Rare presentation of kappa light chain proximal tubulopathy with fibrillar aggregates

Introduction/Objective Patients with dysproteinemias may show a spectrum of renal alterations due to organized deposits of excess immunoglobulins, including primary amyloidosis, myeloma cast nephropathy, monoclonal immunoglobulin deposition disease, and light chain proximal tubulopathy (LCPT). Among the least common is LCPT, which shows ultrastructural cytoplasmic light chain inclusions with crystalline morphology or rarely fibrillar aggregates. We present the case of a patient with LCPT with fibrillar aggregates that is the only such case registered in our large academic surgical pathology electronic database. Our aim is to increase understanding and recognition of this rare variant. Methods/Case Report A 73-year-old man presented with 540 mg/day proteinuria, serum creatinine 5.73 mg/dL, platelets 178,000/cc, and 20% plasma cells in his bone marrow biopsy specimen. Kidney needle biopsy cores examined by light, fluorescent and transmission electron microscopy (EM) showed kappa light chain cast nephropathy and kappa LCPT with fibrillary aggregates, the latter requiring unmasking of kappa epitopes using pronase-treated paraffin sections. Congo red stain was negative. By EM, proximal tubules contained intracellular bundles of tightly aggregated fibrils with mean fibril diameter of 7.7 +/- 1.6 nm. Individual bundles were variably shaped as round, oval, spicular or irregular blobs. Fibrils were not seen in glomeruli. Results (if a Case Study enter NA) NA Conclusion This rare presentation of LCPT with fibrillar aggregates reinforces the utility of renal biopsy diagnosis that includes careful ultrastructural examination of renal tubules. In the absence of EM, the unique fibrillar organization of these cytoplasmic light chain aggregates would otherwise go unrecognized.

Coincidental light chain induced proximal tubulopathy with lupus nephritis: a case report and review of the literature

Background We report a case of light chain proximal tubulopathy associated with lupus nephritis in a patient known to have systemic lupus erythematosus. The kidney can be injured in several ways in any of these disorders. Light chain proximal tubulopathy is a rare form of renal tubular injury that may occur in and complicate plasma cell dyscrasia, characterized by cytoplasmic inclusions of the monoclonal light chain within proximal tubular cells. Lupus nephritis is a common form of renal injury as it occurs in about 25–50% of adult patients with systemic lupus erythematosus. Case presentation We present a 57-year-old African patient known to have systemic lupus erythematosus and hypertension presented with a new complaint of microscopic hematuria. A renal biopsy was performed and revealed lupus nephritis class II concurrently associated with light chain induced proximal tubulopathy. A subsequent bone marrow biopsy was performed, which revealed multiple myeloma. Conclusions We report a case of coincidental lupus nephritis and proximal tubulopathy featuring a combined constellation of rare histopathological features that might add to the relationship between systemic lupus and paraproteinemia.

C3 glomerulonephritis along with light chain proximal tubulopathy without crystal deposits in multiple myeloma: a case report

Background Multiple myeloma causes different types of renal injury. C3 glomerulonephritis (C3GN) is characterised by an abnormal deposition of complement C3 in the glomeruli due to abnormal activation of the alternative pathway of the complement system. While the association between C3GN and multiple myeloma has been well established, mild renal injury by C3GN in multiple myeloma patients with high levels of light chain has not been reported. Case presentation A 55-year-old Chinese man presented with proteinuria. Combined with immunofixation electrophoresis, bone marrow biopsy, and renal biopsy, he was diagnosed with IgA-type multiple myeloma accompanied by C3GN and light chain proximal tubulopathy without crystal deposits. Although he had a higher level of lambda serum-free light chain, the renal injury in this patient was mild. After treatment with four courses of BD, one course of PAD, and autologous stem cell transplantation, he achieved a very good partial hematologic response with stable renal function. Conclusions In multiple myeloma, the light chain reaches a certain level and persists, resulting in C3GN renal impairment. Early diagnosis and early intensive treatment are critical for the prognosis of such patients.

A case of diagnosis of light chain proximal tubulopathy in a kidney transplant patient

Light chain proximal tubulopathy (LCPT) is a disease characterised by accumulation of monoclonal immunoglobulins produced by tumour clones of plasma cells or B-lymphocytes in the epithelium of proximal renal tubules. One of LCPT forms is the crystal one, against the background of which epithelium of proximal renal tubules accumulates crystal structures of different sizes and shapes. This work presents an observation of a kidney transplant patient with crystal LCPT. The patient was admitted with azotaemia and underwent renal biopsy in order to establish the diagnosis. Morphological analysis drew attention to necrosis of epithelium of proximal renal tubules. Electron microscopy visualised crystal structures, immunohistochemical analysis of which revealed their monotypy in relation to lambda light chains of immunoglobulins. LCPT was diagnosed based on the comparison of the morphological picture and clinical data.