FAS and urea cycle disorder: A pathway analysis for UCD and idiopathic MCD (iMCD) patients discovered that the genes associated with the mitogen-activated protein kinase (MAPK) pathways (fatty acid synthase {FAS}, platelet-derived growth factor receptor B {PDGFRB}, fibroblast growth factor receptor 3 {FGFR3}, neurofibromatosis type 1 {NF1}, and transforming growth factor beta receptor 2 {TGFBR2}) were the most often damaged in UCD [7].