Organizing Pneumonia Secondary to Pulmonary Actinomycosis: A Case Report and Literature Review

Pulmonary actinomycosis is a common clinical infection caused by Actinomyces species. Although its treatment is very effective with Intravenous (IV) antibiotics, its diagnosis is challenging and easily missed. Organizing Pneumonia (OP) can be cryptogenic or secondary to different clinical diseases. Herein, we discuss a case of acute hypoxemic respiratory failure that was found to be due to OP, secondary to pulmonary actinomycosis, with a brief review of the literature. A 64-year-old male presented with acute hypoxemic respiratory failure two days after undergoing elective right total hip arthroplasty. Chest imaging with CT scan showed symmetric bilateral ground-glass opacities most pronounced within the upper lung lobes. The patient was treated initially with IV diuresis, steroids, and broad-spectrum antibiotics. However, his clinical status continued to worsen and his chest imaging showed worsening lung opacities. Video-assisted thoracoscopic lung biopsy (VATS) was done, and pathology results showed features of organizing pneumonia. Tissue culture confirmed Actinomyces species. The patient had clinical improvement after treatment with IV methylprednisolone and IV penicillin G. Pulmonary actinomycosis is very rarely associated with OP but this bacterial infection should always be in the differential diagnosis when OP is confirmed as the treatment is effective with IV antibiotics.