Mutations in three genes encoding enzymes in the Leloir pathway, namely GALT (MIM: 606999), GALK1 (MIM: 604313), and GALE (MIM: 606953), have been associated with three genetic galactosemias: GALT deficiency (MIM: 230400), GALK1 deficiency (MIM: 230200), and GALE deficiency (MIM: 230350), respectively. Here, GALT is linked to classic galactosemia.