A New Subtype of a Congenital Disorder of Glycosylation (CDG) with Mild Clinical Manifestations

Abstract

A boy with an unspecific symptomatology consisting of mental retardation, strabismus, hypotonia and mild ataxia was diagnosed with a congenital disorder of glycosylation (CDG). Neither cerebellar atrophy nor dysmorphic features were present. The serum transferrin band pattern obtained by isoelectric focusing (IEF) showed a strongly elevated disialotransferrin band together with only slightly elevated asialotransferrin, thus a type 1 pattern. This is a new CDG classified CDG-x since CDG-Ia, -b, -c, -d and -e were excluded. Quantitative differences to the type 1 pattern of a CDG-Ia patient with a moderate to severe course were confirmed by densitometric evaluation of the gels and by SDS gel electrophoresis. Liver biopsy showed lysosomal inclusions suggesting a pre-Golgi defect. This patient's case supports the approach to include isoelectric focusing of serum transferrin in the diagnostic work-up of patients with unexplained symptoms. Congenital disorders of glycosylation · Carbohydrate deficient glycoprotein syndrome · CDG · Isoelectric focusing · IEF · Carbohydrate deficient transferrin