Novel GALNT3 Mutations Causing Hyperostosis-Hyperphosphatemia Syndrome Result in Low Intact Fibroblast Growth Factor 23 Concentrations

Abstract

The presence of GALNT3 mutations and elevated C-terminal, but low intact serum FGF23, levels in HHS resemble those seen in TC, suggesting that HHS and TC are different manifestations of the same disorder. The absence of biochemical abnormalities in the heterozygous individuals suggests that one normal allele is sufficient for secretion of intact FGF23.