Pulmonary Actinomycosis: A Hidden Threat with Clinical Impact

Background: Pulmonary actinomycosis is a rare chronic infection that frequently mimics lung malignancy, often leading to delayed diagnosis due to its non-specific clinical and radiological presentation. Given the diagnostic challenges associated with this condition, the aim of this study was to evaluate the clinical presentation, diagnostic pathways, treatment strategies, and outcomes of patients diagnosed with pulmonary actinomycosis in a single center. Methods: We retrospectively reviewed patients diagnosed with pulmonary actinomycosis at our institution between January 2014 and December 2022. Diagnosis was established based on compatible clinical and radiological findings together with microbiological identification of Actinomyces by culture or polymerase chain reaction. Results: Twenty-two patients were included in the final analysis. The median age was 61.5 years and males were more frequently affected (59%). The median time from initial hospitalization to definitive diagnosis was 70 days. Actinomyces odontolyticus was the most frequently identified species. All patients received antibiotic therapy, with a median treatment duration of 45.5 days. Thirteen patients underwent surgical intervention, performed either for diagnostic purposes or for treatment of complications. Complete disease eradication through surgical management was achieved in six cases. During follow-up (median 24 months), overall survival at three years was 78%, with one death directly related to pulmonary actinomycosis. Conclusions: Pulmonary actinomycosis remains a diagnostic challenge due to its non-specific clinical presentation and low microbiological yield. Early clinical suspicion and a combined diagnostic approach including bronchoscopy and microbiological testing are essential for timely diagnosis. Surgical intervention may play an important diagnostic and therapeutic role in selected patients.