Myasthenia gravis complicated by myocarditis associated with anti-titin and anti-VGKC antibodies: a case report

Myasthenia gravis (MG) is an autoimmune neuromuscular junction disorder primarily affecting skeletal muscles. Although myocardial involvement is rare, MG-associated myocarditis can be life-threatening and may be overlooked because symptoms such as dyspnea and fatigue overlap with myasthenic exacerbation. Recognition of clinical and immunological features associated with cardiac involvement is therefore important for early diagnosis and appropriate management. We report a case of MG complicated by myocarditis in a 74-year-old woman with a chronic course and acute exacerbation. She presented with a 2-year history of ptosis with acute worsening over the preceding 20 days, including dysphagia, limb weakness, and respiratory distress. Cardiac biomarkers were mildly elevated (peak troponin I 2.19 µg/L, creatine kinase-MB (CK-MB) 30 µg/L, N-terminal pro-brain natriuretic peptide (NT-proBNP) 4581 ng/L), echocardiography revealed a reduced left ventricular ejection fraction (42%) with segmental wall motion abnormalities but no structural changes, and coronary computed tomography angiography (CTA) demonstrated only mild atherosclerosis. Serological testing was positive for anti-acetylcholine receptor (AChR), titin, anti-cardiac, and voltage-gated potassium channel (VGKC) antibodies. After treatment with pyridostigmine, intravenous immunoglobulin, tacrolimus, and low-dose corticosteroids, respiratory distress and dysphagia resolved, cardiac biomarkers and ejection fraction normalized within days, and Electrocardiogram (ECG) changes fully resolved by 4-month follow-up. This case highlights the importance of considering myocarditis in MG patients presenting with respiratory difficulty, with prompt ECG monitoring and cardiac enzyme assessment to detect occult cardiac involvement.