Prevalence of Comorbid Hyperparathyroidism and Its Association with Renal Dysfunction in Asian Patients with X-Linked Hypophosphatemic Rickets/Osteomalacia

In patients with X-linked hypophosphatemic rickets/osteomalacia (XLH) in Asia, the current prevalence of hyperparathyroidism and its association with renal dysfunction have not been determined. We used patient data retrospectively collected up to the time of informed consent in the SUNFLOWER study, a long-term observational study, to investigate the current treatment status and prevalence of comorbid hyperparathyroidism and its association with renal dysfunction in patients with XLH in Japan and South Korea. Of 69 patients who met the eligibility criteria, 32 (46.4%) did not have hyperparathyroidism (hereinafter referred to as non-hyperparathyroidism), 33 (47.8%) had secondary hyperparathyroidism, and four (5.8%) had tertiary hyperparathyroidism. Men were more prone to develop secondary and tertiary hyperparathyroidism, use oral phosphate at higher frequencies, and have a higher incidence of Stage ≥ 3 chronic kidney disease and Grade ≥ 3 renal calcification than women. Ongoing treatments for patients with XLH and non-hyperparathyroidism, secondary hyperparathyroidism, and tertiary hyperparathyroidism mainly consisted of active vitamin D (30 [93.8%], 25 [75.8%], and 3 [75.0%], respectively) and oral phosphate (21 [65.6%], 23 [69.7%], and 4 [100.0%], respectively). At informed consent, patients with tertiary hyperparathyroidism had the lowest estimated glomerular filtration rate values. Our study highlights the prevalence of comorbid hyperparathyroidism and its association with renal dysfunction in patients with XLH through a large-scale observational study in Asia.Trial registration: NCT03745521; UMIN000031605.