Growth Patterns and Bone Maturation in Children with Sex Chromosomal (45,X/46,XY) DSD

OBJECTIVE: To assess growth patterns and bone maturation in children with 45,X/46,XY mosaicism and to optimise final height prediction. DESIGN: Multicenter retrospective registry-based cohort study. METHODS: Ninety-five cases of 45X/46XY mosaicism from 26 centers were included. Longitudinal growth data were available for 54 participants and stratified by external genitalia score (EGS): Group 1 (EGS 0-4) and Group 2 (EGS 4.5-12). Growth was evaluated using mean height SDS based on male and female references. Bone age was reassessed centrally using the Greulich and Pyle method. Predicted adult height (PAH) and target height (TH) were compared with near-final height (nFH) using male and female standards. GH treatment outcomes were analyzed. RESULTS: Mean nFH was 157.5 cm in Group 1 and 160.3 cm in Group 2 (n.s.). Growth aligned more closely with female reference curves, with nFH at -0.7 SDS (Group 1) and -0.3 SDS (Group 2) on female charts, and -2.0 and -1.6 SDS on male charts. Bone age was delayed using female standards and advanced using male standards. Female-based PAH slightly underestimated nFH, whereas male-based PAH slightly overestimated it. PAH approximated nFH more accurately than TH. nFH was similar in those who did and did not receive GH treatment, although interpretation was limited by small sample size and treatment bias. CONCLUSION: Female growth charts and bone age readings best reflect longitudinal growth and maturation in individuals with 45,X/46,XY DSD and provide the most accurate prediction of nFH. Larger prospective studies are needed to guide evidence-based treatment decisions.