A new missense mutation in FGF23 gene in a male with hyperostosis-hyperphosphatemia syndrome (HHS)

Hyperostosis-hyperphosphataemia syndrome (HHS) is a rare autosomal recessive metabolic disorder, characterized by recurrent painful swelling of long bones, periosteal new bone formation and cortical hyperostosis or intramedullary sclerosis, hyperphosphatemia and low intact fibroblast growth factor 23 (FGF23) protein levels. It is caused by mutations in 2 genes, N-acetylgalactosaminyltransferase 3 (GalNAc-transferase; GALNT3) and FGF23. We have performed mutation analysis of the GALNT3 and FGF23 genes in a patient with HHS and detected a homozygous mutation in exon 3 of FGF23 gene (NM_020638.2: c.471C>A) which results in amino acid change from phenylalanine 157 to leucin (p.F157L) in receptor interaction site.