Concurrent light chain amyloidosis and proximal tubulopathy: Insights into different aggregation behavior-A case report.

Due to differences in the protein folding mechanisms, it is exceedingly rare for amyloid light chain (AL) amyloidosis and monoclonal gammopathy of renal significance (MGRS) to coexist. We herein report the first case of concurrent AL amyloidosis and a subclass of MGRS, light chain proximal tubulopathy (LCPT). The 53-year-old female was diagnosed with smoldering myeloma immunoglobulin G kappa and AL amyloidosis with deposits in fat and gastrointestinal tissue. The kidney biopsy did not show amyloid deposits but electron microscopy revealed the presence of LCPT with crystal formation in proximal tubular epithelial cells. This case illustrates the complex pathophysiology of protein deposition in monoclonal gammopathies.