Drug-induced acute pneumonitis following initiation of flecainide therapy after pulmonary vein isolation ablation in a patient with mitral stenosis and previous chronic amiodarone use

Key Teaching Points•Because of tissue-specific drug accumulation properties, recognizing the association between flecainide and drug-induced acute lung injury is important. Early withdrawal of the offending agent is critical to clinical recovery.•Flecainide-associated lung injury remains a diagnosis of exclusion. Infectious processes and cardiogenic pulmonary edema must be ruled out. A radiographic pattern of bilateral or unilateral opacities with a ground-glass pattern has been described in previous cases of pneumonitis as well as in our patient. The diagnosis must be made rapidly given the potentially severe consequences of misdiagnosis.•The proposed mechanism of injury in flecainide drug toxicity is a cell-mediated immunologic reaction. Corticosteroids are the treatment of choice, and response to them plays a key role in the diagnostic process. •Because of tissue-specific drug accumulation properties, recognizing the association between flecainide and drug-induced acute lung injury is important. Early withdrawal of the offending agent is critical to clinical recovery.•Flecainide-associated lung injury remains a diagnosis of exclusion. Infectious processes and cardiogenic pulmonary edema must be ruled out. A radiographic pattern of bilateral or unilateral opacities with a ground-glass pattern has been described in previous cases of pneumonitis as well as in our patient. The diagnosis must be made rapidly given the potentially severe consequences of misdiagnosis.•The proposed mechanism of injury in flecainide drug toxicity is a cell-mediated immunologic reaction. Corticosteroids are the treatment of choice, and response to them plays a key role in the diagnostic process.