CMAS and infection: Of note, previous reports showed that the urinary levels of sialic acid, the terminal glycan of sLex structure, discriminate patients with active TB from healthy controls or patients with non-tuberculous pulmonary diseases.35 Also, the regulation of the gene encoding CMAS, the enzyme that provides the substrate for the addition of sialic acid, specifically changed with infection with Mtb. 36 Thus, modulation of sialylated antigens seems to occur in TB, as described in several pathologies, such as other infectious diseases and cancer.6,16,17,37