Case Report: Pericardial Actinomycosis in a 79-Year-Old Man with Poor Dental Hygiene.

Actinomycosis is an uncommon infection caused by Actinomyces species, and the diagnosis is often challenging owing to low prevalence and diverse clinical manifestations. Pericardial involvement of actinomycosis is particularly rare. Here, we present a case of a 79-year-old man who initially complained of exertional dyspnea, orthopnea, and decreased urine amount. There was no fever, chest pain, or productive cough. Physical examination was remarkable for decreased breath sounds at the left lower lung field. Poor dental hygiene and a firm, well-defined mass without discharge over the hard palate were noted. Echocardiography revealed reduced ejection fraction of the left ventricle, global hypokinesia, and thickened pericardium (> 5 mm) with a small amount of pericardial effusion. On admission, the patient underwent diagnostic thoracentesis, and the results suggested an exudate. However, bacterial and fungal cultures were all negative. There was no malignant cell by cytology. Computed tomography revealed contrast-enhanced pericardial nodular masses. Video-assisted thoracoscopic pericardial biopsy was performed. Histopathology confirmed actinomycosis with chronic abscess formation, and a tissue culture yielded Aggregatibacter actinomycetemcomitans. The symptoms resolved with administration of clindamycin for 6 months. This case highlights the challenge in the diagnosis of cardiac actinomycosis, the potential role of concomitant microorganisms as diagnostic clues, and the favorable clinical response achieved with appropriate antibiotic treatment.