A 47-year old man with a past medical history of depression, chronic fatigue syndrome and gastro-oesophageal reflux disease presented to the Emergency Department with a four-week history of dry cough, abdominal pain and weight loss. Regular medications included omeprazole and mirtazapine, and he had no known drug allergies. The patient was a non-smoker and had a history of high alcohol consumption. He previously worked in an office but was unemployed at the time. There was no history of foreign travel. On examination he was cachectic and febrile (37.9  C), with a heart rate of 119bpm and blood pressure of 110/85 mmHg. His saturations were 98% on room air, and chest examination revealed reduced breath sounds on the left consistent with a pleural effusion. The rest of the examination was unremarkable.
Blood tests showed raised inflammatory markers and deranged liver function tests (Fig. 1). A HIV test was negative. Chest radiograph revealed bilateral effusions, larger on the left with patchy shadowing in both lung fields (Fig. 2). Pleural ultrasound demonstrated a large free flowing anechoic pleural effusion.
A chest drain was inserted. Analysis of the heavily blood stained fluid showed a pH of 7.44, LDH 4557U/L, protein level of 41g/L and no malignant cells on cytology. Initial gram stain was negative and no Acid Fast Bacilli were seen. Three sputum samples were also negative for Acid Fast Bacilli.
CT scan of the chest, abdomen and pelvis (Fig. 3) showed multiple nodules throughout the lungs, small mediastinal lymph nodes and pleural thickening within the left hemi-thorax extending onto the mediastinal surface. There were no abnormalities in the abdomen or pelvis. The radiological appearances were reported as favouring a diagnosis of malignancy rather than infection.
The most likely diagnosis was thought to be disseminated malignancy with unknown primary with super imposed pulmonary infection.
The patient became increasingly hypoxic despite treatment with broad-spectrum antibiotics. In the absence of a definitive diagnosis of malignancy, he was intubated for ventilatory support. A broncho-alveolar lavage obtained from bronchoscopy showed no malignant cells, but microbiological analysis yield numerous Acid Fast Bacilli. A diagnosis of miliary tuberculosis was made and standard Tuberculosis treatment (pyranzinamide, rifampicin, isoniazid, and ethambutol) was initiated. The patient made good clinical improvement and was eventually discharged.
Ten weeks after his bronchoscopy, an organism resistant to pyranzinamide was cultured and identified as Mycobacterium Bovis (M. Bovis). This unexpected finding led to a review of the history. The patient had not travelled abroad or consumed any unpasteurised milk. He owned a healthy cat and had lived next to a dairy farm for many years. His wife recalled that there might have been cases of Bovine Tuberculosis among the cattle on the farm. The Department of Public Health was informed and the patient's cat was tested for M. Bovis which subsequently was negative. Pyrazinamide was stopped and the patient completed a nine-month treatment (rifampicin, isoniazid and ethambutol) for pulmonary M. Bovis and made a gradual recovery.