Klinefelter syndrome, male with more than two X chromosomes

**Definition:** A disease affecting males, caused by the presence of more than two X chromosomes in each cell. This disease is characterised by impaired sexual development, intellectual disability, distinctive facial features, skeletal abnormalities, poor coordination, and severe problems with speech. This disease may be differentiated from classic Klinefelter syndrome by increased severity of symptoms. Confirmation is through observation of more than two X chromosomes by karyotyping.