Determinants of final height in X-linked hypophosphatemia: impact of diagnostic delay and baseline growth in a Brazilian cohort.

Background: X-linked hypophosphatemia (XLH) is a rare genetic disorder characterized by impaired phosphate metabolism, leading to rickets and growth failure. Delayed diagnosis may worsen growth outcomes, particularly in settings with limited access to specialized care. This study evaluated determinants of final height in a Brazilian cohort, focusing on age at diagnosis and baseline growth status. Methods: This retrospective observational cohort study included 41 patients with molecularly confirmed XLH followed at a tertiary referral center in Brazil between 1971 and 2025. Anthropometric and clinical data were extracted from medical records. Final height analysis was restricted to 20 patients treated exclusively with conventional therapy. Correlations were assessed using Spearman coefficients, and multivariable linear regression was performed to identify independent predictors of final height Z score. Results: At diagnosis, the mean height-for-age Z-score was -1.90 ± 1.56, indicating significant baseline growth impairment. Age at diagnosis was inversely correlated with height-for-age Z-score ( Conclusions: Final height in XLH is influenced by a combination of genetic potential, baseline growth impairment, and timing of diagnosis. Delayed diagnosis is associated with greater growth deficits and suboptimal adult height, even under conventional therapy. These findings highlight the importance of early recognition and provide a benchmark for evaluating growth outcomes in the era of targeted therapies.