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Screening and Differential Diagnosis of Renal Light Chain-Associated Diseases

Background: Renal involvement in the light chain-associated diseases multiple myeloma (MM), amyloidosis (AL) and monoclonal immune position disease (MIDD) is common and differential diagnosis usually requires renal biopsy. The aim of this study was to investigate if noninvasive methods are viable to identify and differentiate between the various types of kidney diseases. Patients and Methods: All patients with a light chain-associated disease admitted to our center from 1996 to 2008 were retrospectively evaluated. Renal biopsy data were correlated with proteinuria findings. Results: Only the ratio of free ĸ/λ light chains showed a good sensitivity for myeloma cast nephropathy (MCN), AL and MIDD. The λ light chain was characteristic for AL, the ĸ light chain dominated in MIDD. Renal function at the time of diagnosis was worst in MIDD. MCN presented with a proteinuria of >3.5 g/g creatinine. In contrast, a higher proteinuria was found in AL or MIDD. Whereas the ĸ/λ ratio in the urine was pathological for all three diseases, extremely high or low ratios indicated the presence of MCN. However, in AL or MIDD, the ratio was only moderately elevated. Conclusion: A noninvasive differentiation between MCN and other forms of renal light chain disease is possible.