Oral mannose therapy persistently corrects the severe clinical symptoms and biochemical abnormalities of phosphomannose isomerase deficiency.

Phosphomannose isomerase (PMI) deficiency (CDG-Ib) is a newly recognized disorder of mannose and glycoprotein metabolism. PMI deficiency manifests itself mainly as a gastrointestinal disorder with protein-losing enteropathy and life-threatening intestinal bleeding. Hypoglycaemia is an additional prominent symptom.