what is the chance of being born with klinefelter syndrome?
Klinefelter syndrome is the most common sex-chromosome abnormality, affecting about one in every 500 to 700 men. What causes Klinefelter syndrome? The addition of extra chromosomes seems to occur by chance. The syndrome is not inherited from the parents. The addition occurs in the sperm, the egg, or after conception. What are the signs and symptoms of Klinefelter syndrome? Signs and symptoms can vary.