Healthcare Transition Preparation in X-Linked Hypophosphatemia
Authors: Dahir Kathryn , Dhaliwal Ruban , Simmons Jill H , Imel Erik A , Gottesman Gary S , Mahan John D , Prakasam Gnanagurudasan , Hoch Allison I , Ramesan Prameela , de Ferris Maria Díaz-González 
Published: May 2021

Abstract
Introduction/Background: X-linked-dominant hypophosphatemia (XLH), formally known as vitamin-D-resistant rickets, is a rare, hereditary, chronic and progressive skeletal disorder, often perceived as a childhood disease only. Its estimated prevalence is 1 in 20,000. The perception that XLH does not require treatment once the growth plates fuse means that many adolescents/young adults (AYA) are lost to follow-up and then seek care for chronic musculoskeletal symptoms, including the consequences of osteomalacia (bone pain, pseudofractures, fractures) during adulthood. There is a need to improve the healthcare transition (HCT) preparation for AYA with XLH and other rare metabolic bone disorders (MBD) to facilitate consistent and effective care throughout the life span and lessen the psychosocial and economic burden associated with these disorders.
Methods/Statement of the Problem: HCT timelines, milestones, and educational tools exist for some chronic conditions such as diabetes or kidney disease, but these programs do not meet the unique needs and nuances of patients with XLH and other rare MBD as they transfer to adult-focused healthcare. Consequently, specific tools and resources tailored by disease experts for these AYA are needed.
Results/Proposed Solution: Detailed timelines with milestones and a description of a HCT program for AYA with XLH and other rare MBD have been adapted from best practice protocols. This program reflects the specific needs of, and complexities associated with these conditions. Furthermore, this approach describes how to facilitate better communication between adult- and pediatric-focused providers and their interdisciplinary teams. Our approach is guided by patient/caregiver input and existing models for research/clinical care, with the use of validated tools to measure HCT readiness. We identified the need for psychosocial and access-related resources for AYA emancipation from parental involvement, including a guidance document for parents on how to empower their child to take ownership of the disease as they grow. In addition, it is helpful to provide disease education, genetic counselling and guidance on family planning, to encourage patients to advocate for their healthcare (as access to specialists may be limited by geographical location), and to facilitate communication/education to patients through channels familiar to and accepted by AYA (e.g. online portals, text messages). Clear HCT preparation guidelines and treatment-related goals are defined for all stakeholders. A portfolio of supporting materials underpins optimization of outcomes as AYA with XLH and rare MBD transfer from pediatric- to adult-focused healthcare.
Conclusion: Development of HCT tools/resources specific to XLH and other rare MBDs can help prevent loss to follow-up and promote continuous clinical care, thus driving better outcomes for AYA with these conditions.