CDG syndrome is the abbreviation for "Congenital Disorders of Glycosylation". CDG are rare inherited metabolic conditions which affects human development and physiology. They often causes extremely serious, and possibly fatal, medical problems to infants. CDG are classified as CDG type-I and type-II, depending on the localization of the biochemical defect. Currently, twelve CDG type-I variants have been identified and named CDG-Ia to CDG-IL, wheather only four variants of CDG Type-II have been described (CDG-IIa to -IId). They are all caused by abnormal synthesis of the sugar groups which form parts of glycoproteins which, in turn, leads to disorders of the nerves, liver and intestines. The specific effects differ according to the particular abnormal synthesis involved.