While KAL1 loss-of-function alterations (i.e., deletions and point mutations) are a known cause of X-linked Kallmann syndrome (KS), which is characterized by the association of hypogonadotropic hypogonadism (HH) and anosmia/hiposmia, complete or partial duplications of this gene have not been reported in the literature. Here, ANOS1 is linked to Kallmann syndrome.