Focal Light Chain Proximal Tubulopathy Complicated by Monoclonal Gammopathy of Undetermined Significance/Smoldering Multiple Myeloma Successfully Diagnosed by Immunofluorescence on Pronase-Digested Paraffin Section: Reports of Two Cases and Review of the Literature.

Light chain proximal tubulopathy (LCPT) is a rare type of paraprotein-related disease (PRDs) characterized by monoclonal free light chain (FLC) deposition in proximal tubular epithelial cells (PTECs). A diagnosis of LCPT requires identification of FLC deposition in PTECs; however, FLC luminescence defects in immunofluorescence staining using frozen tissue (IF-F), regarded as "masked LCPT", are occasionally encountered. We describe two cases of focal masked LCPT in monoclonal gammopathy of undetermined significance (MGUS) or smoldering multiple myeloma (SMM) diagnosed by IF in formalin-fixed, paraffin-embedded tissue sections following pronase digestion (IF-P) rather than by IF-F.

Lupus-like membranous nephropathy during the postpartum period expressing glomerular antigens exostosin 1/exostosin 2 and phospholipase A2 receptor: a case report.

Recently, several target antigens of membranous nephropathy (MN), such as phospholipase A2 receptor (PLA2R) and exostosin 1/exostosin 2 (EXT1/2), have been discovered. A 30-year-old woman was referred to our hospital with nephrotic range proteinuria and microscopic hematuria. She was first noted to have proteinuria before pregnancy, and her proteinuria worsened in the postpartum period.