Congenital disorders of glycosylation is a group of very rare inherited metabolic disorder where defective carbohydrate compounds are attached to glycoproteins and thus impairing glycoprotein function. Type 2d is caused by a defect on chromosome 9p13 and involves a defect in the gene for beta-1,4-galactosyltransferase. See also Congenital disorder of glycosylation type 2D