Miglustat inhibits glucosylceramide synthase (GCS, or UDP-glucose:ceramide glucosyltransferase), the first enzyme in the GSL biosynthesis pathway, in order to reduce synthesis of glucosylceramide that accumulates in Gaucher's disease (GD, MIM 230800), a disorder of the defective hydrolase β-glucosylceramidase (GCase or GBA1) which is essential for sphingolipid degradation. Here, UGCG is linked to Gaucher disease.