PROK2 and congenital hypogonadotropic hypogonadism: To date, digenic inheritance of KS has been shown in few patients who had monoallelic missense mutations both in PROKR2 or PROK2, and in other KS genes (KAL1, FGFR1) or genes underlying normosmic congenital hypogonadotropic hypogonadism (GNRHR, KISS1R) (Dodé et al., 2006; Cole et al., 2008; Raivio et al., 2009; Martin et al., 2010; Sarfati et al., 2010).