XYY syndrome typically causes no unusual physical features or medical problems. Males with this syndrome may be slightly taller than average and are typically a few centimeters taller than their father and siblings.
Skeletal malformations may also accompany XYY syndrome at a higher rate than in the general population. Severe facial acne has occasionally been reported, but dermatologists specializing in acne (Plewig & Kligman, 2000) now doubt the existence of a relationship with XYY. Several other physical characteristics, including large hands and feet, have been associated (although not definitively) with XYY syndrome. Any physical characteristics, however, are usually so slight that they are insufficient evidence to suggest a diagnosis.
Most males with XYY syndrome have normal sexual development and are able to conceive children.
Since there are no distinct physical characteristics, the condition usually is only detected during genetic analysis for other reasons.
A fellow editor requested that someone provide references or some sources for the information in this section. XYY boys have an increased risk of minor speech and motor skill delays and learning disabilities with roughly half requiring some special education intervention. Behavior problems are common, but are not unique to XYY boys and are managed no differently than in XY boys. There have been suggestions of elevated frequency of XYY genotype in inmates and delinquents. A common myth is that the Y Chromosome (male sex chromosome) adds to the aggression and antisocial behavior of people who have this syndrome. No clear evidence exists of it leading to aggression. However, scientists have...