Beyond the Curve: How XLH Impacts Skeletal Maturation and Predicted Height

XLH is associated with delayed skeletal maturation in children, with a distinct sex difference: males show a larger average bone age delay than females. In a retrospective longitudinal study of 56 children, the mean bone age delay was 1.2 years in males and 0.4 years in females, and severe delays (one to two years) affected about 58% of males versus 21% of females.

Some patients in both sexes exhibited delays greater than two years, complicating growth monitoring and the timing of interventions. Bone age assessment uses hand and wrist radiographs matched to standardized development atlases to gauge growth potential and guide decisions about growth-promoting therapies and expected adult height.

Despite these maturation delays, standard height prediction models remained relatively accurate for XLH patients, with predicted adult heights generally within the typical ±2 inches seen in healthy children. When applying Bayley-Pinneau, there was a tendency to overestimate height in males; Tanner-Whitehouse tended to overestimate in females.

The findings suggest bone age delay is a systemic feature of XLH and underscore the relevance of sex-specific growth patterns for management.