PHGDH and neurometabolic disorder due to serine deficiency: Thus, mutations in the genes of enzymes participating in the de novo biosynthesis of serine including 3-phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH), coupled by systemic or local serine deficiency, can cause a broad spectrum of phenotypic disorders (9, 10).