JPC: A 63-year-old Caucasian man was seen in clinic having been referred by his general practitioner with a 10 -week history of progressive exertional dyspnoea, associated with dry cough and retrosternal discomfort over the preceding fortnight. There was no history of fever, weight loss, anorexia, haemoptysis, dysphagia or other localising systemic symptoms. His past medical history included psoriatic arthropathy, atrial fibrillation, hypertension and gastro-oesophageal reflux; of note, there was no recent history of palpitations or worsening peripheral oedema, while his joint disease remained quiescent. Current medications (all long-standing) included methotrexate, omeprazole, bisoprolol, aspirin, ramipril and simvastatin. He was a lifelong non-smoker and retired solicitor with no occupational risk factors for lung disease.

On examination he was afebrile with no palpable lymphadenopathy or clubbing. Cardiovascular examination demonstrated rate-controlled atrial fibrillation only; abdominal examination was normal. Respiratory examination revealed dull percussion note and reduced breath sounds at the right lung base, with normal resting oxygen saturations. Chest radiograph and thoracic ultrasound confirmed the presence of a large right-sided pleural effusion. Routine bloods including full blood count, clotting studies, renal function, liver function and serum calcium were unremarkable. I performed a diagnostic and therapeutic pleural aspiration, draining 1500 mL of straw-coloured fluid with no complications. Laboratory analysis showed the effusion to be an exudate (protein 46 g/L, lactate dehydrogenase (LDH) 961 IU/L, glucose 0.4 mmol/L); pleural fluid culture and cytology (including flow cytometry) were negative.

NMR: The presence of a cytology-negative exudative pleural effusion of unknown aetiology in a previously well individual requires urgent further investigation. The low pleural fluid glucose and high LDH may imply infection, although these findings are non-specific and can also be seen in the context of chronic inflammation or malignancy; furthermore, the clinical history and negative culture go against an infective cause. The presence of an inflammatory arthropathy may prompt consideration …