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 Ik is caused by a defect on chromosome 16p13.3 and involves a defect in the gene for beta-1,4-mannosyltransferase. The disorder is generally fatal within a year or two of birth. See also Congenital disorder of glycosylation type 1K