A case of asthma-complicated influenza myocarditis

A 36-year-old man with a history of asthma visited an outpatient clinic complaining of high fever and general fatigue, and was diagnosed as having influenza type A by influenza antigen test. Laboratory findings revealed mild inflammation, mild acidemia, and hypercapnea with radiologic infiltrations in the right lung, and remarkable wheezes in both lungs were heard on auscultation. He was diagnosed with asthma exacerbation and having influenza pneumonia, and was referred to us. Therapy was begun with oseltamivir for influenza infection and intravenous infusions of betamethasone and aminophylline with non-invasive pulmonary ventilation for asthma exacerbation and acute respiratory failure. Although he was weaned from mechanical ventilation and his general condition became good, electrocardiogram showed sinus bradycardia and negative T waves in V1-4 without any symptoms. Blood test and echocardiography showed almost normal findings except for slight elevation of LDH and AST. Influenza A antigen was already confirmed and he was diagnosed as having influenza myocarditis clinically. Although it is well known that influenza can cause asthma exacerbation and encephalopathy, influenza myocarditis is regarded as rare by physicians. In fact, the number of case reports about influenza myocarditis is few. Myocarditis may not appear to be serious, but could cause fatal arrhythmia and heart failure. All clinicians should be aware of the overall clinical picture and the possibility of severe complications of myocarditis caused by flu infection.