• Echocardiography
• infective endocarditis

A 34-year-old man was admitted for recurrent fever and non-productive cough for 2 months. He suffered from an advanced adenocarcinoma of the lung with lung to lung and lumbar spine metastases. He had received palliative chemotherapy and radiotherapy. There was no history of drug abuse.

Echocardiography was performed due to persistent bacteraemia with methicillin-resistant Staphyloccus aureus. There was a large vegetation over the tricuspid valve, which was highly mobile (figure 1 and online supplementary movie 1). Another small vegetation was noted over the rim of an interatrial septal aneurysm, which came into contact with the large vegetation during systole (figure 2 and online supplementary movie 2).

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Figure 1

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Figure 2

An interatrial septal aneurysm is usually asymptomatic and diagnosed incidentally by echocardiography. Pathology study has revealed fibrosis and a mural thrombus on the anerusymal surface, which might account for the embolism in some young patients with ischaemic stroke. In the present case, we reported a very rare vegetation on the rim of the interatrial aneurysm. The irregular surface of the interatrial aneurysm might provide the nidus for seeding and growth of vegetation originating from the tricuspid valve.