Non‐Secretory or Low‐Secretory Myeloma with Intracellular Kappa Chains

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Abstract
In 6 cases of multiple myeloma characterized by no demonstrable monoclonal immunoglobulin [Ig] in plasma or urine or by trace amounts (.ltoreq. 0.1 g/l) of monoclonal .kappa.-chains in the urine, there was an ilfiltration of the bone marrow by plasma cells containing .kappa. chains but no H chains. A retrospective analysis was made of 126 consecutive cases of Bence Jones myeloma. The number of .kappa. and .lambda. cases was approximately the same. All cases secreting .ltoreq. 0.1 g L chains/l urine were of .kappa. type. This contrasts with a .kappa./.lambda. ratio of 1.4-1.9 among reported series of M-components containing H and L chains. A review of reported cases of non-secretory myeloma revealed a preserved capacity for Ig synthesis in most cases and among these a preponderance of .kappa. chain producing clones. These observations might be explained by a higher tendency for .kappa. chain producing cells to mutate to low secretors or to cells producing abnormal L chains which are catabolized rapidly. The clinical data from the patients do not indicate a more pessimistic prognosis in non- or low-secretory myeloma than in other cases of multiple myeloma.