Pleural amyloidosis: timely unmasking of apple-green birefringence in pleural biopsy.

8%-25% of cases of pleural effusion remain undiagnosed after routine workup. Some of the causes for pleural effusion are less often considered as a differential diagnosis owing to their rarity. While not all require a pleural biopsy, it remains a valuable tool for the definitive diagnosis of uncommon pleural effusions and guides treatment decisions. This case exemplifies the value of timely intervention in uncovering an unconventional form of pleural amyloidosis. An elderly male presenting with right-sided pleural effusion. The patient underwent timely medical thoracoscopy and was subsequently diagnosed with AL amyloidosis. Following therapy, the patient demonstrated marked clinical improvement, with radiographic resolution of the effusion and a favourable haematologic response.