Burden of Disease and Functional Impairment in XLH (IdeFIX)

Identification of Longitudinal Burden of Disease and Functional Impairment in X-Linked Hypophosphatemia

Observational study comprising prospective follow up as well as retrospective chart review in order to evaluate the longitudinal course of the disease in XLH patients with a specific focus on functional impairment, physical performance and complications associated with the disease or respective treatment.

Study Overview

• Status: Active, not recruiting
• Conditions: X Linked Hypophosphatemia
• Intervention / Treatment: Other: no intervention

Detailed Description

This is an observational / non-interventional study in order to assess the longitudinal course of XLH including disease related burden of disease and functional impairment. This is accomplished by both prospective follow up of affected patients as well as retrospective chart review. Evaluation conducted as per clincal routine and specifically evaluated as part of this study will include

• baseline documententation / demographic (as obtained from medical records)
• general data on XLH-disease specific medical history
• physical examination results
• functional assessments
• technical assessments
• quality of life / questionnaires
• laboratory evaluations

• Study Type: Observational
• Enrollment (Estimated): 60

Contacts and Locations

Study Locations

• Germany
  • Wuerzburg, Germany, 97074
    • Orthopedic Center for Musculoskeletal Research, Orthopedic Department, University of Wuerzburg

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: N/A

• Sampling Method: Non-Probability Sample

Study Population

Adult patients with X-linked Hypophosphatemia

Description

Inclusion Criteria:

• Male or female, aged ≥ 18 years, inclusive, at the time of enrollment

• Diagnosis of X-linked Hypophosphatemia confirmed by

  • documented PHEX mutation in either the patient, or in a directly related family member
  • positive family history of XLH and symptoms of the disease or
  • Phosphaturia + elevated serum levels of c-term FGF23 or iFGF23 and symptoms of the disease
• Written informed consent

Exclusion Criteria:

- Suspected of confirmed diagnosis of another phosphate wasting disorder

Study Plan

How is the study designed?

Design Details

• Observational Models: Cohort
• Time Perspectives: Other

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Course of disease	To document and assess the natural course of disease, associated symptoms and functional impairment in adult patients with XLH.	retrospective and up to 48 months from enrollment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comorbidities and medical treatment	Assess and document comorbidities and medical treatment regimens applied in adult patients with XLH	retrospective and up to 48 months from enrollment
Functional deficits and mobility constraints	Assess and document functional deficits and mobility constraints in adult patients with XLH	retrospective and up to 48 months from enrollment
Laboratory values	Assess laboratory parameters over time in adults with XLH	retrospective and up to 48 months from enrollment
Organ / tissue specific health issues	Describe frequency and outcome of organ / tissue specific health issues (affecting e.g. skeleton, dental health, muscles and joints) in adults with XLH	retrospective and up to 48 months from enrollment
Safety and tolerability of treatment	Evaluate safety and tolerability of various treatment regimens commonly applied in XLH patients	retrospective and up to 48 months from enrollment
Quality of life	Assess quality of life and respective determining factors in adults patients with XLH	retrospective and up to 48 months from enrollment

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Impact of treatment on physical performance	Evaluate the impact of clinical routine treatment including both medical approaches and physical therapy on physical performance and mobility of adult patients with XLH	retrospective and up to 48 months from enrollment
Medical history	Document and assess medical history of adult patients with XLH in order to understand its predictive value on burden of disease in adulthood	retrospective and up to 48 months from enrollment

Collaborators and Investigators

• Sponsor: Wuerzburg University Hospital
• Collaborators: Kyowa Kirin, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): October 1, 2020
• Primary Completion (Actual): November 30, 2024
• Study Completion (Estimated): October 1, 2026

Study Registration Dates

• First Submitted: June 22, 2021
• First Submitted That Met QC Criteria: June 22, 2021
• First Posted (Actual): June 30, 2021

Study Record Updates

• Last Update Posted (Actual): July 20, 2025
• Last Update Submitted That Met QC Criteria: July 16, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Urogenital Diseases; Bone Diseases; Musculoskeletal Diseases; Nutrition Disorders; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Metabolism, Inborn Errors; Genetic Diseases, Inborn; Metabolic Diseases; Bone Diseases, Metabolic; Phosphorus Metabolism Disorders; Avitaminosis; Deficiency Diseases; Malnutrition; Metal Metabolism, Inborn Errors; Rickets, Hypophosphatemic; Rickets; Hypophosphatemia, Familial; Renal Tubular Transport, Inborn Errors; Calcium Metabolism Disorders; Vitamin D Deficiency; Hypophosphatemia; Familial Hypophosphatemic Rickets
• Other Study ID Numbers: IdeFIX

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data cannot be shared in order to warrant patients privacy.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No