Are there carrier forms or lethal forms of Klinefelter's Syndrome

I'm doing a project and I'm required to answer this.
I know there can't be carriers because the syndrome is basically caused by a random mistake, but are there lethal forms? Need help as soon as possible.

You are probably dealing with the most common form, XXY, which is not a lethal chromosomal condition, but there are various forms of it (XXXY, XXXXYY, etc) that have a wide range of symptoms. Some of these conditions can be more serious.