A 77-year-old-man was admitted to our respiratory department for an organized, unilateral pleural effusion. He reported a severe former smoking habit (150 pack/years). He worked mainly as a tailor and, for some years, as a metalworker; he is currently retired, and he spends his time in his garden. His medical history demonstrated that he suffered from arterial hypertension, treated with 10 mg of Olmesartan once daily. He underwent partial gastrectomy some years before for a peptic ulcer. In the month before the admission, he reported a stroke, which led to slight dysarthria; because of this, he is currently on therapy of 300 mg Aspirin once daily. He denied any clinical history of ischaemic heart disease, heart failure, or diabetes. No apparent sources of asbestos exposure were known.
In the month of April 2018, he came to the emergency department of our hospital for acute dyspnoea and tachyarrhythmia (166 beats/min) with a normal arterial pressure (120/80 mmHg). He had a partial arterial oxygen pressure (PaO2) of 57 mmHg with normal partial arterial carbon dioxide pressure (PaCO2) and pH. The patient also complained of exertional dyspnoea from a few months. He denied fever, cough, and chest pain in the previous months. Blood tests showed macrocytic anaemia (haemoglobin 11 g/dL, mean cell volume 104 fL), a slight value of inflammatory response (leucocytes 10.5 x 109/L with 80% neutrophils, C-reactive protein 28.70 mg/L). The electrocardiograph showed a paroxysmal atrial fibrillation, which was treated with amiodarone and oral anticoagulation therapy. The chest X-ray showed a unilateral, organized pleural effusion (Fig. 1). A chest CT scan showed a right, organized pleural effusion and a thickening of the right parietal and mediastinal pleura, suggestive of malignant pleural disease, without mediastinal lymph node involvement but with a compressive atelectasis of the adjacent lung parenchyma (Fig. 1).
On the suspicion of pleural mesothelioma or a pleural localization of a lymphoproliferative disease, the patient underwent medical thoracoscopy, in which multiple biopsies were performed and a pleural drainage was performed, with a removal of 850 mL of pleural fluid. Physical examination of the pleural fluid showed a corpusculated, orange-coloured liquid with many cords of fibrin; chemical analysis showed an acid pH (7.18) and lactate 9.9 mmol/L, with pleural fluid lactate dehydrogenase (LDH) of 7849 IU/L and total proteins of 5.7 g/dL. Light's criteria were positive for an exudative pleural effusion. Cytology showed a relevant inflammatory pattern, mainly composed of neutrophils (60.9% of total) and lymphocytes (36.5% of total); no neoplastic cells were described. The research of mycobacteria tuberculosis through in vitro culture was negative. A peripheral lymphocyte subset typing method by cytofluorometry excluded lymphoid malignancies.
Histological exam performed on biopsies and pleural fluid showed a "purulent pleuritis" with evidence of Bacillus megaterium infection, which was sensible to all antibiotics tested, except for clindamycin. Therapy with meropenem of 3 g/day and levofloxacin of 500 mg/day was started, with benefits. A chest CT scan after two weeks of the antibiotic therapy showed a significant improvement (Fig. 2) with normality of blood exams. The patient was no longer dyspnoeic, without a need for oxygen. The patient achieved completed resolution.