PMM2 and liver disorder: The authors classified CDG based on liver involvement into two main groups: one with predominant/isolated liver involvement (MPI-CDG, CCDC115-CDG, TMEM199-CDG, ATP6AP1-CDG) and the other associated with liver disease (PMM2-CDG, ALG1-CDG, ALG3-CDG, ALG8-CDG, ALG9-CDG, PGM1-CDG).