Widespread crystalline inclusions affecting podocytes, tubular cells and interstitial histiocytes in the myeloma kidney

Monoclonal immunoglobulin crystalline nephropathies

Monoclonal Ig crystalline nephropathies are rare lesions resulting from precipitation of monoclonal Igs in the kidney as crystalline inclusions. They can be categorized into lesions with predominant intracellular crystals (light chain [LC] proximal tubulopathy, LC crystal-storing histiocytosis, and LC crystalline podocytopathy) and lesions with predominant extracellular crystals (crystalglobulin-induced nephropathy and crystalline variant of LC cast nephropathy). The majority of these lesions are associated with low tumor burden lymphoproliferative disorders, with the exception of crystalline variant of LC cast nephropathy. Extrarenal involvement (e.g., skin and cornea) is frequent. Kidney biopsy is the cornerstone for diagnosis, which often requires electron microscopy and antigen retrieval. A thorough hematologic workup and evaluation of extrarenal involvement is mandatory for management. Treatment of these lesions is with clone-directed therapy, with the goal of achieving hematologic very good partial response or complete response, which preserves or improves kidney function. In vitro and in vivo studies, animal models, and novel sequencing techniques have been invaluable tools to understand the pathogenesis of LC proximal tubulopathy and can be used to increase our limited knowledge of the pathogenesis of the other monoclonal Ig crystalline nephropathies. This review provides an update on the pathology, renal and hematologic characteristics, extrarenal manifestations, prognosis, treatment, and pathogenesis of monoclonal Ig crystalline nephropathies.

Pathological characteristics of light chain crystalline podocytopathy

Monoclonal immunoglobulin light chain (LC) crystalline inclusions within podocytes are rare, poorly characterized entities. To provide more insight, we now present the first clinicopathologic series of LC crystalline podocytopathy (LCCP) encompassing 25 patients (68% male, median age 56 years). Most (80%) patients presented with proteinuria and chronic kidney disease, with nephrotic syndrome in 28%. Crystalline keratopathy and Fanconi syndrome were present in 22% and 10%, respectively. The hematologic condition was monoclonal gammopathy of renal significance (MGRS) in 55% and multiple myeloma in 45%. The serum monoclonal immunoglobulin was IgG κappa in 86%. Histologically, 60% exhibited focal segmental glomerulosclerosis (FSGS), often collapsing. Ultrastructurally, podocyte LC crystals were numerous with variable effacement of foot processes. Crystals were also present in proximal tubular cells as light chain proximal tubulopathy (LCPT) in 80% and in interstitial histiocytes in 36%. Significantly, frozen-section immunofluorescence failed to reveal the LC composition of crystals in 88%, requiring paraffin-immunofluorescence or immunohistochemistry, with identification of kappa LC in 87%. The LC variable region gene segment, determined by mass spectrometry of glomeruli or bone marrow plasma cell sequencing, was IGKV1-33 in four and IGKV3-20 in one. Among 21 patients who received anti-plasma cell-directed chemotherapy, 50% achieved a kidney response, which depended on a deep hematologic response. After a median follow-up of 36 months, 26% progressed to kidney failure and 17% died. The mean kidney failure-free survival was 57.6 months and was worse in those with FSGS. In sum, LCCP is rare, mostly associates with IgG κappa MGRS, and frequently has concurrent LCPT, although Fanconi syndrome is uncommon. Paraffin-immunofluorescence and electron microscopy are essential to prevent misdiagnosis as primary FSGS since kidney survival depends on early diagnosis and subsequent clone-directed therapy.

Crystal-Induced Podocytopathy Producing Collapsing Focal Segmental Glomerulosclerosis in Monoclonal Gammopathy of Renal Significance: A Case Report

Monoclonal gammopathy–associated crystalline podocytopathy causing collapsing focal segmental glomerulosclerosis (FSGS) is very rare and has been associated with pamidronate therapy. We present the case of a 53-year-old man with vision loss secondary to corneal crystals deposition, nephrotic-range proteinuria, and reduced glomerular filtration rate without associated comorbid conditions. Two kidney biopsies were initially reported as primary FSGS but the patient did not respond to high-dose corticosteroid immunosuppression therapy. Repeat review of biopsies with additional electron microscopy analysis revealed crystalline inclusions in podocytes leading to collapsing FSGS. Subsequent workup revealed an immunoglobulin G κ serum monoclonal protein. Bone marrow biopsy revealed 5% κ-restricted plasma cells with cytoplasmic crystalline inclusions. To our knowledge, this is the first case of monoclonal gammopathy of clinical significance manifesting as crystalline podocytopathy leading to collapsing FSGS and keratopathy leading to vision loss. Crystalline podocytopathy should be considered in the differential diagnosis of collapsing glomerulopathy, and careful ultrastructural examination of the kidney biopsy specimen is crucial to establish this diagnosis.

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.

Renal crystal-storing histiocytosis involving glomeruli - A comprehensive clinicopathologic analysis

Crystal-storing histiocytosis (CSH) is a rare manifestation of monoclonal gammopathy in which histiocytes containing monoclonal proteins in their cytoplasm are found in various organs of the body including the kidney. Within the kidney, these monoclonal crystal-laden histiocytes have been described to occur in the interstitium (most commonly) or in the glomerular mesangium. CSH within glomerular capillary loops has rarely been reported. We describe three cases of CSH primarily affecting the glomerular capillaries and review the literature of CSH in general. Twenty cases of CSH involving the kidney are present in the literature; three describe CSH in glomeruli, only one of which showed histiocytes predominantly in glomerular capillary loops, while 15 had predominantly or solely interstitial CSH. Most cases involve IgG kappa crystals with only one case involving lambda light chain. Patients with CSH predominantly involving the glomerular capillaries showed a trend toward lower serum creatinine and proteinuria at presentation, and several patients with CSH lacked a definitive diagnosis of a monoclonal gammopathy at the time of diagnosis, emphasizing the role that kidney biopsy and particularly electron microscopy play in diagnosis of this entity.

A case report of crystalline light chain inclusion-associated kidney disease affecting podocytes but without Fanconi syndrome: A clonal analysis of pathological monoclonal light chain

RATIONALE

Crystalline light chain inclusion-associated kidney disease affects mainly tubular epithelial cells and is often clinically manifested as Fanconi syndrome. However, only very few case reports about the crystalline deposits within the podocytes are available, and the nature of the pathogenic monoclonal light chain implicated in these cases is still unknown. We report a case of crystalline inclusion-associated kidney disease manifested as crystalline podocytopathy in which we identified the complete structure of the pathogenic monoclonal light chain as belonging to the germ-line gene of Vκ1-39.

PATIENT CONCERNS

We describe a 65-year-old woman with crystalline light chain inclusion-associated kidney disease showing mild proteinuria and renal insufficiency with monoclonal gammopathy of undetermined significance without Fanconi syndrome. She had crystalline inclusions mainly within podocytes, tubular epithelial cells and histiocytes in the kidney. Light microscopy showed vacuolation of podocytes and tubular epithelial cells, while eosin negative pale needle-like crystals were present within these cells. Electron microscopy showed accumulation of club-like crystals with high electron density in podocytes, proximal tubular epithelial cells and interstitial histiocytes. Clonal analysis revealed that a pathogenic monoclonal light chain was derived from germline gene, Vκ1-39.

DIAGNOSES

The diagnosis of crystalline light chain inclusion-associated kidney disease was made.

INTERVENTIONS AND OUTCOMES

Bortezomib and dexamethasone were started and her renal function improved to eGFR 36 mL/min/1.73 m after 9 courses of therapy.

LESSONS

Patients with light chain crystalline podocytopathy may have a similar pathogenic monoclonal light chain derived from the same germline gene, Vκ1-39, to that of patients with light chain proximal tubulopathy.

Multiple myeloma with crystal-storing histiocytosis, crystalline podocytopathy, and light chain proximal tubulopathy, revealed by retinal abnormalities: A case report

RATIONALE

Crystal sorting histiocytosis (CSH) is a rare disorder that is morphologically characterized by the accumulation of monoclonal immunoglobulin crystals, predominantly of a kappa light chain type, within lysosomes of macrophages. CSH may result in a variety of clinical manifestations depending on the involved organs. In this case report, we aim to describe a patient with ophthalmic manifestations which lead to the diagnosis of multiple myeloma with crystal-storing histiocytosis, crystalline podocytopathy, and light chain proximal tubulopathy.

PATIENT CONCERNS

A 60-year-old male patient presented with progressive bilateral decreased vision for 2 years.

DIAGNOSIS

Ophthalmic explorations showed bilateral macular and papillary edema, and multiple crystalline deposits in the anterior stromal cornea and in the retina. Laboratory tests showed nephrotic syndrome and renal dysfunction. Further work-up revealed IgG kappa multiple myeloma, with biopsy-proven combined crystalline podocytopathy and tubulopathy.

INTERVENTIONS

The patient received chemotherapy (bortezomib, cyclophosphamide, and dexamethasone for 3 cycles, then bortezomib, lenalidomide, and dexamethasone).

OUTCOMES

Despite partial hematologic response and improvement of the papilledema and macular edema, the patient developed dialysis-dependent end-stage renal failure.

LESSONS

This report, highlighting the protean presentation of paraprotein-mediated injuries, provides additional information on the ocular anomalies not previously described that may be associated with crystal-storing histiocytosis.

Monoclonal light chain crystalline podocytopathy and tubulopathy associated with monoclonal gammopathy of renal significance: a case report and literature review

Background

Monoclonal gammopathy of renal significance (MGRS) is a recently defined group of renal diseases caused by monoclonal immunoglobulin secreted by nonmalignant proliferative B cell or plasma cell. Monoclonal immunoglobulin can form different types of structures deposited in renal tissue, including fibrils, granules, microtubules, crystals and casts, and has mostly been reported in multiple myeloma patients. Here we report a rare case with κ light chain crystals in both podocytes and tubular epithelial cells associated with MGRS, which adds more information to the spectrum of MGRS-related renal diseases.

Case presentation

A 53-year old woman presented with albumin–predominant moderate proteinuria and renal failure. She had monoclonal IgGκ in the serum and monoclonal IgGκ plus free κ in the urine. Multiple myeloma and lymphoproliferative disorders were excluded. Renal biopsy confirmed κ-restricted crystal-storing renal disease involving the podocytes and proximal tubular epithelial cells. The patient was treated with bortezomib followed by lenalidomide-based chemotherapy, and renal function was stable after 1 year of follow-up.

Conclusions

This is a rare case of combined crystalline podocytopathy and tubulopathy associated with MGRS, in which diagnosis was dependent on electron and immuno-electron microscopy.

Light Chain Podocytopathy Mimicking Recurrent Focal Segmental Glomerulosclerosis

Kidney injury related to paraproteinemia is common and typically occurs after the fourth decade of life in association with an underlying plasma cell dyscrasia or other lymphoproliferative disease. Kidney transplantation in paraprotein-related kidney disease can be successful in conjunction with treatment of the underlying hematopoietic process; however, when hematologic response to therapy is not achieved, recurrent kidney injury is frequently seen. We describe a young male patient who presented at the age of 23 years with end-stage kidney disease thought to be secondary to focal segmental glomerulosclerosis; this patient ultimately received two kidney allografts. He experienced recurrent proteinuria in both kidneys, with a biopsy from his second allograft showing kappa-restricted crystalline light chain podocytopathy, which was identified in both his native and first allograft kidneys upon retrospective review. Recurrent light chain podocytopathy has not been previously reported but poses a diagnostic challenge as it can mimic focal segmental glomerulosclerosis, particularly in young patients in whom paraprotein-related kidney injury is usually not suspected.

Renal Light Chain Deposition Associated with the Formation of Intracellular Crystalline Inclusion Bodies in Podocytes: A Rare Case Report

We herein report the case of an elderly woman with bone pain and proteinuria as the main clinical manifestations. The patient was diagnosed with the IgG κ type of multiple myeloma. Her renal pathology consisted of widespread κ light chain protein deposition associated with the formation of large quantities of rod-like crystals in podocytes. This phenomenon is very rare. We explored the significance of this crystal formation via a detailed and descriptive analysis and also performed a literature review, thus providing data to increase the available information about this type of disease.

Crystalloid podocytopathy with focal segmental glomerulosclerosis in PCM: a case report

Background

Crystalloid podocytopathy with focal segmental glomerulosclerosis in plasma cell myeloma (PCM) is rare.

Case Presentation

We present a case of crystalline deposition in the bone marrow (BM) and various renal cells with only proteinuria as a symptom. As workup for proteinuria, a renal biopsy sample was obtained. EM showed multiple crystalline depositions in renal tubular cells and podocytes. Focal segmental glomerulosclerosis with crystalloid podocytopathy was diagnosed. Because monoclonal gammopathy was detected in the serum and urine, a BM study was also performed. Plasma cells with needle-shaped inclusion bodies were observed. The crystalline deposits in the plasma cells and podocytes were positive for Masson’s trichrome and kappa light-chain staining. These findings indicated that the crystalline deposits originated from paraprotein. The case showed a rare process of focal segmental glomerulosclerosis via crystalline deposition in podocytes in plasma cell myeloma.

Conclusions

Crystalloid podocytopathy is a likely cause of renal damage such as FSGS in PCM, although it is an uncommon mechanism for myeloma kidney.

Ultrastructural study of electron dense deposits in renal tubular basement membrane: prevalence and relationship to epithelial atrophy

This study reports the prevalence of immune deposits associated with the proximal and distal tubules in a series of routine renal biopsies received in our department during a single calendar year. From 87 cases, 65 (74%) were found to have glomerular immune deposits by immunofluorescence. Tubular immune deposits were found in 12 cases (18%), 3 of which had no glomerular deposits. By transmission electron microscopy (EM), 58 cases (66%) were found to have deposits of granular or vesicular material associated with the tubular basement membranes (TBM). Finely granular electron dense deposits appeared to correspond to the immune deposits seen by immunofluorescence microscopy (IF) and may be a sensitive marker of immune deposition.

Crystalloid glomerulopathy in monoclonal gammopathy of renal significance (MGRS)

We report a case of monoclonal gammopathy of renal significance in a 63-year-old man who presented with nephrotic-range proteinuria and renal insufficiency. The kidney biopsy showed a membranoproliferative glomerulonephritis pattern with extensive crystalloid deposits in the glomerular capillary endothelial cells and very few in the tubular epithelial cells. The immunoperoxidase staining showed kappa light chain restriction. Subsequently, the bone marrow showed 6% plasma cells which confirmed the diagnosis of monoclonal gammopathy of renal significance. He responded well to bortezomib treatment with resolution of the nephrotic syndrome and normalization of renal function after 7 months.

Combined crystalline podocytopathy and tubulopathy associated with multiple myeloma

Lymphoplasmacytic neoplasms cause a wide range of injuries to the kidney exemplified by light chain cast nephropathy and amyloidosis. Filtered paraproteins can also accumulate within kidney cells and cause direct cytotoxic injury. Rarely, paraproteins that are resistant to proteolysis can crystallize within proximal tubules and cause acute tubular injury. In contrast, accumulation of crystallized paraproteins in other kidney cells, especially podocytes, is exceptional. Here, we report the finding of crystalline inclusions within podocytes and proximal tubules in a patient who presented with a combined nephrotic syndrome and Fanconi syndrome. Further workup revealed previously unsuspected multiple myeloma and elevated serum free light chains, highlighting the protean presentation of paraprotein-mediated injuries to the kidney.

Crystal-storing histiocytosis: report of a case, review of the literature (80 cases) and a proposed classification

We report a case of crystal storing histiocytosis (CSH) of the upper lip and cheek in a 51-year-old woman and review the clinicopathologic features of 80 cases in the literature. These occurred in 41 men and 39 women with a respective mean age of 59 and 61 years (range 17-81 years). Forty-six patients (58%) had localized CSH, and, of these, 16 (35%) occurred in the head and neck, with the most common site being the eye/orbit. The remaining 34 patients (42%) had generalized CSH primarily involving bone marrow, liver, lymph nodes, spleen and/or kidney. Regardless of whether the CSH was localized or generalized, the vast majority of patients (90%) had an underlying lymphoproliferative or plasma cell disorder, especially multiple myeloma, lymphoplasmacytic lymphoma, or monoclonal gammopathy of undetermined significance. In 7 cases (8.8%), the CSH was associated with a variety of benign disorders, often with an inflammatory background, and no evidence of a clonal lymphoproliferative or plasma cell disorder. Treatment and prognosis varied according to the underlying disease. A classification of CSH based on etiology and/or associated disease and chemical composition of the crystal is proposed, rare non-immunoglobulin variants of CSH are discussed, and a differential diagnosis of other potentially confusing lesions is provided.

Expanding the pathologic spectrum of immunoglobulin light chain proximal tubulopathy

CONTEXT

In plasma cell dyscrasias, involvement of the distal tubules is frequent and well characterized. In contrast, proximal tubules have only rarely been reported to show diagnostic pathology such as intracytoplasmic crystals.

OBJECTIVE

To look for additional morphologic features that might be helpful in the diagnosis of proximal tubulopathy associated with an underlying plasma cell dyscrasia.

DESIGN

We examined patients presenting with nonspecific renal symptoms who were found to have light chain restriction limited to proximal tubular epithelium by immunofluorescence. We correlated these results with light microscopy, electron microscopy, and the clinical findings.

RESULTS

By immunofluorescence, 5 patients had light chain restriction in proximal tubular epithelium. By light microscopy, only 1 patient had focal rhomboid crystals in the proximal tubular epithelium; all other biopsies failed to show any discernible pathology within the proximal tubules or elsewhere in the kidney. By electron microscopy, proximal tubules from 2 patients showed crystals with a latticelike structure, whereas the remaining 3 patients had only prominent phagolysosomes. However, by immunoelectron microscopy, the lysosomal content showed light chain restriction (in 2 cases studied). Post-kidney biopsy, all patients were diagnosed with multiple myeloma or plasma cell dyscrasia. One patient developed renal failure and had recurrence of crystals in the allograft.

CONCLUSIONS

Light chain proximal tubulopathy may be associated with the presence of crystals or with the presence of phagolysosomes with light chain restriction as the sole abnormality. Both kappa and lambda light chains may be involved. The prognosis is variable and the pathology may recur in transplants.