Curious case of the unexplained exudative pleural effusion.

We report a case of a 74-year-old male patient who was referred to the respiratory clinic with an incidental finding of a left sided pleural effusion. He was initially being treated by the general practitioner for chest infection with productive cough that had limited resolution after course of oral antibiotics. At the pleural clinic, 1.5 L of serosanguineous fluid was drained and sent for diagnostics. However, the diagnosis only reached as far as idiopathic exudative effusion with lymphocytes and plasma cells. He was then referred for video-assisted thoracoscopic surgery pleural biopsy and pleurodesis. It revealed black pleura with abundant IgG4 positive cells. He is followed up in respiratory clinic where further discussion and treatment has commenced.