SUN-527 Clinical Experts' Views Regarding the Impact of X-Linked Hypophosphatemia on Health-Related Quality of Life (HRQL)

X-linked hypophosphatemia (XLH) is a rare inherited genetic and chronic, progressive disorder of renal phosphate wasting. It is the most common form of familial hypophosphatemic rickets (vitamin D-resistant rickets) [1]. XLH causes bone deformity including short stature, bowed legs, and osteomalacia. Children and adolescents with XLH can experience pain, loss of physical functioning and ability to complete normal activities, some may experience a psychological and social impact too [2]. More qualitative data on the impact of XLH on HRQL could improve our understanding of the condition. This research is specifically aimed at understanding the burden of this condition in children and adolescents, and any variation by age and severity of XLH. A literature review explored the impact of XLH on patients. Based on the limited information available, draft vignettes describing problems with mobility, pain, appearance, impact on everyday activities, dental problems and social relationships were developed by severity and age. Severity was defined by the Thacher Rickets Severity Score (RSS) (healed=0; mild=0.5-1.0; moderate 1.5-2.0; severe >2.5). Vignettes were defined by the age groups of 1-4yrs, 5-12yrs and +13yrs. The 12 vignettes were then reviewed by 6 experienced clinical experts (5 hospital-based pediatricians and 1 specialist nurse) during interviews to explore how accurately they reflected their clinical experience. The experts indicated that disease severity can be associated with greater pain and more limitations in daily activities. They provided consistent information on the loss of physical functioning, pain, impact on usual activities, and the impact of limb deformities on physical functioning. For some areas of HRQL - such as the effect of XLH on sleep, and aspects of social functioning, physicians were less able to assess the impact. Experts reported that the psychological impact is greater in older children; some also stated that very young children tend not to experience pain like older children do. These vignettes provide a useful insight of the impact of XLH on HRQL, in children and adolescents indicating a broad impact on multiple domains. More work is underway to understand from parents and young people themselves the different ways in which XLH affects their HRQL. References 1. Linglart A, Endocr Connect. 2014: 18:EC-13. 2. Forestier-Zhang L, Orphanet J Rare Dis. 2016; 11(1): 160.