Spectrum of age-dependent clinical signs and abnormal biochemical results (routine laboratory, serum glycoproteins and their isoforms proportion) underline the screening of congenital defects of glycosylation (CDG). Abnormalities found by histology and various imaging methods may be helpful for the diagnostics. Decrease of particular enzymes activity in leukocytes and mutation analysis are fundamental for demonstration and precise typing of the defect.

        Key words: glycoproteins, defect of glycosylation, CDG, inherited metabolic disorders, diagnostics