Scientific background
Double Y syndrome or 47, XYY syndrome has an incidence of approximately 1:1,000 in male newborns. In most cases, a 47, XYY karyotype is found, and in rare cases, X and Y polysomies. Characteristically, patients show increased height, but are otherwise physically inconspicuous and usually have normal fertility. IQ is mostly normal. Motor development may be slightly delayed. Reading and language difficulties may cause emotional disturbances and reduced frustration tolerance, so that psychological-educational care is advised in childhood if abnormalities are present. Scientific studies have shown that boys and men with an XYY pattern who are in a stable familial environment are not more likely to develop behavioral problems than others. Offspring of XYY males have no increased risk of gonosomal aneuploidies.
References
Ross et al. 2009, Dev Disabil Res Rev 15:309 / Ratcliffe et al. 1999, Arch Dis Child 80:1892 / Bender et al. 1984, Clin Genet 25:435 / Valentine et al. 1997, Birth Defects OAS XV:175