A case of pleural and pericardium amyloidosis with effusion associated with multiple myeloma relapse.

An 80-year-old man with a history of Bence-Jones potein (BJP) λ-type multiple myeloma (MM), which had been in remission for 16 years, was examined for shortness of breath and was found to have bilateral pleural and pericardial effusions. A pleural fluid test and a pleural biopsy under local anaesthesia performed by a previous physician failed to make the diagnosis. Despite diuretic therapy, his condition necessitated frequent thoracentesis. The patient was referred to our hospital and thoracoscopic pleural and pericardial biopsies performed under general anaesthesia revealed λ-type AL amyloidosis, indicating a relapse of MM. Despite drug therapy for MM, the patient died from aspiration pneumonia. The case underscores the importance of considering amyloidosis in differential diagnoses for refractory effusions, especially in patients with a history of MM, even after long-term remission.