An unusual case of Bence Jones myeloma with extremely low levels of monoclonal immunoglobulin.

This report describes the case of a 64-year-old woman with painful symptoms of the mandible produced by a lesion diagnosed as Bence Jones myeloma (kappa type). A bone survey revealed osteolytic lesions in the mandible, cranial bones, and humerus. Urinalysis showed no abnormality regarding the presence of monoclonal immunoglobulin fragments. Serum analysis by electrophoresis and immunoelectrophoresis did not demonstrate the presence of monoclonal immunoglobulin. However, the latter procedure disclosed a precipitation line formed by concentrated urine against anti-kappa serum. Microscopic examination of a mandibular specimen revealed numerous atypical plasma cells. Immunoperoxidase studies demonstrated kappa-chains localized within the rough endoplasmic reticulum, perinuclear region, and Golgi apparatus of the myeloma cells. The pathogenetic mechanism of the condition in this case, as well as its relation to Bence Jones myeloma and nonsecretory myeloma, is discussed.