Pleural effusion--presenting sign in multiple myeloma.

A patient with multiple myeloma in whom recurrent right pleural effusion was the presenting sign of the disease is reported. An IgA (k) monoclonal component was found in both the pleural effusion and the serum. The bone marrow specimen was interpreted as typical for multiple myeloma and the pleural fluid contained numerous plasma cells. Treatment with cyclophosphamide was followed by clinical improvement and the disappearance of the pleural effusion.