A Rare Case of Myocarditis, Intracardiac Thrombus And Embolic Stroke Caused By Mycoplasma Pneumoniae

Abstract

Introduction Cardiac, thrombotic and neurological complications of Mycoplasma pneumoniae infection are uncommon. We describe a rare case of mycoplasma pneumoniae myocarditis complicated by acute systolic heart failure, left ventricular thrombus and embolic stroke. Case A previously healthy 37-year old man presented with a three-week history of sore throat, orthopnea and exertional dyspnea. Examination revealed an apical systolic 2/6 murmur and bilateral lower extremity pitting edema. He had elevated troponin (0.39 ng/ml, normal 0-0.03 ng/ml) and brain natriuretic peptide (BNP) levels (2500 pg/ml, normal 0-100 pg/ml). Rapid streptococcal Group A test was negative. Electrocardiogram was unremarkable. Chest X-ray revealed cardiomegaly with no evidence of pneumonia or edema. Transthoracic echocardiography showed severe left ventricular dilatation, reduced ejection fraction (10%), moderate to severe mitral regurgitation and an apical left ventricular thrombus. He was managed with diuretics and heparin infusion. Based on the clinical and laboratory findings, a diagnosis of myocarditis with acute systolic heart failure was made. Workup for Epstein-Barr virus, human immunodeficiency virus, cytomegalovirus, coxsackievirus, mycoplasma, serum protein electrophoresis, antinuclear antibody and amyloidosis revealed a positive mycoplasma IgM, so he was started on azithromycin. On the second day of hospitalization, he developed a stroke. MRI brain revealed a large acute infarction in the left middle cerebral artery (MCA) territory and multiple small areas in both cerebral hemispheres consistent with an embolic pattern, likely due to the dislodged emboli from the intracardiac thrombus. MR angiogram head showed left MCA proximal M1 segment occlusion. His elevated international normalized ratio (INR) prevented the administration of recombinant tissue plasminogen activator, so he was placed on therapeutic hypothermia and intubated. He then developed cardiogenic shock and unfortunately passed away. Discussion Extrapulmonary manifestations of mycoplasma pneumoniae may be due to the direct invasion of the bacteria, an autoimmune response or vascular occlusion leading to vasculitis or thrombosis. Macrolides and second generation tetracyclines like doxycycline are the drugs of choice. Further studies are needed to explore the autoimmune mechanism and the use of immunosuppressants. Conclusion A high degree of suspicion for mycoplasma pneumoniae should be maintained in a young patient with features of myocarditis and cardiac thrombus to prevent potentially fatal cardiac and cerebrovascular complications.