Carbohydrate-deficient glycoprotein syndrome type IA (phosphomannomutase-deficiency)

The carbohydrate-deficient glycoprotein or CDG syndromes (OMIM 212065) are a recently delineated group of genetic, multisystem diseases with variable dysmorphic features. The known CDG syndromes are characterized by a partial deficiency of the N-linked glycans of secretory glycoproteins, lysosomal e nzymes, and probably also membranous glycoproteins, Due to the deficiency o f terminal N-acetylneuraminic acid or sialic acid, the glycan changes can b e observed in serum transferrin or other glycoproteins using isoelectrofocu sing with immunofixation as the most widely used diagnostic technique. Most patients show a serum sialotransferrin pattern characterized by increased di- and asialotransferrin bands (type I pattern). The majority of patients with type I are phosphomannomutase deficient (type IA), while in a few othe r patients, deficiencies of phosphomannose isomerase (type IB) or endoplasm ic reticulum glucosyltransferase (type IC) have been demonstrated. This rev iew is an update on CDG syndrome type IA. (C) 1999 Elsevier Science B.V. Al l rights reserved.