Inflammatory Pseudotumor Due to Actinomycosis Simulating Post-Transplant Lymphoproliferative Disorder

Hepatic actinomycosis is a rare infection caused by anaerobic, gram-positive Actinomyces bacteria. Liver involvement represents 5% of all actinomycosis cases and usually occurs secondary to intra-abdominal infections, spreading via the porto-mesenteric venous system. Clinical symptoms and imaging findings are typically heterogeneous and nonspecific, often mimicking malignant tumors, which makes diagnosis difficult and frequently one of exclusion. Immunosuppressed patients, including liver transplant recipients, have increased risk and the disease should be considered when a solitary or atypical hepatic mass is detected.

The case discussed involves a female patient who underwent living-donor liver transplantation and biliodigestive anastomosis in 2018 for cirrhosis secondary to hepatitis B virus infection. She developed chronic biliary stenosis managed with periodic exchanges of percutaneous transhepatic biliary drain. In 2024, she presented with catheter displacement and peri-drain bile leakage. An abdominal computed tomography scan revealed a 150 mL hepatic collection compatible with abscess. Percutaneous drainage and antibiotics were started, but poor clinical and radiologic response raised suspicion for post-transplant lymphoproliferative disorder. A guided liver biopsy ultimately identified Actinomyces sp., confirming hepatic actinomycosis. Treatment with intravenous ampicillin for 1 month led to major improvement and 90% lesion resolution. She was discharged on oral amoxicillin-clavulanate for additional 3 months, with outpatient follow-up demonstrating favorable clinical response.

Although uncommon, hepatic actinomycosis should be considered a possible cause of hepatic masses in liver transplant recipients. Management is mainly conservative with prolonged antibiotics and drainage may be used for refractory cases. Prognosis is generally positive when the condition is adequately treated.