Congenital disorders of glycosylation (CDG) are a family of inherited disorders caused by defects in the synthesis of glycans, glycoproteins or other glycoconjugates. Congenital disorders of glycosylation (CDG) are a family of inherited disorders caused by defects in the synthesis of glycans, glycoproteins or other glycoconjugates. Glycosylation of proteins is crucial for a proper organ morphogenesis and for an appropriate coagulation system functioning. The neurological system is commonly affected in this type of disorders but cases of CDG with normal neurological development have been recently described. The group of Experimental Hematology and Clinic Oncology of the University of Murcia (Spain) recently described a rare disorder of glycosylation (ALG12-CDG) as the cause of antithrombin deficiency in a patient of 19 years with a history of repaired ventricular septal defect.