Tumoral Calcinosis Presenting with Eyelid Calcifications due to Novel Missense Mutations in the Glycosyl Transferase Domain of the<i>GALNT3</i>Gene

Abstract

Previously reported GALNT3 mutations in TC have been null mutations. This study shows that missense mutations affecting the glycosyl transferase domain of GalNAc transferase 3 also cause TC. Elevated C-terminal FGF23 fragments with undetectable intact FGF23 suggest that the mutant enzyme lacks the ability to glycosylate FGF23 and that glycosylation by GalNAc transferase 3 is necessary for secretion of functional full-length FGF23.