A Suspicious Hilar Mass Revealing an Uncommon Diagnosis of Pulmonary Actinomycosis in an Immunocompromised Young Female Patient: A Case Report and Literature Review

Actinomycosis is a chronic inflammatory infectious disease that can affect various organ systems. Pulmonary actinomycosis is an exceptionally uncommon clinical occurrence that yet deserves special attention, as it closely mimics a broad spectrum of infectious and neoplastic lung pathologies. The non-specific nature of its clinical features and radiological appearances makes early diagnosis quite challenging. The authors reported a 25-year-female with poorly controlled diabetes mellitus and morbid obesity who presented with a one-week history of unilateral, right-sided, pleuritic chest pain and shortness of breath. Chest imaging revealed a suspicious right hilar soft tissue mass encasing the right upper lobe bronchus with post-obstructive atelectasis. Transbronchial biopsy revealed suppurative granulomatous inflammation, and anaerobic cultures from the bronchial tissues grew Actinomyces species that were identified using the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) technique. A long course of penicillin-based antibiotics was employed, and follow-up imaging revealed a satisfactory response to the antimicrobial therapy. This case demonstrates that microbiological examination is imperative to accurately diagnose the etiology of suspicious lung masses in young immunocompromised hosts. It also proves the diagnostic value of the MALDI-TOF technique in the early identification of Actinomyces species.