XYYSyndrome to drink a glass of water. Occasionally,a
XYYSyndrome is a rare genetic disorder which affects males due to an extra Y chromosome.
Healthy males have 46 chromosomes including one X and one Y chromosome. Menwith XYY syndrome have 47 chromosomes, two of which are Y chromosomes. Itis not known why the extra Y chromosome occurs. The disorder is present atbirth and is estimated to occur in one out of every one thousand live births.
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In very rare instances, the syndrome has been passed from father to son, butin most cases heredity cannot be established. The characteristics ofXYY syndrome are often very subtle and do not indicate and serious chromosomaldisorder. Therefore, males with this condition are frequently undiagnosedor misdiagnosed. The primary symptoms include tall or very tall height whichbecomes evident at the age of five or six, and severe cystic acne during adolescence.
Lowerthan average intelligence and/or behavioral problems, such as an explosivetemper, aggressive or defiant actions, or sometimes antisocial behavior areother symptoms. Some individuals with this disorder may also have languagedifficulties or psychosexual problems. XYY Syndrome is often undiagnosed untiltests for other medical reasons are performed. Other than being unusuallytall and/or having behavioral problems, in many cases, these boys or men appearnormal.
Physical characteristics of XYY Syndrome may include an exceptionallylong head with a slightly protrusive forehead, long hands and feet, long ears,mild indentation of the breastbone, and/or large teeth. Poor chest and shouldermuscle development is also common. Even though males with this syndrome arelarge, they tend to be weak and uncoordinated.
Some may have a fine intentionaltremor, such as shaking hands when the try to drink a glass of water. Occasionally,a bony formation across the joints in the two bones of the forearm resultingin the stiffening of the affected joints may occur. Other occasional symptomsare undescended testicles, a small penis, or an opening located on the undersideof the penis.For a long time it was thought that XYY Syndrome individualshad aggressive tendencies often associated with criminal behavior due to theextra Y chromosome.
Epidemiological studies suggest that one out of every35 institutionalized male juvenile delinquents has XYY Syndrome. However,it is now believed by some researchers that this behavior is not due to theextra Y chromosome, but rather to the lower than average intelligence and educationlevels of these men. More research is needed to understand the role of thischromosomal abnormality on behavior.