Methylmalonic acidemia, phenylketonuria, and primary carnitine deficiency were the major IEMs and the mutations in PAH, SLC22A5, and MMACHC genes are the leading causes of IEMs resulting in phenylketonuria, primary carnitine deficiency, and methylmalonic acidemia, respectively, in Jining area. The gene discussed is SLC22A5; the disease is phenylketonuria.