Comparison of adolescents with Klinefelter syndrome according to the circumstances of diagnosis: amniocentesis versus clinical signs.

Aims: We compared the phenotype of adolescents with Klinefelter syndrome diagnosed by amniocentesis or postnatally to the general population with a view to evidence-based genetic counselling.

Methods: The charts of 28 patients seen between ages 12 and 18 years were reviewed. Physical and neurodevelopmental data were compared between patients diagnosed by chance (amniocentesis, group A, n = 11) or on the basis of symptoms (group B, n = 17) and the general population. Our hypothesis was that group A would have a more heterogeneous and less severe phenotype than group B.

Results: All patients had spontaneous puberty. The 2 patient groups were similar in physical development. Mean testosteronemia became lower than the normal mean from age 14 years. Compared to the general population, the prevalence of gynecomastia and school delay in group A was not significantly different (gynecomastia 33 vs. 40%, p = 0.70; school delay 40 vs. 20%, p = 0.25). In contrast, gynecomastia (77%) and school delay (56%) were significantly more frequent in group B than in the general population (p = 0.01 for both).

Conclusions: Although they are based on a small number of patients, our data provide the groundwork for cautious optimism in prenatal counselling for Klinefelter syndrome.