Myelomatous pleural effusion in a cat diagnosed with multiple myeloma.

Case Summary: A 10-year-old male castrated domestic shorthair cat was presented with a 3-day history of dyspnoea, chronic lethargy and inappetence. A bilateral pleural effusion was identified by thoracic ultrasound, and cytological examination revealed numerous atypical plasma cells. Biochemistry and serum protein electrophoresis revealed a severe hyperglobulinaemia associated with a monoclonal gammopathy.