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 IIf is caused by a defect on chromosome 6q25.16q15 and involves a defect on the gene for CMP-sialic acid transporter. See also Congenital disorder of glycosylation type 2F