A Case of Myocarditis, Heart Failure, and Left Ventricular Thrombus Caused by Mycoplasma Pneumoniae

Introduction Mycoplasma pneumoniae (MP) is an atypical bacterium that is a common cause of upper respiratory tract infections, bronchitis and community acquired pneumonia. In addition to respiratory symptoms, there are extrapulmonary manifestations which include hematologic, neurologic, dermatologic, and, more rarely, cardiac involvement. The mechanism of extrapulmonary disease is unclear and may be multifactorial. We present a case of a healthy young adult who developed myocarditis and heart failure as well as a left ventricular (LV) thrombus secondary to MP. Case A 32-year-old male with no significant past medical history presented to the emergency department with a 3-day history of anorexia, fever, and a rash after returning from a trip to Colorado. Additionally, he endorsed an 8-pound weight gain and dyspnea on exertion. Upon presentation, he was febrile, tachycardic and had a diffuse targetoid body rash involving his palms and soles consistent with erythema multiforme. Initial labs showed hyponatremia, thrombocytopenia with no leukocytosis. A broad infectious workup was done given his travel history which was significant for a positive mycoplasma IgM confirmed with an immunofluorescence assay. He developed a new oxygen requirement his first night of hospitalization. Chest x-ray showed bibasilar opacities, bilateral pleural effusions, and cardiomegaly. A BNP was drawn due to potential pulmonary edema and was elevated at 1400. A subsequent transthoracic echocardiogram revealed severe global hypokinesis, biventricular enlargement, and eccentric hypertrophy with an ejection fraction of 25%. He then underwent a cardiac MRI, which was consistent with myocarditis and showed an LV apical thrombus. He was started on guideline medical therapy for systolic heart failure, loop diuretics and 4 weeks of doxycycline. He clinically improved and was discharged to follow-up with a plan for a repeat echocardiogram after appropriate time on medical therapy. Conclusion This is an interesting case of mycoplasma associated myocarditis, complicated by heart failure with reduced ejection fraction, and LV thrombus. The etiology of extrapulmonary manifestations of MP has not been fully elucidated and may be related to inflammation, immune modulation, or vascular etiologies. Myocarditis is a rare cardiac manifestation, occurring in approximately 1-5% of patients diagnosed with MP. Development of heart failure and an LV thrombus is an even rarer entity and has been infrequently reported in the literature. This case highlights the importance of recognizing the broad range of extrapulmonary manifestations of MP and seeking out early diagnostic testing of symptomatic patients.