APA Dictionary of Psychology

a disorder in which a male is born with a double complement of the normal XY chromosome pair (46, XY). Skeletal deformities, genital anomalies leading to infertility, enlarged breasts, and eunuchoid abdominal and hip fat are among the physical traits. Learning disabilities, especially reading problems, are common, along with delayed development of motor skills. Also called 48,XXYY syndrome.