January 2026 Research Update

Studies this month add a clearer picture that burosumab can move the main XLH lab problem (low phosphate) in the right direction, and that some people also report feeling and functioning better. The adult study showed improvements over 48 weeks, while the infant series showed early treatment was feasible with improved phosphate but not full normalization and with varied growth. Together, these studies suggest benefits may show up in both lab results and daily-life measures, but individual responses can differ. [1] [2]

In a small group of 18 Chinese adults, burosumab increased average fasting blood phosphate from 1.6 to 2.4 mg/dL and improved kidney handling of phosphate, which is the intended biological effect. People also reported less pain and stiffness and better physical function, and their 6-minute walk distance increased by about 52 meters. Side effects were mostly mild to moderate, and the study reported no serious treatment-related safety signals. [1]

In three infants who started burosumab before 12 months of age and were followed for at least a year, phosphate levels improved but did not fully normalize. Two infants had satisfactory linear growth and favorable bone x-ray findings, while one had growth faltering that the authors thought might relate to sleep-disordered breathing or phosphate imbalance. No significant adverse effects were reported in this small series, but dosing was individualized and higher than guidelines. [2]

For patients and caregivers, this month mainly strengthens the practical understanding of what burosumab can change in the body and what people may notice day to day. The adult data may matter now because it reflects real outcomes over about 1 year, but it is still a small, single-arm study without a comparison group. The infant report is early evidence that treatment can be started very young with generally reassuring short-term observations, while also highlighting that growth and phosphate responses may not look the same for every child. What remains uncertain is how these results compare to other care approaches and how well they predict longer-term outcomes. [1] [2]

This month adds detail about how pain is experienced in XLH, including the idea that not all pain fits a simple "injury or inflammation" pattern. In an online registry, pain was common and sometimes widespread, and certain pain patterns were linked to worse sleep and mental health symptoms. This helps explain why pain in XLH can feel complex and why different people may describe very different pain experiences. [3]

Across adults with XLH and two other rare bone conditions, 86% reported current pain and 18% reported more widespread pain across the body. Using a questionnaire that groups pain into patterns, most people had nociceptive-type pain, but 14% had neuropathic-like pain and 22% had an unclear pattern; these two groups reported a higher overall burden of pain. Anxiety, depression, and poor sleep were more common with widespread pain and with neuropathic-like pain, while the unclear pain pattern was linked to depression and poor sleep. [3]

For patients, this study mainly adds language and structure for describing pain, including that some pain can have nerve-like features or mixed features rather than a single clear cause. It may matter now for understanding symptoms because it connects certain pain experiences with sleep and mental health difficulties, which can shape daily life. Because the data were self-reported and measured at one point in time, it cannot show what causes what or how pain changes with treatment. It still helps clarify that tracking pain quality (not just intensity) may be important in research and in conversations about lived experience. [3]

This month included an individual report that shifts attention to how XLH can show up outside the skeleton, especially in the teeth. In this child, unusual dental findings led to XLH being recognized earlier than typical bone symptoms. The report highlights that treatment may involve both dental procedures and systemic XLH therapy working in parallel. [4]

In a 4-year-old boy, dental x-rays showed tooth and root problems that prompted genetic testing and an XLH diagnosis. After dental treatments (including root canal-type treatment and one extraction) and starting burosumab, the report described improved phosphate-related lab measures and stability of most treated teeth at 12 months. The child continued with ongoing follow-up across dental and medical specialties. [4]

For families, this case mainly matters as an example that dental issues can sometimes be an early clue of XLH, even before obvious bone symptoms. It does not prove what will happen for other children, but it illustrates the kinds of dental problems that can occur and the need for coordination across dental and medical care in some situations. The evidence here is very early because it is one patient, and details like longer-term dental outcomes were not available. It still helps clarify that XLH can involve teeth in ways that may require active monitoring in research and care pathways. [4]