Small Head Circumference and Height above Target Height as Potential Early Clues for Klinefelter Syndrome: A Retrospective Cohort Study

Background: Klinefelter syndrome (KS) is often underdiagnosed in childhood due to subtle phenotypic features.Aim: This study aimed to evaluate body measurements and proportions in patients with KS and explore the diagnostic value of auxological findings in early-lifeMethods: This retrospective observational cohort study included 16 patients with KS confirmed by lymphocyte karyotyping. Anthropometric measurements were performed by a single observer using standardized methods. Standard deviation scores (SDS) for height, weight, body mass index (BMI), head circumference (HC), sitting height (SH), and sitting height/height ratio (SHR) were calculated using national reference data. The leg proportions were evaluated using the Manouvrier’s skelic index.Results: At presentation, all patients were prepubertal. The median age was 4.3 (0.1 to 12.7) years and the median SDS values for height, weight, BMI, and HC were −0.3, −0.8, −0.5, and −1.3, respectively. Tall stature was observed in 19% of patients and small HC in 25%. SH was normal, but SHR was low. At the final evaluation, the median age was 12 years (5.2–20.3), and the height was 0.6 SDS (1.6 to 2.0); 6% had a tall stature. The SHR improved, the arm span–height difference was normal, and the final height–target height difference was 1.6 SDS (1.1 to 3.1). Small HC persisted in 25%. Long legs were present in 37.5%.Conclusion: Although the height SDS was normal, the difference from the target height was significant. Small HC—a feature not previously reported in KS—was also frequent. In children taller than the target height with long legs and small HC, KS should be considered.