Compared with those with mild to moderate GI features, children presenting with abdominal pain (OR, 27.9; 95% CI, 12.32-63.4), vomiting (OR, 3.47; 95% CI, 1.93-6.21), leukocytosis (OR, 2.83; 95% CI, 1.51-5.28), lymphopenia (OR, 11.2; 95% CI, 5.63-22.4), elevated C-reactive protein levels (OR, 11.6; 95% CI, 4.97-27.1), or increased ferritin levels (OR, 10.62; 95% CI, 4.61-24.52) had an increased chance of severe GI involvement in univariate analysis (eTable 1 in Supplement 1). The gene discussed is CRP; the disease is lymphopenia.