Kidney Function

Light chain tubulopathy is a rare complication associated with plasma cell dyscrasias. There are no more than 80 cases reported in the English literature; the defining series was 17 patients described by Maldonado et al in 1975. That original work showed in patients with acquired Fanconi syndrome an association with monoclonal immunoglobulin light chain proteinuria, slow progression of the plasma cell dyscrasia, and crystal formation in proximal tubule cells. Since that time, a variety of clinical and pathologic findings have been reported with respect to light chain tubulopathy. Messiaen et al reported a series of 11 cases, 3 of which had no crystal formation, 2 had only partial Fanconi syndrome, and the degree of plasma cell dyscrasia ranged from monoclonal gammopathy of undetermined significance (MGUS) to full-blown multiple myeloma. The timing of kidney manifestations in relation to the diagnosis of plasma cell dyscrasia also varies. Most reports show that the investigation of proteinuria, kidney failure, Fanconi syndrome, or osteomalacia leads to the discovery of plasma cell dyscrasia; however, there are instances in which light chain tubulopathy proceeded the diagnosis of plasma cell dyscrasia. Additionally, light chain tubulopathy rarely occurs without Fanconi syndrome, as was described recently in 1 case report. We report a case of light chain tubulopathy without Fanconi syndrome found to have significant crystalline inclusions in tubular epithelial cells and podocytes discovered many years after the diagnosis of MGUS.