Vitamin D Levels and Skeletal Quality of Life in Adult Langerhans Cell Histiocytosis.

OBJECTIVE: To prospectively evaluate the association between vitamin D optimization and quality of life (QoL) and bone metabolism in adult patients with Langerhans cell histiocytosis (LCH). DESIGN: and Methods: In this prospective, uncontrolled, observational study, 45 adult LCH patients received individualized cholecalciferol supplementation for 3 months to achieve serum 25-hydroxyvitamin D (25(OH)D) levels ≥30 ng/mL. Skeletal-related and general QoL were assessed using the QUALEFFO-41 and SF-36 questionnaires, respectively. Biochemical markers of calcium metabolism and bone turnover were measured at baseline and follow-up. Correlation and exploratory linear regression analyses evaluated associations between changes in parameters. RESULTS: 25(OH)D levels increased significantly (22.8 ± 10.3 to 34.3 ± 8.2 ng/mL, p < 0.0005), followed by a reduction in parathyroid hormone (PTH) (55.7 ± 21.1 to 49.0 ± 15.8 pg/mL, p = 0.024). Improvements were observed in QUALEFFO-41 subdomains (household activities, mental condition) and SF-36 domains (bodily pain, emotional role limitations). C-terminal telopeptide (CTX) levels decreased (p = 0.006), consistent with reduced bone resorption. Changes in 25(OH)D were inversely correlated with changes in PTH (r = -0.35, p = 0.024), and changes in PTH were correlated with changes in CTX (r = -0.41, p = 0.007). No correlation was found between changes in 25(OH)D and CTX. CONCLUSIONS: In this uncontrolled cohort, vitamin D optimization was associated with improvements in selected QoL domains and favourable changes in calcium metabolism and bone resorption markers, supporting routine assessment and correction of vitamin D deficiency in this population.