Mutations in the human PI-GT dolichol phosphate mannose synthase (DPMS) catalytic subunit DPM1 (refs 4, 5)—the enzyme that charges DolP with mannose for protein glycosylation—cause congenital disorders of glycosylation1, 6, 7, 8 type 1e resulting in severe phenotypes including developmental delay and vascular abnormalities9. This evidence concerns the gene DPM1 and Global developmental delay.