Actinomycosis is an uncommon infection caused by a group of anaerobic, Gram-positive organisms. Comprising approximately 15% of disease, pulmonary actinomycosis is typically marked radiographically by consolidation, often with cavitation and contiguous tissue spread (1). We report a case of pleural effusion as the sole radiographic manifestation of actinomycosis.
A 55 year-old man with a history of diabetes and coronary artery disease with CABG presented with two weeks of chest pain, shortness of breath, and low-grade fevers. His primary care physician had started azithromycin five days prior to admission. After a negative cardiac evaluation including catheterization, he was referred to the pulmonary service. The patient had moved from Sri Lanka decades earlier and worked as an auto-mechanic. He was a life-long non-smoker, and denied alcohol or illicit drug abuse. He denied changes in weight, chills, sweats, headaches, recent dental work, travel, or exposure to tuberculosis. On physical examination, he was febrile to 38.2 C, pulse 72, blood pressure 146/78, respiratory rate 16, and oxygen saturation of 97% on room air. He was a thin male in no acute distress. No cervical or axillary lymphadenopathy was noted; dentition was intact. Chest exam revealed decreased sounds on the right with dullness to percussion. Heart, abdominal, extremity, and skin exams were benign. Laboratory findings were remarkable for a WBC count of 21,000 x103/L and glucose of 230 mg/dL. Chest radiograph demonstrated a loculated right pleural effusion which was confirmed on chest CT scan (Graphic 1). Of note, the CT did not demonstrate significant adenopathy, pulmonary masses, or infiltrates. Sputum culture revealed normal respiratory flora and stained AFB negative. The patient was taken to the operating room for right thoracotomy with decortication revealing a gelatinous inflammatory exudate in the pleural space. While operative fluid and tissue cultures were negative, pathological specimen revealed severe acute and organizing pleuritits with organisms morphologically consistent with actinomycosis (Graphic 2). Postoperatively, the patient’s fever, chest pain, and dyspnea resolved; he received a two-week course of intravenous antibiotics and completed an out-patient oral course.
Pulmonary actinomycosis is often an indolent infection presenting classically in men during the fifth and sixth decades of life. Infection is more commonly seen in diabetics, immunocompromised, and those with pre-existing lung disease or poor dentition. Presumed routes of infection include aspiration, direct cervicofacial or abdominal extension, and hematogenous dissemination. Symptoms including fever and productive cough may raise concern for malignancy or other sub-acute infections including tuberculosis, fungal infections, or nocardia (1). While this case demonstrates many classic features of pulmonary actinomycosis, the radiographic presentation was atypical. As in this case, actinomycosis is often not included in the initial differential diagnosis for chest pain or pleural effusion. In fact, a broadened differential diagnosis was entertained only after a negative cardiac catheterization. As for many patients, thoracotomy was required for diagnosis; moreover, culture is often negative, mandating histological diagnosis. The classic sulfur-granule–a tangled mass of filamentous organisms–here demonstrated (Graphic 2), is not always seen. Classic radiographic characteristics include lower lobe consolidation with air-bronchograms or cavitation; associated pleural involvement including effusions, empyema, and thickening may be seen. Chest wall invasion with rib destruction is commonly described (2). This patient’s radiographic presentation, a loculated effusion without pulmonary infiltrates, cavitation, or adenopathy, is uncommon.
Pulmonary actinomycosis is a rare infection typically characterized by pleural involvement with simultaneous parachymal findings. This case demonstrates that pleural effusion may be the sole radiographic presentation of the disease.
Michael Bernstein, No Financial Disclosure Information; No Product/Research Disclosure Information