Multiple myeloma (light chain disease) with rheumatoid-like amyloid arthropathy and mu-heavy chain fragment in the serum.

A 52 year old man presented with multiple myeloma and widespread amyloidosis involving joints, bursae- carpal tunnels, lymph nodes and subcutaneous tissue. Osteolytic bone lesions and pathologic fracture of the neck of the left femur were found. Bone marrow was infiltrated with both plasmacytes and lymphocytes. The majority of plasma cells contained large cytoplasmic vacuoles. Free kappa II type light chains and mu-heavy chain fragment were detected in the serum, and kappa II type Bence Jones protein was found in the urine. The molecular weight of the mu-heavy chain fragment was found to be approximately 50,000 daltons. An immunofluorescence study, using the double labelling technic, showed that the majority of plasmacytes in bone marrow contained both mu and kappa antigenic determinants in the cytoplasm. A review of the 12 previously described patients with mu-heavy chain fragment in the serum showed a variable clinical picture, thus their natural history and therapeutic response are difficult to evaluate at the present time. It seems that mu-heavy chain fragment can be found in a variety of clinical conditions and that mu-heavy chain disease cannot yet be accepted as a separate clinical entity.