Congenital disorders of glycosylation (CDG) represent a group of inborn errors of metabolism with multisystem damage determined by the disruption of the glycosylation process. The primary system affected in 80% of cases is the central nervous system, which encompasses a variety of clinical symptoms from mild muscular hypotonia to severe psychomotor retardation, treatment-resistant seizures, and cortical/ cerebellar MRI brain changes. The variety of clinical manifestations often mimics other pathologies, which results in the underdiagnosis of CDG. Many metabolic disorders include similar signs and symptoms, and comparisons can be helpful for a thorough and accurate differential diagnosis. Urea cycle disorders, inborn errors of bile metabolism, fatty acid oxidation disorders, organic acidosis, peroxisome biogenesis disorders, and sphingolipidoses are recommended to be included in the differential diagnosis algorithm of glycosylation disorders. At the same time, patients who present clinical signs under the guise of Infantile cerebral palsy, need to be tested for CDG through the screening method of Isoelectric focusing of transferrin (IEFT). Prader-Willi, Smith-Lemli-Opitz, Weaver, and Robinow syndromes, but also some congenital coagulation disorders, Ataxia-telangiectasia, and other hereditary ataxias, show a clinical picture similar to congenital glycosylation disorders. The IEFT represents a tool with an imposing applicative value in the diagnosis of CDG, that comes to the aid of clinicians, for the differential diagnosis of neurological genetic pathologies.