Klinefelter syndrome is a genetic condition that affects males and occurs when a boy is born with an extra X chromosome. This extra chromosome can interfere with male sexual development and fertility, leading to smaller than normal testicles, lower production of testosterone, reduced muscle mass, reduced body and facial hair, and enlarged breast tissue. The effects of Klinefelter syndrome vary, and not everyone has the same signs and symptoms. Signs and symptoms of Klinefelter syndrome also vary by age. Babies with Klinefelter syndrome typically have weak muscles, reduced strength, and quiet personalities, and they can take longer to do things like sit up, crawl, walk, and speak. Boys with Klinefelter syndrome might have a taller, less muscular body, broader hips and longer legs and arms, larger breasts (a condition called gynecomastia), weaker bones, a lower energy level, and smaller penis and testicles. Klinefelter syndrome is not caused by anything the parents did or did not do, and it is a random error in cell division that happens when a parents reproductive cells are being formed. There is no cure for Klinefelter syndrome, but some of the problems associated with the condition can be treated if necessary. Possible treatments include hormone replacement therapy, speech and language therapy during childhood to help with speech development, educational and behavioral support at school to help with any learning difficulties or behavior problems, and occupational therapy to help with any coordination problems associated.