Synonyms: Double Y syndrome | Jacobs syndrome | XYY syndrome | Y disomy
A rare sex chromosome aneuploidy where males receive an additional Y chromosome that is characterized clinically by tall stature evident from childhood macrocephaly facial features (mild hypertelorism low set ears a mildly flat malar region) speech delay and an increased risk for social and emotional difficulties attention deficit hyperactive disorder and autistic spectrum disorder.
Data from Orphanet are used to provide information on a disease's name, synonym(s), and overview. Reference: Access aggregated data from Orphanet at Orphadata. Orphadata: Free access data from Orphanet. © INSERM 1999. Available on http://www.orphadata.org. Data version April 2026
Newly diagnosed with
47,XYY syndrome?
Our RARE Concierge Services Guides are available to assist you by providing information, resources and connections as you navigate your rare disease journey.
Advocacy Organizations
AXYS
AXYS, the Association for X and Y Chromosome Variations, is an advocacy, education and support organization for individuals with X and Y chromosome variations and their families. This includes those with Klinefelter syndrome (47,XXY), Trisomy X (47,XXX), 47,XYY, 48,XXYY, 48,XXXY and related genetic conditions. The mission of AXYS is to help individuals with one or more extra X and/or Y chromosomes
Rare Chromosome Disorder Support Group – Unique
Through sharing knowledge and lived experience, Unique helps families and professionals navigate the world of chromosome and gene disorders
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Clinical Trials
For a list of clinical trials in this disease area, please click here.