What genetic syndrome is characterized by a male with an extra X chromosome?

Klinefelter syndrome is characterized by the presence of an extra X chromosome in males, resulting in a typical chromosomal pattern of 47,XXY. This genetic condition arises during meiosis when an error occurs, leading to the formation of sperm or egg cells that carry an extra X chromosome.

Individuals with Klinefelter syndrome often exhibit a range of physical and developmental traits, which can include tall stature, gynecomastia, reduced muscle mass, and fertility issues. Consequently, the recognition of this syndrome is critical in pediatric neurology because of the potential neurodevelopmental impacts and associated behavioral features that may arise, which can benefit from early intervention.

In contrast, Turner syndrome primarily affects females with a missing or incomplete X chromosome and thus does not involve the presence of an extra X chromosomal element in males. Down syndrome is typically caused by an additional copy of chromosome 21, unrelated to the X chromosome abnormalities seen in Klinefelter syndrome, while Fragile X syndrome is a distinct genetic condition associated with mutations in the FMR1 gene, which is unrelated to the chromosomal count but can affect cognitive development and behavior.