INTRODUCTION: Actinomycosis is a chronic suppurative infection due to filamentous, gram-positive, nonspore-forming, anaerobic bacteria of the genus Actinomyces. Actinomyces species are commensals of the human oropharynx, gastrointestinal tract, and female genitalia. Involvement of the thorax accounts for fifteen to twenty percent of actinomycosis cases.
CASE PRESENTATION: A 62 year-old female, former smoker, was diagnosed with Stage IIIB squamous cell carcinoma of the lung in December of 2007. The patient had a covered nitinol endobronchial stent deployed within the right mainstem bronchus and bronchus intermedius due to extrinsic compression of these bronchi by the malignancy. The patient subsequently received weekly carboplatin and paclitaxel for eight weeks with concurrent external beam radiation therapy. The patient tolerated these treatment modalities without complication. Positron emission tomography (PET) CT completed 18 and 27 months after the conclusion of treatment showed no metabolic evidence of recurrent disease. Subsequently, at 33 months, the patient developed a productive cough associated with fatigue and weight loss. PET-CT revealed abnormal FDG hypermetabolism posteriorly and inferiorly to the distal portion of the stent suspicious for recurrent disease. A bronchoscopy showed concentric soft tissue at the distal portion of the stent causing 30% obstruction of the airway. Beyond this obstruction, the airways were patent without additional endobronchial lesions. Pathology from an endobronchial biopsy of this soft tissue was negative for malignancy but revealed chronic active bronchitis with filamentous microorganisms staining positive with Gomori methenamine silver consistent with actinomyces. The patient was diagnosed with endobronchial actinomycosis and was started on oral Penicillin VK. Additionally, rigid bronchoscopy was completed with removal of the covered nitinol stent. Repeat bronchoscopy eight weeks after the initiation of antimicrobial therapy and stent removal demonstrated complete patency of the airway orifices. Endobronchial biopsies were obtained. Pathology revealed unremarkable peribronchial tissue without evidence of malignancy or actinomyces. Anaerobic culture was negative for actinomyces. There has been complete resolution of symptoms. Penicillin VK will be continued for at least 12 weeks with plans for repeat PET-CT at 16 weeks.
DISCUSSION: Thoracic actinomycosis classically presents as an intra-pulmonary infection of the alveoli, peribronchial tissue, and/or bronchioles. Endobronchial actinomycosis is a rare condition which has been reported in association with aspiration of a foreign body or broncholithiasis. A critical component in the development of actinomycosis is the disruption of the mucosal barrier, thereby allowing invasion of the microorganisms from aspirated oropharnygeal secretions. In the present case, the covered nitinol endobronchial stent contributed to disruption of the mucosal barrier with the development of inflamed granulation tissue. Therefore, antimicrobial therapy with Penicillin VK alone would not be adequate to achieve complete resolution. The foreign body, the covered nitinol stent, must be removed so that the protective mucosal barrier can re-generate. To our knowledge, this is the first reported case of endobronchial actinomycosis associated with an endobronchial stent.
CONCLUSIONS: Endobronchial actinomycosis can be difficult to diagnose, particularly when it is not suspected. This case emphasizes the importance that pulmonologists must recognize actinomycosis as a potential cause of endobronchial disease in patients with endobronchial stents. Additionally, one must be cognizant that endobronchial actinomycosis can mimic bronchogenic carcinoma and cause FDG hypermetabolism on PET-CT.
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DISCLOSURE: The following authors have nothing to disclose: Amanda Godfrey, Javier Diaz-Mendoza, Cynthia Ray, Sajive Aleyas
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