XYY Syndrome

XYY syndrome, also called 47,XYY or Jacob's syndrome, is an intersex trait affecting approximately 1 in 1000 people assigned male at birth. It is a chromosomal condition causing one to have an extra Y chromosome (XYY), instead of the typical one (XY). Symptoms may include delayed development of language and/or motor skills, involuntary tremors or tics, and increased likelihood of seizures, asthma, and learning disabilities. Physical features caused by this condition can include increased height, a large head, flat feet, and widely spaced eyes. Since this condition does not always cause obvious or unusual symptoms, some may go most or all of their lives without knowing they are affected.