A 42-year-old woman with supraventricular tachycardia status post ablation, factor V Leiden (FVL) heterozygosity, migraine, and hyperlipidemia presented with severe headaches, left-sided homonymous hemianopia and brief episode of left arm numbness. She was subsequently found to have an acute right parieto-occipital infarct.

Over the following ten months, she had six additional cryptogenic embolic strokes with debilitating neurological deficits despite medical management with different anti-thrombotic agents. She also continued to have recurrent seizures, headaches and chills with night sweats. Imaging with MR and CT angiography along with conventional angiogram did not reveal any intrinsic vascular abnormality. An extensive neuro-rheumatologic workup including lumbar puncture and hypercoagulability markers was also negative (except for FVL heterozygosity). An elaborative cardiac workup with several transthoracic (TTE) and transesophageal echocardiograms (TEE) was initially inconclusive for intra-cardiac shunt, thrombus or vegetation. However, nine months after her initial presentation, a TEE revealed small, hypermobile, filamentous masses on the mitral valve. Blood cultures throughout her disease course remained negative.

Ultimately, an elevated serum legionella pneumophila IgG titer (1:512) was found, without concurrent gastrointestinal or lung disease. Treatment with levofloxacin led to significant clinical improvement without recurrence of headaches, strokes, or seizures. Follow-up TEE showed reduced size of the filamentous structures and legionella titers decreased. The source of her infection remains unclear.

Legionella endocarditis can result in devastating neurological complications. A high clinical index of suspicion should be maintained for accurate diagnosis and successful treatment.