FGF23 and familial hyperphosphatemic tumoral calcinosis/hyperphosphatemic hyperostosis syndrome: Hyperphosphatemic familial tumoral calcinosis (HFTC) (online Mendelian inheritance in man (OMIM) 211900) is an autosomal recessive disease caused by mutations in the genes encoding the following proteins: fibroblast growth factor 23 (FGF23, 12p13.3), UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferase-T3 (GALNT3), and Klotho (KL) (1, 4–6).