Notably, variants in other FGF signaling genes are reported to cause phenotypes present in pedigree 91, including hypogonadism, syndactyly, craniofacial dysmorphisms, and developmental delay.34 Moreover, hypogonadism has been reported in Fgf21−/− mice.35 Part of the syndromic phenotype in ENG_CKP is craniosynostosis, a phenotype associated with other FGF signaling genes but not yet KLB. This evidence concerns the gene KLB and hypogonadism.