Abstract
We report an 18-yr-old Japanese boy with a 48,XXYY karyotype and extreme tall stature (194 cm). A GnRH test at 12.5 yr of age showed hypergonadotropism (LH, 4.2→72.2 mIU/mL; FSH, 28.9→61.7 mIU/mL), and an hCG test at 15.5 yr of age revealed a normal testosterone response (1.67→4.08 ng/mL). The tall stature is remarkable, because the mean adult height of Caucasian 48,XXYY patients is 181 cm. Although the underlying factors for the tall stature are unknown, this report indicates an association of the 48,XXYY karyotype with marked tall stature.
