IDH-DS can first develop up to several months following the initiation of IDH mutant inhibitor treatment for hematologic malignancy and shares distinctive symptomology with the retinoic acid syndrome: culture-negative fever, rapid weight gain or edema, respiratory symptoms with or without infiltrates, pleural or pericardial effusions, hypotension, and acute renal failure (105, 106). The gene discussed is IDH2; the disease is pericardial effusion.