Phosphomannomutase 2 (PMM2) deficiency, the most frequent congenital disorder of glycosylation (PMM2-CDG), is a severe condition, which has no cure. Due to the identification of destabilizing mutations, our group aims at increasing residual activity in PMM2-CDG patients, searching for pharmacochaperones. Detailed structural knowledge of hPMM2 might help identify variants amenable to pharmacochaperoning. hPMM2 structural information is limited to one incomplete structure deposited in the Protein Databank without associated publication, which lacked ligands and residues from a crucial loop. Here we report five complete crystal structures of hPMM2, three for wild-type and two for the p.Thr237Met variant frequently found among Spanish PMM2-CDG patients, free and bound to