Light chain proximal tubulopathy with cast nephropathy in a case of multiple myeloma

The renal diseases most frequently associated with myeloma include cast nephropathy (CN), amyloidosis and monoclonal immunoglobulin deposition disease. Light chain proximal tubulopathy (LCPT) is reported less frequently. Majority of the cases with κ-restriction present with Fanconi syndrome (FS) and show crystals in proximal tubular epithelial cytoplasm. In contrast, those with λ-restriction are infrequently associated with FS and show cytoplasmic vacuolations in proximal tubular epithelial cytoplasm. Combination of morphologies in kidney affected by plasma cell dyscrasias is rare and co-existence of LCPT and CN is one of the rarest. We report a case of multiple myeloma having this rare combination of morphologies.