PHGDH and microcephaly: The deficiency of 3-phosphoglycerate dehydrogenase (3-PGDH) is the most reported defect that causes serine deficiency disorders, a group of neurodevelopmental, neurometabolic disorders with congenital microcephaly, intractable seizures and severe psychomotor retardation (van der Crabben et al., 2013), implicating the pathological relevance of this pathway.