Endocrine Abstracts

Klinefelter syndrome (KS) was first described in 1942 and the cause for the syndrome was identified as a supernumerary X chromosome resulting in the karyotype 47,XXY. 80–90% of KS cases bear this karyotype, whereas the remaining exhibit (in decreasing frequency) varying mosaicism (e.g. 47,XXY/46,XY), carry additional sex chromosomes (48,XXXY; 48,XXYY; 49,XXXXY) or structurally abnormal X chromosomes. The prevalence of KS is up to 1 in 500 boys, and it is the most common c...