Symptoms and Treatment Burden of XLH Changes Throughout Life, Study Reports

The burden of X-linked hypophosphatemia (XLH) is centered on treatment in childhood, expands to psychological impact and other factors in adolescence, and shifts in adulthood to the need for other interventions and mobility, a study reports.

These findings, which were based on responses primarily from patients and caregivers in the United Kingdom, highlight the changing nature of the symptoms and treatment burden of XLH over time. The researchers said these findings may guide the development of specific treatments and services to support patients in the three age groups.

The study, “Exploring the Burden of X-Linked Hypophosphataemia: An Opportunistic Qualitative Study of Patient Statements Generated During a Technology Appraisal,” was published in the journal Advances in Therapy.

Besides hypophosphatemia — low levels of phosphorus in the blood — people with XLH may experience symptoms such as rickets (soft and weak bones), deformities associated with abnormal bone development, delayed growth, bone-related pain, and dental problems.

“The clinical manifestations and symptoms of XLH can have a substantial impact on physical function, mobility and overall quality of life,” the researchers said.

The complexity and rarity of XLH have represented challenges to assessing its impact over a lifetime, especially from a patient perspective.

A team of researchers in the U.K. assessed the real-world symptoms and treatment burden of XLH in children, adolescents, and adults through the views of patients and caregivers, as reported during a National Institute for Health and Care Excellence (NICE) online open consultation.

This consultation, which occurred from June to July 2018, was primarily designed to assess the therapeutic impact of Crysvita (burosumab) in these patients, with the aim of informing reimbursement decisions in England. Crysvita was developed and marketed by Ultragenyx Pharmaceutical and Kyowa Kirin.

However, since the consultation included questions on the disease’s symptom and treatment burden, the findings it generated helped inform patient and caregiver perspectives of XLH’s impact.

Responses from 95 patients — 32 children, 18 adolescents, and 45 adults — were included in the analysis. About 73% of adult responses were submitted by the patients themselves, while 81% of the responses of children and 72% of those of adolescents were submitted by their parents.

Most responses were given by U.K.-based patients (77%), with 9% reported from the U.S. participants, and 1% from Australia.

To analyze the data, researchers and clinicians generated 81 codes based on the expected aspects of XLH burden. Based on the collected answers, 15 more codes were introduced. Most were related to less common symptoms, such as muscle pain or numbness, movement, psychological aspects, relationships, healthcare, and employment.

The results showed that the most frequently reported burdens were associated with treatment, psychological aspects, movement, healthcare, rickets, and other symptoms.

In children, the greatest XLH burden was related to treatment, with dosing regimens and pain being the most frequently reported causes of burden. Treatment side effects, including diarrhea and abdominal pain, also were reported to affect patients’ quality of life.

During adolescence, the burden became increasingly complex, expanding to other factors. This also was the time when the disease induced a greater impact on the patients’ psychological health, with frequent reports of low self-esteem, lack of self-confidence, and bullying. The burden of orthopedic surgery to correct bone deformities also was evident at this phase.

As in children and adolescents, conventional therapy was a major factor related to XLH burden in adults, being associated with bone deformity and orthopedic surgery. Pain, mobility, treatment, fatigue, and dental problems also were frequently reported as contributors to disease burden among adults. Reports of impacted quality of life also were common.

“We show that there is a clear evolution of the burden of XLH from being treatment-centric in childhood to multi-factorial in adolescents with a rise in psychological burden and high impact on need for other interventions, function and mobility in adulthood,” the researchers said.

Future studies are required to fully understand the disease burden throughout life. However, the investigators said this type of study “offers a valuable opportunity to improve awareness of the burden of disease to aid healthcare professionals in their treatment considerations.”

“This evidence can provide a different perspective to address uncertainties seen in the evidence presented, along with enabling a decision-making body to better understand any risks that patients are willing to take in order to access a new therapy,” the researchers said.