Our group focuses on the study of sialic acid and sialylated glycans in inflammatory diseases. In this work, we aim to find better biomarkers for severity stratification in post-viral syndrome using a glycomics approach. Glycomics is the communication language of organisms, based on a sugar code (glycans) imprinted on tissues, proteins, and lipids. Many diseases, such as autoimmune disorders and pathogenic infections, has an alterered sugar code in the organism, leading to inflammation. N-glycome was characterized in serum and purified IgG by MALDI mass spectrometry in positive mode after purification and derivatization with methylamine. After labelling with DMBA, total sialic acid content was quantified by HPLC-RP-FL. We observed variations in N-glycome and sialic acid concentration between patients and controls, suggesting the involvement of sialic acid in the severity of post-viral fatigue syndrome.