During a 40 month interval, 35 patients were seen with a plasma cell dyscrasia in which the only detectable monoclonal immunoglobulin abnormality consisted of excess production of either type kappa or type lambda light chains (Bence Jones protein). This group constituted 17.3 per cent of the total number of patients with plasma cell dyscrasias and 25.7 per cent of the patients with myeloma identified during the same period. Variable initial clinical presentation, the absence of a typical monoclonal serum spike and the unreliability of commonly used urine protein tests made recognition of the disorder difficult in many patients. Sulfosalicylic acid and p-toluene sulfonic acid proved valuable in screening for urine protein. Definition of "proteinuria" by quantitative, electrophoretic and immunochemical studies was essential for diagnosis. Bence Jones proteinemia was present in 80 per cent of the patients; panhypogammaglobulinemia and lytic bone lesions were demonstrable in more than 60 per cent. Although no specific morphologic abnormality of marrow plasma cells was evident by light microscopy, the absence of rouleau on peripheral blood smear was a helpful diagnostic clue. Although patients with lambda light chains presented with more Bence Jones proteinuria, this did not correlate with the severity of initial renal functional impairment or with survival when compared to patients with kappa light chains. No other clinical or laboratory observation differentiated the groups with kappa light chains from those with lambda light chains. Amyloid was identified in seven patients. Their course was dominated by the features of primary systemic amyloidosis instead of the usual findings of classic myeloma. Patients with amyloidosis had lower initial serum albumin levels, fewer lytic bone lesions and reduced survival compared to patients without amyloidosis.
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