Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Klinefelter's Syndrome ?
    ### Response:
    Klinefelter syndrome (KS) is a condition that occurs in men who have an extra X chromosome. The syndrome can affect different stages of physical, language, and social development.    The most common symptom is infertility. Boys may be taller than other boys their age, with more fat around the belly.
    