XYY syndrome

Also known as Y disomy, Disomy Y, 47,XYY, Double Y, XYY Karyotype, 47,XYY Syndrome, Double Y syndrome

genetic condition in which a male has an extra Y chromosome

Key facts

Other names: 47,XYY
Specialty: Medical genetics
Symptoms: None, being taller than the parents, mildly unusual physical features, severe acne , poor coordination , weak muscle tone , learning and speech problems
Usual onset: At conception
Duration: Lifelong
Causes: Two Y chromosomes in males
Diagnostic method: Genetic testing
Differential diagnosis: Klinefelter syndrome , Marfan syndrome , Sotos syndrome
Prevention: None
Treatment: Speech therapy , tutoring
Prognosis: Normal life expectancy
Frequency: ~1 in 1,000 males

Article

XYY syndrome, also known as Jacobs syndrome and Superman syndrome, is an aneuploid genetic condition in which a male has an extra Y chromosome. There are usually few symptoms. These may include being taller than average and an increased risk of learning disabilities. Most individuals with this condition have normal fertility.

The condition is generally not inherited but rather occurs as a result of a random event during sperm development. Diagnosis is by a chromosomal analysis, but most of those affected are not diagnosed within their lifetime. There are 47 chromosomes, instead of the usual 46, giving a 47,XYY karyotype.