47, XYY syndrome is a sex chromosome aneuploidy where males receive an additional Y chromosome, and is characterized clinically by tall stature evident from childhood, macrocephaly, facial features (mild hypertelorism, low set ears, a mildly flat malar region), speech delay and an increased risk for social and emotional difficulties, attention deficit hyperactive disorder and autistic spectrum disorder. The disease is 47,XYY syndrome (MONDO_0019339). Also known as: 47,XYY, Double Y, Double Y syndrome, XYY Syndrome, XYY karyotype, XYY syndrome, Y disomy, disomy Y.