Klinefelter

Klinefelter syndrome (also known as 47,XXY or XXY syndrome) is a set of symptoms that result from two or more X chromosomes in males. The primary features are sterility and small testicles. Often symptoms may be subtle and many people do not realize they are affected. Sometimes, symptoms are more prominent and may include weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex. Often it is only at puberty that these symptoms are noticed. Intelligence is usually normal; however, reading difficulties and problems with speech are more common. Symptoms are typically more severe if three or more X chromosomes are present.

Causes

Klinefelter syndrome usually occurs randomly. An older mother may have a slightly increased risk of a child with Klinefelter syndrome. The syndrome is not inherited from a person's parents. The extra X chromosome is retained because of a nondisjunction event during paternal or maternal meiosis I (gametogenesis). Nondisjunction occurs when homologous chromosomes, in this case the X and Y or two X sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome or an egg with two X chromosomes. Hence, males with Klinefelter syndrome are usually 47,XXY or one of its variants. Males with Klinefelter syndrome are still genetically male, and often will not realize they have this extra chromosome, but they will have a tendency to develop a less muscular body, less facial and body hair, and broader hips than other men. Because of the extra chromosome, individuals with this condition are usually taller than average.

Diagnosis

Diagnosis can be made based on physical characteristics, blood work, and genetic testing. Klinefelter syndrome often goes undiagnosed in males due to the often-subtle symptoms. In adults, possible characteristics vary widely and include little to no signs of affectedness, a lanky, youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue). Gynecomastia is present to some extent in about a third of affected individuals, a slightly higher percentage than in the XY population. Reduced muscle strength characterizes around 80% of affected individuals, and about 10% have a rounded body type with increased fat.

Treatment

While there is currently no cure for Klinefelter syndrome, the condition can be managed through a variety of treatment strategies. These may include physical therapy, speech therapy, counseling, and educational support. Testosterone replacement therapy can also be used to treat some of the symptoms associated with the condition, such as decreased muscle mass and reduced bone density.

See also

• Androgen insensitivity syndrome
• Turner syndrome
• Triple X syndrome
• XYY syndrome