Does a child have klinefelter syndrome due to his own mutation or due to mutations his parents carry?

Extra X chromosome: There is not a mutation in the conventional sense as none of the genes are abnormal. The phenotypic male, with a y chromosome, has more than on x chromosome, associated with poor testicular development, infertility and obesity.

New mutation: Klinefelter syndrome happens in males who have an extra x chromosome (xxy). It happens when there is an error in separation of the "sex chromosomes, "50% of the time in the mother's cells of reproduction and 50% of the time in the father's. Learning and behavior problems often occur along with the physical/ medical problems. There is a national parent support group.