MPI and disorder of copper metabolism: CDG disease is triggered by gene defect of the coiled-coil domain containing 115 (CCDC115), transmembrane protein 199 (TMEM199), ATPase H+ transporting accessory protein 1 (ATP6AP1), and mannose phosphate isomerase (MPI), and is mainly manifested by varying degrees of liver injury, possibly leading to copper metabolism disorder by affecting the glycosylation modification of ATP7B protein (22, 23).