Congenital disorders of glycosylation (CDG) are a group of clinically heterogenous metabolic disorders that result from defects in the synthesis of glycans and/or the attachment of glycans to proteins and lipids. CDG can be classified into defects in protein N-glycosylation, O-glycosylation, glycosphingolipid and glycosylphosphatidylinositol-anchor and multiple glycosylation pathways defects.Since defirst clinical description in 1980, approximately 170 types of CDG have been identified. CDG is a rapidly growing metabolic disorders and in the last 3 years, 24 new types of CDG were described. Due to the development of new technologies, such as genomic analysis by means of next generation sequencing and other “omics technologies” the CDG number keeps rising. Most CDG types are ultrare disorders. The incidence prevalence of CDG is between 0.1-0.5/100000 population. The clinical spectrum of CDG is extremely broad, covers nearly all known phenotypes. CDG typically is presented with multisystem manifestations(>80%-neurological impairment, 22% -liver, 20% -heart,10% imunologycal,etc.), most commonly developmental delay, failure to thrive, hypotonia,cerebellar atrophy, hepatopathy and coagulopathy.The CDG pathophysiology is complex and the diagnosis is a challenge for clinicians because of the overlapping clinical signs and symptoms that mimics other rare disorders. Therefore, it is strongly recommended that CDG to be considered in any child with an unexplained clinical syndrome.The gold standard in diagnosis of CDG is biochemical screening of suspected patients by Isoelectrofocusing of Transferrin. An important step in diagnosis is to exclude secondary abnormality of glycosylation as galactosemia, fructosemia, liver disease, transferrin polymorphism and others. Abnormal transferrin profiles are an indication for genetic screening with targeted CDG gene panels or genome sequencing to identify pathogenic variants in CDGassociated genes. Many system are affected due to abnormal glycosylation, but there are no disorder-specific treatments and most of the currently available treatment options in CDG are symptomatic. CDG is a group of pathologies with a chameleon phenotype that involves a multidisciplinary team for diagnosis and therapy.