1 | INTRODUCTION
Actinomycosis is a chronic granulomatous infection caused by the gram-positive anaerobic bacteria actinomyces, which form long branching filaments that resemble the hyphae of fungi [1, 2]. Actinomyces is a part of the normal flora that colonizes the mouth in humans [1, 2]. According to the site of involvement, actinomycosis infection is classified into the following clinical forms: cervicofacial disease, which is the most common, followed by abdominopelvic and pulmonary. The pulmonary form of actinomycosis accounts only for around 15% of all cases [2]. The incidence is higher in men in their fourth and fifth decades (with male/female ratio being ≥ 3:1), and smokers with poor dental hygiene are at increased risk [3]. The clinical and radiological findings of pulmonary actinomycosis may mimic pneumonia, tuberculosis, and malignancy, resulting in misdiagnosis and delay in treatment [1, 2]. In this article, we report a rare case of pulmonary actinomycosis in a patient with COPD associated with an unusual clinical presentation of pleural effusion.