FGF13(Fibroblast growth factor 13), also called FHF2 is a protein that in humans is encoded by the FGF13 gene.The protein encoded by this gene is a member of the fibroblast growth factor (FGF) family. FGF13is a large gene, extending over approximately 200 kb in Xq26.3, and contains at least 7 exons. By cytogenetic, FISH, and database analysis, Gecz et al. (1999) localized the FGF13 gene within a 400-kb duplication interval on chromosome Xq26.3. FGF family members possess broad mitogenic and cell survival activities, and are involved in a variety of biological processes, including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth, and invasion. 

This gene is located to a region associated with Borjeson-Forssman-Lehmann syndrome (BFLS), a syndromal X-linked mental retardation, which suggests it may be a candidate gene for familial cases of the BFL syndrome. The function of this gene has not yet been determined. Two alternatively spliced transcripts encoding different isoforms have been described for this gene.