Abundance of serum proteins used as markers for intestinal integrity. (A) Stratified zonulin abundance comparison between individuals with reported GI symptoms and those without. Colors correspond to the underlying phenotypic group (MIS-C: patients with MIS-C; HC: healthy controls; DV: viral controls). Patients with GI symptoms exhibit higher levels of zonulin than patients without (P = 3 × 10⁻¹⁰), Mann–Whitney. (B–D) Calprotectin (B), lipopolysaccharide binding protein (LPB) (C), and fatty acid binding protein 2 (FABP2) (D). Abundance assessed using SomaScan in plasma of acute MIS-C, KD, and DV phenotypes compared with healthy controls. Statistical significance assessed with Mann–Whitney U test (four significance thresholds: *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001).