life (QoL; how health affects daily living), or motor function in one 1-year pediatric analysis). This means different outcomes did not always move together, so the most reliable changes in these reports were in phosphate-related labs and rickets imaging, while symptom and function changes varied by study and measure.

Research covered in: January 2026, March 2026, April 2026, July 2026, September 2026

Reports clarified pain patterns and persistent adult burden.

In the months covered, several reports emphasized that pain and daily-life impact remain major parts of XLH, especially in adults, even when lab measures improve with treatment. Registry and cohort data added detail that pain is common and can include neuropathic-like pain (pain that feels nerve-related) or unclear patterns. These patterns were linked with worse sleep and mental health symptoms. Adult registries also documented quality-of-life scores below population norms, along with frequent skeletal and dental problems. In claims-based analyses, prescription pain-medication use was common before burosumab and often changed little after starting it, with only a modest change reported in children in a second year. This suggests that prescription-based pain measures may not shift quickly, so pain and quality-of-life burden can remain substantial and may not be reflected by prescription changes or by lab improvements in these reports.

Research covered in: January 2026, April 2026, July 2026

Short-term markers aligned; longer-term PTH questions surfaced.

Several 2026 reports helped clarify which monitoring signals may be most informative during treatment. In one pediatric dataset, changes in alkaline phosphatase (ALP; a blood marker related to bone activity) closely tracked changes in rickets severity on x-rays over one year. In that same analysis, the ALP changes did not clearly line up with changes in height, quality of life, or motor function. A different monitoring question came from longer follow-up in a separate pediatric cohort: PTH increased over three years on burosumab, and a minority developed secondary hyperparathyroidism (overactivity of the parathyroid glands due to another problem). In contrast, a shorter pediatric study reported stable PTH on average. Taken together, these reports suggest ALP may mirror bone-imaging changes over months, while PTH trends may only show up with longer follow-up and still had uncertain clinical meaning in the available data.

Research covered in: March 2026, July 2026, September 2026

Reports showed missed variants and uneven testing availability.

In the months covered, case reports and meeting summaries added detail on how XLH is confirmed and why diagnosis can be delayed. Several hard-to-detect PHEX changes were described. These included a partial LINE-1 insertion found in a child and also in his mother, and a deep intronic PHEX variant (a change in a non-coding region that can disrupt splicing) identified through whole-genome plus RNA testing (testing DNA and RNA to find changes standard tests can miss) after standard testing was negative. Another report described an intronic PHEX variant missed on clinical exome but found on a targeted panel, with a possible mosaic pattern. Separately, a regional clinician meeting summary described delays linked to limited access to genetic testing and FGF23 testing (a hormone test linked to phosphate control) and differences in reimbursement. One child case also noted that burosumab was considered but not accessible in Morocco. In practical terms, these reports show that getting a clear genetic answer may depend on using the right testing approach and on local access, which can affect documentation and treatment planning.

Research covered in: May 2026, June 2026, July 2026, September 2026

Reports clarified tooth-structure changes that may help explain dental problems, alongside mixed bone-scan signals.

So far in 2026, several reports made the dental and skeletal complication profile more specific. They also showed that common tests can be difficult to interpret in XLH. Dental studies and reviews emphasized that infections and tooth loss can relate to internal tooth structure problems in dentin and pulp (the inner tooth layers), including enlarged pulp spaces and dentin defects described in small patient reports. Translational work on conventional therapy also suggested persistent or only partly corrected dental tissue changes. For bone testing, a small cross-sectional study in treated XLH reported that spine and forearm bone density results could point in opposite directions. High-detail peripheral scans suggested weaker-looking inner bone structure at sites like the distal tibia. Overall, these reports connect dental problems to structural tooth changes (not only cavities) and show that bone test results may vary a lot depending on where and how the measurement is taken in the available small studies.

Research covered in: January 2026, March 2026, April 2026, July 2026, August 2026