XYY syndrome
| XYY syndrome | |
|---|---|
| Other names | 47,XYY |
| Karyotype from a male with 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 |
XYY syndrome, also known as Jacobs 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. The person is generally otherwise normal, including typical rates of 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.
Treatment may include speech therapy or extra help with schoolwork, and outcomes are generally positive. The condition occurs in about 1 in 1,000 male births. Many people with the condition are unaware that they have it. The condition was first described in 1961.