When Common Presentations Conceal Rare Diagnoses: A Case Report of Splenic Actinomycosis.

Splenic abscess secondary to Actinomyces species is an exceedingly rare condition that presents with a constellation of nonspecific symptoms often leading to delayed presentation, diagnostic uncertainty, and misidentification. While Actinomyces is typically an indolent infection, splenic abscess has a high mortality when untreated due to the risk of splenic rupture. This case report highlights a rare instance of isolated Actinomyces splenic abscess in a 52-year-old man with a history of intravenous drug use, hepatitis C, and recent incarceration who presented with several weeks of hemoptysis, fevers, night sweats, pleuritic chest pain, and left upper quadrant abdominal pain. The history and clinical presentation were most concerning for malignancy, tuberculosis, or other pulmonary infectious etiologies. Computed tomography imaging revealed a 14.9 x 7.7 x 12.1 cm splenic abscess with associated pleural effusion. A percutaneous drain was placed by interventional radiology, and the resulting fluid culture grew Actinomyces meyeri. In consultation with infectious disease specialists, prolonged antibiotic therapy was started with four weeks of intravenous piperacillin-tazobactam followed by six months of oral amoxicillin. This case highlights both the diagnostic challenge of splenic actinomycosis and the importance of maintaining a broad differential diagnosis to avoid anchoring bias or early diagnostic closure in high-risk patients with nonspecific symptoms.