[Light chain diseases--pathogenetic forms, diagnostic criteria. A suggestion for classification]

The clinical significance of the BJ-protein is quite variable: from an asymptomatic course of the light chain proteinuria for a long period of time to specific tissue deposits with serious organ damages and dysfunction. On the basis of literature data a classification of the light chain diseases is proposed: 1. Essential (bening) BJ-proteinuria; 2. Smoldering BJ-myeloma; 3. Light chain disease--BJ myeloma; 4. Light (and heavy) chain deposition disease: LC granular thick deposits mostly k type on electron microscopy, belonging to the constant region of the polypeptide chain and actively reacting with antiserums, not possessing tincturial properties; 5. LC cast nephropathy--LC coprecipitates in the tubular system; 6. LC crystaline deposition disease--specific crystaloid structures (in the Fanconi syndrome and experimental nephropathies); 7. AL-amyloidosis: LC precursor mostly lambda type from the variable region with specific fibrilar structure and typical tincturial properties. The suggested classification would resolve the diagnostic difficulties and determine the correct therapeutic management.