Concurrent Crystalline Light-Chain Proximal Tubulopathy and Membranous Nephropathy: A Case Report and Literature Review.

Light-chain proximal tubulopathy (LCPT) is typically characterized by the intracytoplasmic deposition of light chains within the proximal tubular epithelial cells, which is usually classified into crystalline and noncrystalline subgroups. Membranous nephropathy (MN) is a common glomerular disease characterized by diffused subepithelial electron-dense deposits along the capillary loop accompanied by the effacement and microvillus transformation of the foot process. Here, we report a biopsy-confirmed case of a concurrence of LCPT with crystals (κ light chains restricted) and antigen-undetermined MN in a male patient. The patient presented with low-molecular-weight proteinuria, increased serum creatinine levels, and incomplete Fanconi syndrome. To our knowledge, this is the first report of a concurrence of LCPT and independent MN of unknown target antigens, which may enrich our recognition of monoclonal gammopathy of renal significance with synchronous MN.

Improvement of Light Chain Proximal Tubulopathy without Crystals in IgGλ-type Monoclonal Gammopathy of Undetermined Significance Using Bortezomib and Dexamethasone.

A 70-year-old woman with acute kidney injury, a high serum Creatinine (Cr) level (3.91 mg/dL), and proteinuria (protein/Cr ratio 1.59 g/gCr) was admitted. Serum IgG λ-type and urinary λ-type M proteins were observed. A bone marrow examination indicated monoclonal gammopathy of undetermined significance (MGUS). A renal biopsy showed distended proximal tubular cells, and immunofluorescence identified tissue positive for proximal tubular cell λ light chains. Electron microscopy identified fibril-like structures in the lysosomes. The patient was diagnosed with light chain proximal tubulopathy without crystals in IgG λ-type MGUS and treated with bortezomib and dexamethasone therapy, which improved her renal function.

Combined crystal-storing histiocytosis, light chain proximal tubulopathy, and light chain crystalline podocytopathy in a patient with multiple myeloma: a case report and literature review.

BACKGROUND: Crystal-storing histiocytosis (CSH), light chain proximal tubulopathy (LCPT), and light chain crystalline podocytopathy (LCCP) are rare complications of multiple myeloma (MM) or monoclonal gammopathy of renal significance, and their diagnoses are challenging. CASE PRESENTATION: In this case, a 69-year-old Chinese woman presented with suspicious Fanconi syndrome with renal insufficiency. Immunofixation electrophoresis of both serum and urine revealed elevated immunoglobulin G kappa (IgGkappa) and kappa light chain. Bone marrow aspirate revealed 15% plasma cells with considerable cytoplasmic granular inclusions and needle-shaped crystals. Renal biopsy confirmed the final pathologic diagnosis of kappa-restricted CSH, combined LCPT and LCCP by immunoelectron microscopy. A number of special casts were present which could easily be misdiagnosed as light chain cast nephropathy. Immunofluorescence on frozen tissue presented false negative for kappa light chain, as ultimately proven by paraffin-embedded tissue after pronase digestion. MM and CSH were diagnosed, and two cycles of chemotherapy were given. The patient subsequently refused further chemotherapy, and her renal function remained relatively stable during a 2.5-year follow-up period. CONCLUSIONS: In conclusion, we report a rare case of generalized kappa-restricted CSH involving bone marrow and kidney, combined with LCPT and LCCP, provide a comprehensive summary of renal CSH, and propose a new nomenclature of monoclonal immunoglobulin-induced crystalline nephrology. The presentation of monoclonal immunoglobulin and Fanconi syndrome should suggest the presence of monoclonal immunoglobulin-induced crystalline nephrology. Use of paraffin-embedded tissue after pronase digestion and immunoelectron microscopy is beneficial to improve the sensitivity of diagnosis.

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.

Clinic-pathological characteristics of rare tubulointerstitial diseases. / å°‘è§è‚¾å°ç®¡é—´è´¨æ€§ç–¾ç— çš„ä¸´åºŠåŠç— ç†ç‰¹å¾åˆ†æž.

OBJECTIVES: Tubulointerstitial diseases is one of the common causes of renal dysfunction. Some rare pathological types are easy to be misdiagnosed and missedly diagnosed because of their low prevalence and relatively insufficient understanding, which affects the treatment and prognosis of patients. This study aims to explore clinical manifestations and pathological characteristics of several rare tubulointerstitial diseases, and therefore to improve their diagnosis and treatment. METHODS: A total of 9 363 patients diagnosed by renal biopsy in the Department of Nephrology, Second Xiangya Hospital, Central South University from November 2011 to September 2021 were selected. Six cases of light chain cast nephropathy (LCCN), 2 cases of light chain proximal tubulopathy (LCPT), 1 case of LCCN with LCPT, 4 cases of genetic tubulointerstitial disease, and 6 cases of non-genetic related tubulointerstitial lesion were screened out, and their clinical manifestations and renal biopsy pathological results were collected, compared, and analyzed. RESULTS: Patients with LCCN presented with mild to moderate anemia, microscopic hematuria, and mild to moderate proteinuria. Compared with patients with LCPT, proteinuria and anemia were more prominent in patients with LCCN. Five patients with LCCN and 2 patients with LCPT had elevated serum free kappa light chain. Five patients with LCCN presented clinically with acute kidney injury (AKI). Two patients with LCPT and 1 patient with LCCN and LCPT showed CKD combined with AKI, and 1 LCPT patient presented with typical Fanconi syndrome (FS). Five patients with LCCN, 2 patients with LCPT, and 1 patient with LCCN and LCPT were diagnosed with multiple myeloma. Five patients with LCCN had kappa light chain restriction in tubules on immunofluorescence and a "fractured" protein casts with pale periodic acid-Schiff (PAS) staining on light microscopy. Immunohistochemical staining of 2 LCPT patients showed strongly positive kappa light chain staining in the proximal tubular epithelial cells. And monoclonal light chain crystals in crystalline LCPT and abnormal lysosomes and different morphological inclusion bodies in noncrystalline LCPT were observed under the electron microscope. Six patients with LCCN were mainly treated by chemotherapy. Renal function was deteriorated in 1 patient, was stable in 4 patients, and was improved in 1 patient. Two patients with LCPT improved their renal function after chemotherapy. Four patients with genetic tubulointerstitial disease were clinically presented as CKD, mostly mild proteinuria, with or without microscopic hematuria, and also presented with hyperuricemia, urine glucose under normal blood glucose, anemia, polycystic kidneys. Only 1 case had a clear family history, and the diagnosis was mainly based on renal pathological characteristics and genetic testing. Compared with patients with non-genetic related tubulointerstitial lesion, patients with genetic tubulointerstitial disease had an earlier age of onset, higher blood uric acid, lower Hb and estiated glomemlar fitration (eGFR), and less edema and hypertension. Renal pathology of genetic tubulointerstitial disease presented tubular atrophy and interstitial fibrosis, abnormal tubular dilation, glomerular capsuledilation, and glomerular capillary loop shrinkage. Glomerular dysplasia and varying degrees of glomerular sclerosis were observed. Genetic tubulointerstitial disease patients were mainly treated with enteral dialysis, hypouricemic and hypoglycemic treatment. Two genetic tubulointerstitial disease patients had significantly deteriorated renal function, and 2 patients had stable renal function. CONCLUSIONS: Patients with AKI or FS, who present serum immunofixation electrophoresis and/or serum free kappa light chain abnormalities, should be alert to LCCN or LCPT. Renal biopsy is a critical detection for diagnosis of LCCN and LCPT. Chemotherapy and stem cell transplantation could delay progression of renal function in patients with LCCN and LCPT. If the non-atrophic area of the renal interstitium presents glomerular capsule dilatation, glomerular capillary loop shrinkage, and abnormal tubular dilatation under the light microscopy, genetic tubulointerstitial disease might be considered, which should be traced to family history and can be diagnosed by genetic testing.

Morphometric Analysis of Lysosomes in the Renal Tubule in Monoclonal Gammopathy Using Transmission Electron Microscopy: "Mottled Appearance" and Beyond.

Lysosomal "mottled appearance", or uneven electron-dense content related to monoclonal gammopathy (MG), has been mainly described in light chain proximal tubulopathy (LCPT). We aimed to determine the ultrastructural characteristics of lysosomal mottled appearance in kidney biopsies and its association with LCPT and MG. Seventy-seven biopsies were grouped into LCPT (n = 5), MG conditions other than LCPT (n = 43), and non-MG conditions (n = 29). The mottled lysosomes in the renal tubules were evaluated using transmission electron microscopy and morphometric analysis. Mottled lysosomes were more prevalent (% of present cases) and frequent (no. of mottled lysosomes/20,000× ultramicroscopic field) in the LCPT group (100% and 8.20 ± 4.15/field) than in the MG (41.9% and 1.13 ± 2.05/field) and non-MG (37.9% and 0.80 ± 1.44/field) groups. In morphometric analysis of all mottled lysosomes (n = 520) detected from the 34 biopsies (5 LCPT, 18 MG, and 11 non-MG), we found that mottled lysosomes were larger, more irregular, and more electron-dense for the LCPT group than for the MG and non-MG groups. Therefore, mottled lysosomes can be present in disorders other than LCPT or even without MG. The morphological characteristics of mottled lysosomes could provide objective guidance for the diagnosis of LCPT.

[Renal involvement in monoclonal gammopathies]. / Compromiso renal en gammapatías monoclonales.

INTRODUCTION: The kidney is one of the organs most frequently affected by disease processes which produce monoclonal immunoglobins, therefore renal morphological and immunopathological alterations should be clearly recognized. OBJECTIVE: To describe the pathological features of renal involvement in monoclonal gammopathies. MATERIAL AND METHODS: A descriptive, retrospective and cross-sectional study of renal biopsies studied in a single center during a period of 14 years was carried out. RESULTS: 102 cases were included, of which 53% were male patients and the median age was 62.5 years (range 34 - 79). 97% of the biopsies were from native kidneys. The most frequent histopathological diagnosis (31.4%) was myeloma kidney, with kappa being the light chain most frequently deposited (65.6% of cases). AL amyloidosis was the second most common (29.4%) where the lambda chain predominated in 86.6%, followed by light chain deposition disease (20.6%) with the predominance of the kappa chain in 66.6%. CONCLUSIONS: The most frequent renal involvement due to monoclonal gammopathies was myeloma kidney with deposition of kappa light chains, followed by AL lambda amyloidosis; these diseases were found more frequently in patients over 50 years of age.

Compromiso renal en gammapatías monoclonales / Renal involvement in monoclonal gammopathies

Introducción: El riñón es uno de los órganos más comprometidos en enfermedades con producción de inmunoglobulinas monoclonales, por lo que es de gran importancia caracterizar muy bien las alteraciones morfológicas e inmunopatológicas en dicho compromiso. Objetivo: Describir las características del compromiso renal en gammapatías monoclonales desde una perspectiva anatomopatológica. Material y métodos: Se realizó un estudio descriptivo, retrospectivo y transversal, recolectándose biopsias renales estudiadas en un único centro durante un período de 14 años. Resultados: Se incluyeron 102 casos provenientes de 102 pacientes, el 53% de sexo masculino, la mediana de la edad fue 62,5 años (rango 34-79). El diagnóstico histopatológico más frecuente fue riñón de mieloma (31,4% de los casos), siendo kappa la cadena ligera más frecuentemente depositada (65,6% de casos), seguido de amiloidosis AL (29,4%), donde predominó la cadena lambda en un 86,6% y la enfermedad por depósitos de cadenas ligeras (20,6%) con predominio de la cadena kappa: 66,6%. El 97% de las biopsias fueron de riñón nativo. Conclusiones: El compromiso renal por gammapatías monoclonales más frecuente fue el riñón de mieloma con depósito de cadenas ligeras kappa, seguida de la amiloidosis AL lambda; estas enfermedades se encontraron con mayor frecuencia en pacientes mayores de 50 años de edad.(AU)

Introduction: The kidney is one of the organs most frequently affected by disease processes which produce monoclonal immunoglobins, therefore renal morphological and immunopathological alterations should be clearly recognized. Objective: To describe the pathological features of renal involvement in monoclonal gammopathies. Material and methods: A descriptive, retrospective and cross-sectional study of renal biopsies studied in a single center during a period of 14 years was carried out. Results: 102 cases were included, of which 53% were male patients and the median age was 62.5 years (range 34 - 79). 97% of the biopsies were from native kidneys. The most frequent histopathological diagnosis (31.4%) was myeloma kidney, with kappa being the light chain most frequently deposited (65.6% of cases). AL amyloidosis was the second most common (29.4%) where the lambda chain predominated in 86.6%, followed by light chain deposition disease (20.6%) with the predominance of the kappa chain in 66.6%. Conclusions: The most frequent renal involvement due to monoclonal gammopathies was myeloma kidney with deposition of kappa light chains, followed by AL lambda amyloidosis; these diseases were found more frequently in patients over 50 years of age.(AU)

Monoclonal Gammopathy of Renal Significance: Histomorphological Spectrum at a Tertiary Care Center.

Introduction: The term monoclonal gammopathy of renal significance (MGRS) has been described to include patients with renal manifestations associated with circulating monoclonal proteins with or without a clonal lymphoproliferation (B-cell or plasma cell) and not meeting diagnostic criteria for an overt hematological malignancy. A host of MGRS-associated lesions have been described that involve various renal compartments. Our study describes the histomorphological spectrum of MGRS cases at our center in the last 5 years and description as per the classification system of the International Kidney and Monoclonal Gammopathy Research Group (IKMG). Material and Methods: Retrospective analysis was carried out of all the renal biopsies with characteristic monoclonal immunoglobulin lesions for histopathological diagnosis between years 2015 and 2020 and reviewed by two independent pathologists. Results: Most patients in the study belonged to the fifth decade, with a median age of 50 years (mean 50.14 ± 10.43) range (24-68 years) with a male preponderance. Most patients presented with proteinuria as the sole manifestation (66.6%). Many of the patients (48%) had an M spike by serum protein electrophoresis or urinary protein electrophoresis with an abnormal serum free light chain assay (60.8%). AL amyloidosis was the most common diagnosis observed on histopathological evaluation (68.7%), followed by light chain deposition disease (10.4%). Conclusion: MGRS lesions are infrequently encountered in the practice of nephropathology and pose a diagnostic challenge due to the limitation of a congruent clinical or hematological picture. A thorough histological examination with immunofluorescence and electron microscopy often precipitates in the right diagnosis and prompts timely management.

Combined light chain crystalline tubulopathy, podocytopathy, and histiocytosis associated with Bence-Jones κ protein diagnosed via immuno-electron microscopy.

We herein report a case of a combined crystalline light chain tubulopathy, podocytopathy, histiocytosis, and cast nephropathy in a patient with monoclonal gammopathy of renal significance (MGRS). A 66-year-old female with impaired renal function was referred to our department. Despite intravenous fluid resuscitation, the kidney function worsened progressively; thus, a kidney biopsy was performed. The kidney biopsy revealed light chain proximal tubulopathy (LCPT) with crystals, light chain crystal podocytopathy (LCCP), crystal-storing histiocytosis (CSH), and light chain cast nephropathy (LCCN). Of note, LCCP and CSH were diagnosed via electron microscopy. Serum and urine immunoelectrophoresis (IEP) revealed the presence of monoclonal Bence-Jones protein and free κ light chains. Bone marrow aspiration showed < 10% plasma cell proliferation. Thus, we had encountered a rare case in which a variety of kidney lesions were combined with MGRS. Most of the LCPT, LCCP, and CSH cases show monoclonal IgG κ, while our case showed Bence-Jones protein κ.

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.

Clinicopathological characteristics of light chain proximal tubulopathy in Korean patients and the diagnostic usefulness of immunohistochemical staining for immunoglobulin light chain.

BACKGROUND: Light chain proximal tubulopathy (LCPT) is a rare paraproteinemic renal disease that has been mostly reported in Western patients. LCPT is characterized by the accumulation of immunoglobulin (Ig)-light chain (LC) in the proximal tubule. Immunohistochemical staining for Ig-LC has not been investigated in the context of LCPT. We reported the clinicopathological characteristics and Ig-LC immunoexpression of patients with LCPT for the first time in Korea. METHODS: We reviewed the clinicopathological findings of 5 Korean patients diagnosed with LCPT between 2016 and 2018. In addition, immunohistochemical staining for κ-LC and λ-LC was conducted on paraffin-embedded tissues. RESULTS: The median age was 63 years, and the male-to-female ratio was 3:2. The primary renal manifestations were either azotemia or tubular proteinuria. All patients were diagnosed with multiple myeloma with monoclonal κ-LC (#1-2) or λ-LC (#3-5) in the serum and urine. Kidney biopsies revealed diverse and subtle alterations of the proximal tubule, including crystallization, vacuolization, and/or swelling. Electron microscopy revealed crystals in patients #1-2 and non-crystalline particles within numerous/large/dysmorphic lysosomes in patients #3-5. Ig-LC restriction was demonstrated in the proximal tubule as κ-type in patients #1-2 and as λ-type in patients #3-5 by immunohistochemistry and immunofluorescence. Immunohistochemical staining showed diffuse positivity to κ- and λ-LC, although immunofluorescent staining for κ-LC was focal and weak. LCPT has diverse clinicopathological characteristics and subtle morphological alterations, which necessitate ancillary tests for diagnosis. CONCLUSIONS: We introduced immunohistochemical staining for Ig-LC as a useful tool for the diagnosis of LCPT, especially in the case of κ-type crystals.

An autopsy case of amyloid tubulopathy exhibiting characteristic spheroid-type deposition.

An 84-year-old woman with a history of haemodialysis for renal failure from approximately 1 year before death. Autopsy revealed numerous spheroid-type amyloid deposits in the kidney that were observed mainly in the interstitium but not the glomeruli and vessels. In addition, intracytoplasmic small globular amyloid deposits in the proximal tubules in addition to amyloid casts were identified. Immunohistochemistry and proteomic analyses indicated these deposits were composed of λ light chains. Amyloid deposition was also found in the lung and heart. λ-type monoclonal protein was detected in her serum and increased numbers of CD138-positive cells with λ-restriction was observed in the bone marrow. The case was diagnosed as amyloid tubulopathy (AT) associated with systemic ALλ amyloidosis related to plasma cell neoplasm. This case indicates that AT is associated with ALλ amyloidosis, which developed systemically with characteristic amyloid deposition forms. These pathological features may be associated with her rapid progressive renal failure.

Remission of light chain proximal tubulopathy in IgG λ-type multiple myeloma by lenalidomide and dexamethasone therapy.

Light chain proximal tubulopathy is a rare manifestation of monoclonal gammopathy. A 73-year-old Japanese woman was noted to have urinary protein and hypertension on health examination and visited the regional clinic. She was noted to have IgG λ M protein and suspected of multiple myeloma. She was referred to us with massive proteinuria (7.5 g/g creatinine) and Bence Jones proteinuria without renal dysfunction. A renal biopsy revealed no glomerular abnormalities, but a tubular cast was observed partially in tubules without tubular atrophy or a crystalline structure. Direct Fast Scarlet staining was absent both in glomerulus and vascular wall. Immunofluorescence revealed λ light chain (LC) staining in the proximal tubules. Electron microscopy revealed nonspecific findings including increased lysosomes with irregular contours and mottled appearance. A bone marrow biopsy revealed plasma cell proliferation (35%) and multiple myeloma immunoglobulin G λ type. She showed progressive anemia and decrease of eGFR with elevated level of urinary ß-2 microglobulin. She was treated with lenalidomide + dexamethasone (Ld). With Ld therapy, she achieved hematologic and nephrologic remission reducing the free LC, λ/κ ratio, urinary protein level, and urinary ß-2 microglobulin level.

Proximal Tubulopathy With Fibrillary Inclusions: A Rare Manifestation of Lymphoma-Associated Monoclonal Gammopathy of Renal Significance (MGRS).

Light chain proximal tubulopathy is a rare M-proteinemia-related nephropathy. The inclusions, composed of light chains in light chain proximal tubulopathy, are generally crystalline, and most exhibit a rhombic shape. Noncrystalline structures, such as rods or needle shapes, may also be present. In our patient, one of the noncrystalline structures, fibrillary inclusions in the cytoplasm, were observed, as previously reported in only 4 patients whose primary disease was either multiple myeloma or monoclonal gammopathy of renal significance. This is the first report involving lymphoma. Early diagnosis of light chain proximal tubulopathy is important because those who undergo chemotherapy have an improved kidney prognosis. However, in cases of kidney involvement with blood disorders, thrombocytopenia is often present. Therefore, in our case, open kidney biopsy was selected. Noncrystalline light chain proximal tubulopathy is believed to be less likely to cause Fanconi syndrome. However, Fanconi syndrome was observed in 3 of the 4 patients with fibrillary inclusions. In our case, hypouricemia was improved by chemotherapy, suggesting that the patient presented with Fanconi syndrome. Noncrystalline light chain proximal tubulopathy with fibrillary inclusions may cause Fanconi syndrome, similar to crystalline light chain proximal tubulopathy. We report a case of light chain proximal tubulopathy with fibrillary inclusions complicated by low-grade B-cell lymphoma in which early treatment was successful.

Lambda Light Chain Non-crystalline Proximal Tubulopathy with IgD Lambda Myeloma.

Light Chain Proximal Tubulopathy (LCPT) is a rare form of paraprotein-related kidney disease in which monoclonal free light chains damage the proximal renal tubular epithelial cells. We herein report the case of a 78-year-old woman who presented with anemia and kidney dysfunction. Serum and urine protein electrophoresis analyses revealed a monoclonal IgD and λ free light chains. Proximal tubular injury and the accumulation of λ light chains were found by kidney biopsy. Electron microscopy revealed no organized structure suggestive of crystals. LCPT was caused by IgD lambda myeloma and bortezomib and dexamethasone therapy led to very good partial response (VGPR) without a worsening of the kidney function.