Cortical bone status and its determinants in pediatric Klinefelter syndrome.

Cortical bone deficiency in adults with Klinefelter syndrome (KS) is a well-established concern. Whether this deficit originates from impaired bone accumulation during childhood or adolescence remains unclear. Thus, we aimed to assess cortical bone status in children and adolescents with KS using automated digital X-ray radiogrammetry (DXR), while examining associations with hormonal, radiographic and anthropometric factors. In a cohort of 50 paediatric patients with KS, we retrospectively collected anthropometric measurements, Bone Health Index (BHI) and bone age readings by the BoneXpert method. Digit 2 (D2) and 4 (D4) lengths and ratio were calculated. Lumbar spine bone mineral density (LS BMD) data and hormonal measurements were accessible for 30 and 22 patients, respectively. While mean bone age was not significantly advanced, the mean BHI Z-score was significantly decreased (-0.56 (0.99)). LS BMD Z-scores were normal. Half of the patients had a serum 25-hydroxyvitamin D (25-OHD) below 20 µg/L. KS males with a BHI Z-score below -1 were significantly older and had significantly lower 25-OHD levels. BHI Z-score did not correlate with serum hormones, Z-scores of bone age, LS BMD and D2:D4 ratio. Cortical bone accumulation, evaluated through DXR, is only slightly reduced in pediatric KS. Advanced age and lower circulating 25-OHD emerged as clinical risk factors for a lower BHI. BHI Z-scores were not associated with the D2:D4 ratio or LS BMD Z-scores. Therefore, BHI-Z scores are inapt to predict LS BMD Z-scores, though their potential to predict fractures warrants further study.