[Non-secreting myeloma. Case report with immunohistologic and electron microscopic studies].

Immunological, immunofluorescence and electromicroscopic studies were performed in a case of atypical myeloma. The 77-year-old patient presented with skeletal pain, multiple osteolytic lesions and bone marrow infiltration by atypical plasma cells. Monoclonal light chains kappa were confined to the plasma cells, as shown by immunofluorescence. No monoclonal immunoglobulin or fragments were detected in plasma or concentrated urine, even by highly sensitive immunological methods. The concentration of the immunoglobulins G, A and M in the plasma was markedly reduced. The plasma cells contained very little sarcoplasmatic reticulum. The simultaneous occurrence of monoclonal light chains kappa in the plasma cells and the absence of monoclonal immunoglobulins or fragments in plasma and urine suggest a non-secretory myeloma.