Double trouble: Mycoplasma pneumoniae and its unexpected complications

This case highlights a rare and life-threatening presentation of Mycoplasma pneumoniae infection, demonstrating its potential to cause severe systemic complications beyond the respiratory tract. While often considered a mild illness, M. pneumoniae can contribute to thrombotic events, cardiac arrhythmias, and organ infarctions—complications that are under-recognized in clinical practice.

A 43-year-old man presented with cardiogenic shock caused by atrial flutter, resistant to rate-controlling medications, necessitating electrical cardioversion. Imaging revealed thrombi in both ventricles, with the left-sided thrombus posing a high embolic risk. A right-sided intracardiac mass initially suspected to be infective endocarditis was later confirmed as thrombus via computed tomography (CT) imaging, highlighting the role of advanced imaging in differential diagnosis. The patient also developed necrotizing pneumonia and splenic infarction. He was treated with antibiotics, anticoagulation, heart failure therapy, and scheduled follow-up. The aetiology of the biventricular thrombi remains unclear, likely multifactorial—either due to M. pneumoniae-induced hypercoagulability, biventricular dysfunction, or both.

Physicians should be aware that M. pneumoniae is not always a benign infection. It can provoke severe cardiac and thrombotic complications, even in immunocompetent adults. Intracardiac thrombi, in particular, may be overlooked, and CT imaging can be an important diagnostic tool when endocarditis is suspected. Early recognition and aggressive multidisciplinary management are essential for improving outcomes in such complex presentations.