XYY syndrome is a chromosome disorder that affects males. Males with this disorder have an extra Y chromosome.
The XYY syndrome was previously considered the super-male syndrome, in which men with this condition were thought to be overly aggressive and more likely to become criminals. These original stereotypes came about because several researchers in the 1960s found a high number of men with XYY syndrome in prisons and mental institutes. Based on these observations, men with XYY syndrome were labeled as overly aggressive and likely to be criminals.
These original observations did not consider that the majority of males with XYY syndrome were not in prisons or mental institutes. Since then, broader, less biased studies have been done on males with XYY syndrome. Though males with XYY syndrome may be taller than average and have an increased risk for learning difficulties, especially in reading and speech, they are not overly aggressive. Unfortunately, some text books and many people still believe the inaccurate stereotype of the supermale syndrome.
Chromosomes are structures in the cells that contain genes. Genes are responsible for instructing our bodies how to grow and develop. Usually, an individual has 46 chromosomes in his or her cells, or 23 pairs. The first 22 pairs are the same in males and females and the last pair, the sex chromosomes, consist of two X chromosomes in a female, and an X chromosome and an Y chromosome in a male.
XYY syndrome occurs when an extra Y chromosome is present in the cells of an affected individual. People with XYY syndrome are always male. The error that causes the extra Y chromosome can occur in the fertilizing sperm or in the developing embryo.
XYY is not considered an inherited condition. An inherited condition usually is one in which the mother and/or father has an alteration in a gene or chromosome that can be passed onto their children. Typically, in an inherited condition, there is an increased chance that the condition will reoccur. The risk of the condition reoccurring in another pregnancy is not increased above the general population incidence.
XYY syndrome has an incidence of one in 1,000 newborn males. However, since many males with XYY syndrome look like other males without XYY syndrome, many males are never identified.
Signs and symptoms
There are no physical abnormalities in most males with XYY syndrome. However, some males can have one or more of the follwing characteristics. Males who have XYY syndrome are usually normal in length at birth, but have rapid growth in childhood, typically averaging in the 75th percentile (taller than 75% of males their same age). Many males with XYY syndrome are not overly muscular, particularly in the chest and shoulders. Individuals with XYY syndrome often have difficulties with their coordination. As a result, they can appear to be awkward or clumsy. During their teenage years, males with XYY syndrome may develop severe acne that may need to be treated by a dermatologist.
Men with XYY syndrome have normal, heterosexual function and most are fertile. However, numerous case reports of men with XYY syndrome presenting with infertility have been reported. Most males with XYY syndrome have normal hormones involved in their sperm production. However, a minority of males with XYY syndrome may have increased amounts of some hormones involved in sperm production. This may result in infertility due to inadequate sperm production. As of 2001, the true incidence of infertility in males with XYY syndrome is unknown.
When XYY men make sperm, the extra Y chromosome is thought to be lost resulting in a normal number of sex chromosomes. As a result, men with XYY syndrome are not at an increased risk for fathering children with chromosome abnormalities. However, some men with XYY syndrome have been found to have more sperm with extra chromosomes than what is found in men without XYY syndrome. Whether these men have an increased risk of fathering a child with a chromosome abnormality is unknown as of 2001.
Men with XYY syndrome usually have normal intelligence, but it can be slightly lower than their brothers and sisters. Approximately 50% of males with XYY syndrome have learning difficulties, usually in language and reading. Speech delay can be noticed in early school years. Males with XYY syndrome may not process information as quickly as their peers and may need additional time for learning.
Males with XYY syndrome have an increased risk of behavior problems. Hyperactivity and temper tantrums can occur more frequently than expected, especially during childhood. As males with XYY syndrome become older, they may have problems with impulse control and appear emotionally immature.
From a psychosocial standpoint, males with XYY syndrome may have low self-esteem due to mild learning disabilities and/or lack of athletic skills due to lack of coordination. Males with XYY syndrome are at risk in stressful environments and have a low ability to deal with frustration.
As of 2001, men with XYY syndrome are not thought to be excessively aggressive or psychotic. However, because some men with XYY syndrome can have mild learning difficulties and/or have difficulty controlling behavior problems such as lack of impulse control, their actions may lead to criminal behavior if placed in the right environment. It is important to emphasize that this occurs only in a small percentage of men with XYY syndrome. Most men with XYY syndrome are productive members of society with no criminal behavior.
Most individuals with 47,XYY go through their entire lives without being diagnosed with this condition. Chromosome studies can be done after birth on a skin or blood sample to confirm the condition. This syndrome can also be diagnosed coincidentally when a pregnant mother undergoes prenatal testing for other reasons, such as being age 35 or older at the time of delivery. Prenatal tests that can determine whether or not an unborn baby will be affected with 47,XXY are the chorionic villi sampling (CVS) and amniocentesis procedures. Both procedures are associated with potential risks of pregnancy loss and therefore are only offered to women who have an increased risk of having a baby born with a chromosome problem or some type of genetic condition.
Treatment and management
Treatment and management for most men with XYY syndrome is not indicated. However, early identification and intervention of learning disabilities and/or behavior difficulties is necessary. Speech therapy, physical therapy, and occupational therapy may be helpful for males with XYY syndrome. Also, because males with XYY syndrome are at risk in stressful environments, a supportive and stimulating home life is important.
Most males who have learning disabilities and/or behavior problems due to XYY syndrome have an excellent prognosis. Learning disabilities are mild and most affected males learn how to control their impulsiveness and other behavior problems. XYY syndrome does not shorten lifespan.
Gotz, M.J., et al. "Criminality and Antisocial Behaviour in Unselected Men with Sex Chromosome Abnormalities." Psychological Medicine 29 (1999): 953–962.
Linden M.G., et al. "Intrauterine Diagnosis of Sex Chromosome Aneuploidy." Obstetrics and Gynecology 87 (1996): 469–75.
Carin Lea Beltz, MS, CGC