X-linked hypophosphatemia (XLH) is a rare, inherited disorder characterised by renal phosphate wasting, leading to hypophosphatemia and impaired bone mineralisation. While conventional therapy with oral phosphate and active vitamin D aims to mitigate these effects, many adult patients continue to exhibit signs of osteomalacia. This persistence underscores a critical unmet need in managing the long-term skeletal complications of XLH.
X-linked hypophosphatemia (XLH) is an inherited disorder caused by mutations in the PHEX gene, which leads to elevated fibroblast growth factor 23 (FGF23) levels. This excess FGF23 results in renal phosphate wasting and impaired 1,25-dihydroxyvitamin D production, culminating in chronic hypophosphatemia and defective bone mineralisation, known as osteomalacia in adults and rickets in children. The clinical manifestations of XLH in adults include bone pain, fractures, pseudofractures, osteoarthritis, and enthesopathy. Conventional treatment strategies involve oral phosphate supplementation and active vitamin D analogues (e.g., calcitriol or alfacalcidol) to correct hypophosphatemia and improve calcium and phosphate homeostasis. However, the efficacy of this conventional approach in fully resolving osteomalacia in adult patients remains a significant clinical challenge.
Understanding Persistent Osteomalacia in XLH Adults
Despite adherence to conventional therapy, a substantial number of adult patients with XLH continue to experience symptoms and radiographic evidence consistent with osteomalacia. Histological studies of bone biopsies from adult XLH patients on conventional treatment frequently reveal persistent defects in mineralisation, characterised by increased osteoid volume and thickness, and reduced mineralisation front. This indicates that while conventional therapy may improve some biochemical parameters, it often does not fully normalise bone histology or resolve the underlying osteomalacia. The persistence of osteomalacia contributes to ongoing bone pain, increased fracture risk, and reduced quality of life in these patients. The chronic nature of the disease and the limitations of conventional therapy highlight the need for more effective treatment modalities that can directly address the FGF23-mediated pathophysiology of XLH and achieve more complete resolution of bone mineralisation defects.
The continued presence of osteomalacia in adult XLH patients, even those receiving conventional phosphate and active vitamin D therapy, presents a clear challenge to current clinical practice. It suggests that simply replacing lost phosphate and vitamin D is insufficient to counteract the profound effects of elevated FGF23 on bone metabolism. Clinicians must recognise that a patient's biochemical markers may appear within an acceptable range, yet their bone health could still be compromised, leading to ongoing pain and fracture risk. This calls for a more nuanced approach to monitoring, potentially incorporating bone biopsies or advanced imaging techniques to assess the true extent of osteomalacia.
For the pharmaceutical industry, the persistent unmet need in adult XLH patients underscores the value of therapies that directly target the FGF23 pathway. Burosumab, an anti-FGF23 antibody, represents a significant advancement in this regard, offering a mechanism of action that addresses the root cause of the disease rather than merely managing its symptoms. The continued prevalence of osteomalacia in conventionally treated patients provides a strong rationale for the earlier and broader adoption of such targeted therapies, particularly in adults who have already accumulated significant skeletal damage.
Ultimately, patients with XLH deserve treatments that offer more than symptomatic relief. The goal should be to normalise bone histology and prevent the long-term complications associated with chronic osteomalacia. This requires a shift in perspective, moving beyond the traditional reliance on phosphate and active vitamin D alone, and embracing therapies that offer a more complete correction of the underlying pathophysiology. The data on persistent osteomalacia should serve as a call to action for both clinicians and industry to re-evaluate treatment paradigms and ensure that adult XLH patients receive the most effective care available.
- The Pivot Conventional therapy for XLH often fails to fully resolve osteomalacia in adults.
- The Data A significant proportion of adult XLH patients continue to show radiographic and histological evidence of osteomalacia.
- The Action Clinicians should be aware that osteomalacia may persist in adult XLH patients despite standard treatment, necessitating careful monitoring and consideration of alternative or adjunctive therapies.
ART-2026-373
Cite This Article
Team TLSFE. Xlh adults: osteomalacia persists despite conventional therapy. The Life Science Feed. Published June 14, 2026. Updated June 14, 2026. Accessed June 14, 2026. https://thelifesciencefeed.com/endocrinology/adrenal-gland-diseases/news/xlh-adults-osteomalacia-persists-despite-conventional-therapy.
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