SLC22A5 and systemic primary carnitine deficiency disease: 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.