SRD5A3-CDG: a patient with a novel mutation.

Congenital disorders of glycosylation (CDG) are genetic diseases with an extremely broad spectrum of clinical presentations due to defective glycosylation of glycoproteins and glycolipids. Some 45 CDG types have been reported since the first clinical description in 1980. Protein glycosylation disorders are defects in protein N- and/or O-glycosylation. Dolichol phosphate is the carrier of the N-glycan during their assembly first at the outside and subsequently at the inside of the endoplasmic reticulum (ER) membrane, and hence is a key molecule in protein glycosylation. Recently, defects have been identified in the last three steps of the dolichol phosphate biosynthesis: dolicholkinase deficiency (DK1-CDG), steroid 5alpha-reductase type 3 deficiency (SRD5A3-CDG), and dehydrodolichyl diphosphate synthase deficiency (DHDDS-CDG). We report on a patient with SRD5A3-CDG carrying a novel (homozygous) mutation. The diagnostic features of this novel inborn error of glycosylation are psychomotor retardation, nystagmus, visual impairment due to variable eye malformations, cerebellar abnormalities/ataxia, and often ichthyosiform skin lesions.