47XYY

47,XYY syndrome is a sex chromosome aneuploidy in males in which an extra Y chromosome is present, giving a karyotype of 47,XYY compared with the typical 46,XY. The extra Y usually results from nondisjunction during paternal meiosis and is typically present in all cells. The condition is sometimes referred to as Jacob’s syndrome.

Prevalence and presentation vary. It occurs in about 1 in 1,000 live-born male births, and many individuals are never diagnosed. Most with 47,XYY are tall relative to peers. Genital development and puberty are usually normal, and fertility is commonly unaffected. Cognitive and developmental outcomes are variable: many have average intelligence, but some experience mild learning disabilities, speech and language delays, and coordination difficulties. There is some association with higher rates of attentional or behavioral differences, including attention-deficit/hyperactivity disorder or autism spectrum disorders, but these associations are not universal and vary among individuals.

Diagnosis and management rely on genetic testing. The condition is confirmed by chromosomal analysis (karyotyping) of blood or other tissue, and can be detected prenatally through procedures such as amniocentesis or chorionic villus sampling. Management is supportive and multidisciplinary, focusing on early intervention, speech and language therapy, occupational therapy, and educational support as needed. Genetic counseling is offered to discuss the low likelihood of recurrence, since most cases arise de novo and parental recurrence risk is considered to be similar to that of the general population.

Prognosis is generally favorable, with many individuals leading typical lives. Life expectancy is not typically affected.