Congenital disorders of glycosylation are a rapidly growing group of inherited metabolic diseases. Glycosylation is modification of plasma proteins; during the process, glycoproteins are synthesized. Protein N-glycosylation disorders are the most frequent glycosylation defects. The clinical picture of this disease group is multisystemic, ranging from mild to severe. It is important to search for congenital disorders of glycosylation in every patient with suspected metabolic disease or with unexplained genetic syndrome. We report a case involving the first patient with the diagnosis of congenital disorders of glycosylation in Estonia.