Severely ill COVID-19 patients often display increased plasma levels of indicators of intestinal permeability, such as zonulin, a mediator of tight junctions in the digestive tract, fatty acid binding protein 2 (FABP2), lipopolysaccharide (LPS), and peptidoglycan (PGN), indicating a compromised intestinal barrier (251, 253). The gene discussed is FABP2; the disease is COVID-19.