Adults With XLH Would Benefit From More Comprehensive Care, Study Says

Adults with X-linked hypophosphatemia (XLH) would benefit from treatment programs that include primary care physicians, physical and occupational therapists, and social workers, according to a recent report.

The study, “Osteoarthritis, Osteophytes and Enthesophytes Affect Biomechanical Function in Adults with X-linked Hypophosphatemia,” was published in The Journal of Clinical Endocrinology & Metabolism.

XLH is characterized by bone abnormalities, such as osteoarthritis and bone spurs, but the precise ways in which these complications affect physical abilities important for daily life have not been evaluated.

In the study, researchers in the U.S. evaluated nine adults with XLH, all under age 60, who had self-reported musculoskeletal disabilities but were able to walk independently.

The team compared XLH patients and healthy controls based on the results of a combination of questionnaires, full body X-rays, range-of-motion measurements in the joints, general performance tests, and gait analysis.

All patients had bony growths called enthesophytes, degenerative arthritis, and bone spurs at the spine and synovial joints, such as the hip, elbows, and knees. Enthesophytes were particularly common near the shoulders, elbows, knees, ankles, and tendon and ligament insertion sites of the pelvis.

Degenerative osteoarthritis and bone spurs were seen throughout the body, at all joints in the arms, in the pelvic girdle, and in the knees of the patients. In their hands, osteoarthritis and bone spurs were most severe at the trapeziometacarpal joint, where the wrist meets the thumb.

The researchers found that the patients had decreased range of motion at the cervical spine, hip, knee, and ankle compared to the controls.

In particular, XLH patients showed significantly lower range of motion in their cervical spine extension, hip flexion, hip extension, knee flexion, and ankle dorsiflexion — the ability to bend the toes towards the shins.

XLH patients and the controls showed similar degrees of muscle strength, but the tests used were not meant to assess muscle fatigue, which may occur faster in those with XLH, the researchers noted.

The findings also revealed that participants with XLH had greater step width, were more prone to swaying, and showed physical restriction or rigidity at the hips, knees, and ankles, compared with the controls.

Despite the small number of participants, these results support self-reported physical assessments from XLH patients in a previous study.

Pain and limited range of motion in patients restrict their ability to perform a wide variety of daily tasks, thereby lowering their overall quality of life. Especially in aging patients, these symptoms also compromise their ability to prevent a fall, a common occurrence in XLH patients.

“[A]dults with XLH would benefit greatly from an environmental assessment and identification of fall risks in the home, social, and work environments,” the team wrote.

Patients “would benefit from consultation with an occupational therapist, who can assess the work and home environment and advise on the use of adaptive equipment and treatment goals,” the scientists added.

Despite the development of therapies such as Crysvita (burosumab, by Ultragenyx Pharmaceutical and Kyowa Kirin), the findings altogether suggest that XLH patients would benefit most from a combination of primary medical care, physical and occupational therapy, and assistance from social workers.

“In conclusion, these recommendations expand upon current guidelines established for children and adolescents with XLH to include essential care for the adult population,” the scientists wrote.

A limitation of the study was that treatment history was not assessed. However, the researchers said that their “consistent radiographical and functional findings in this study supports the belief that conventional therapies and/or frequency would have had little impact [on the results].”