The most common congenital glycosylation disorder (CGD) is in fact PMM2 deficiency (PMM2-CDG, MIM#212065), which was formerly known as Congenital Disorder of Glycosylation-Ia, CDG-Ia, or Jaeken syndrome; no CDG described so far is linked to mutations of PMM1. Here, PMM2 is linked to PMM2-congenital disorder of glycosylation.