Anti-Kv1.4 Antibody-Associated Myocarditis Refractory to Maintenance Immunosuppressive Therapy: A Case Report
Tsukasa Kato, Ken Miura, Hiroyuki WatanabeAbstract
Background
Anti-Kv1.4 antibody-associated myocarditis is an extremely rare condition and its optimal long-term management remains unclear.
Case Summary
A 66-year-old woman presented with myasthenia gravis-like symptoms, marked creatine kinase elevation, leukopenia, and hypogammaglobulinaemia. She developed acute myocarditis with ventricular arrhythmias and a reduced left ventricular ejection fraction. Intravenous immunoglobulin and corticosteroid therapy resulted in rapid clinical and cardiac improvement. During cautious tapering of oral prednisolone, she was readmitted with febrile neutropenia and subsequently developed progressive ventricular dysfunction and cardiogenic shock. Cardiac magnetic resonance imaging demonstrated extensive myocardial fibrosis, and autopsy revealed diffuse lymphocytic infiltration. Postmortem testing confirmed positivity for anti-Kv1.4 antibodies.
Discussion
This case highlights the potentially fatal course of suspected anti-Kv1.4 antibody-associated inflammatory myocardial disease despite an initial favourable response to immunosuppressive therapy. It illustrates the diagnostic and therapeutic challenges of distinguishing immune-mediated progression from other causes of myocardial injury and implies the need for individualised long-term management strategies.