Trimolecular Complexes of Light Chain Dimers in Serum of a Patient with Multiple Myeloma

Background: Patients with multiple myeloma often have Bence Jones proteins composed of free monoclonal light chains of the or type in their urine. Usually, these light chains exist as monomeric or dimeric forms, but rarely, larger molecules, such as tetramers, have been reported in the serum. Methods and Results: We report the presence of trim-eric complexes of light chain dimers in a patient who was diagnosed with a free light chain multiple my-eloma 2 years earlier and subsequently underwent a stem cell transplant. Recently, the patient presented with a large serum M-spike (23 g/L) by protein electro-phoresis. The spike consisted of monoclonal light chains without a heavy chain. The urine contained only 8 mg of light chain in a 24-h specimen. Quantitativ