Crystalloid glomerulopathy in monoclonal gammopathy of renal significance (MGRS)

Combined renal proximal tubulopathy and crystal storing histiocytosis in a patient with κ light chain multiple myeloma

Multiple myeloma accounts for 10-15% of all hematologic malignancies, and 20% of deaths related to cancers of the blood and bone marrow. Diagnosis is defined by the presence of a serum monoclonal spike (M-spike) of more than 3 g/dL or more than 10% clonal plasma cells in the bone marrow and at least one myeloma-defining event, such as hypercalcemia, anemia, bone lesions, or renal impairment. The kidney is a major target organ, and renal impairment is frequently the first manifestation of the disease. Renal damage occurs in up to 40% of patients and 10-20% will require dialysis. Monoclonal immunoglobulin light chains are the major causes of renal complications in multiple myeloma. Glomerular disease, with the deposition of monoclonal immunoglobulins or their components, includes monoclonal immunoglobulin deposition disease, AL or AH amyloidosis, type I cryoglobulinemia, proliferative glomerulonephritis with monoclonal IgG deposits, immunotactoid glomerulopathy, and fibrillary glomerulonephritis. In addition, tubulointerstitial diseases with the deposition of monoclonal immunoglobulins or their components, are constituted by light chain cast nephropathy, light chain proximal tubulopathy, and crystal-storing histiocytosis.

We report the case of a 66-year-old woman who presented with albumin-predominant moderate proteinuria and renal failure. Serum and urine immunofixation electrophoresis showed monoclonal κ light chain in both. Renal biopsy confirmed κ-restricted crystal-storing renal disease involving proximal tubular epithelial cells and crystal storing histiocytosis. Multiple myeloma with crystal storing histiocytosis was discovered in bone marrow biopsy. Thus, we present an unusual case of a myeloma patient presenting light chain proximal tubulopathy and crystal-storing histiocytosis both in the kidney and in the bone marrow.

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.

Crystalglobulin-associated nephropathy presenting as MGRS in a case of monoclonal B-cell lymphocytosis: a case report

BACKGROUND

Crystalglobulin-associated nephropathy (CAN), a rare subtype of monoclonal gammopathy, usually associated with multiple myeloma and occasionally monoclonal gammopathy of uncertain significance (MGUS), is characterized by occluding monoclonal pseudothrombi within renal glomerular capillaries and/or interstitial arterioles. Ultrastructurally, these pseudothrombi are unique for having a crystalline substructure. We describe a case of an adult patient with monoclonal B-cell lymphocytosis (MBL) and acute renal failure whose kidney biopsy revealed a rare diagnosis of CAN.

CASE PRESENTATION

A 63-year old male presented with a 2-month history of edema, arthralgia and malaise. He had acute kidney injury with hematoproteinuria on urine analysis. Serum and urine protein electrophoresis were both negative. A renal biopsy however revealed features of CAN. Organomegaly, bone pain and lymphadenopathy were absent. A repeat serum electrophoresis was positive for IgA kappa and a free light chain assay showed elevated free kappa light chains. Flow cytometry done subsequently revealed a diagnosis of MBL, chronic lymphocytic leukemia (CLL) type.

CONCLUSION

CAN in association with MBL/CLL has not been previously described in literature, and our case highlights yet another instance of monoclonal gammopathy of renal significance (MGRS) where a small B-cell clone resulted in extensive renal pathology without systemic manifestations.

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.

Monoclonal gammopathy of renal significance: clinical manifestation, pathogenic characteristic and treatment

Monoclonal gammopathy of renal significance (MGRS) is a group of renal disorders caused by a monoclonal immunoglobulin (MIg) secreted by a dangerous plasmatic/B-cell clone hyperplasia through MIg deposition or dysfunction of complement pathway, with increasing risk of progress to end stage renal disease (ESRD) and the underlying hematologic malignancy. The combination of renal biopsy, complete laboratory examination and bone marrow biopsy is an indispensable diagnostic tool for MGRS to identify accurately and unequivocally the pathogenic monoclonal MIg and provide guidance to treatment. Treatment of MGRS is composed of conventional therapy, chemotherapy, and stem cell transplantation to target the underlying clone and eliminate the noxious MIg on the basis of clinical data of some retrospective studies and a small amount of prospective trial. In addition, it is worthwhile point out assessment of therapeutic effect is significantly relevant for renal and overall prognosis. Thus, by comprehensively analyzing the clinical manifestations and pathogenic characteristic of MGRS, early recognition and prompt treatment can improve the prognosis and prevent post-translation recurrence with multidisciplinary cooperation.

Monoclonal Gammopathy of Renal Significance Presenting as Cryoglobulinemic Glomerulonephritis: A Case Report and Review of Literature

Monoclonal gammopathy of renal significance (MGRS) can present with myriad of morphological features. We report a case of MGRS in a 46-year-old man who presented with nephrotic-range proteinuria and renal insufficiency. Renal biopsy showed amorphous eosinophilic periodic acid–Schiff positive deposits in capillary loops and lamda light chain positivity on immunofluorescence, suggestive of cyoglobulinemic glomerulonephritis. Serum cryoglobulins were positive. Serum immunoelectrophoresis and immunofixation showed a M band of 0.5 g/dl of IgG lambda type. Bone marrow showed 8% of plasma cells which confirmed the diagnosis of MGRS.

The Complexity and Heterogeneity of Monoclonal Immunoglobulin-Associated Renal Diseases

Monoclonal gammopathies are characterized by the overproduction of monoclonal Ig (MIg) detectable in the serum or urine resulting from a clonal proliferation of plasma cells or B lymphocytes. The underlying hematologic conditions range from malignant neoplasms of plasma cells or B lymphocytes, including multiple myeloma and B-cell lymphoproliferative disorders, to nonmalignant small clonal proliferations. The term MGUS implies presence of an MIg in the setting of a "benign" hematologic condition without renal or other end organ damage. The term MGRS was recently introduced to indicate monoclonal gammopathy with MIg-associated renal disease in the absence of hematologic malignancy. Most MIg-associated renal diseases result from the direct deposition of nephrotoxic MIg or its light- or heavy-chain fragments in various renal tissue compartments. Immunofluorescence microscopy is essential to identify the offending MIg and define its tissue distribution. Mass spectrometry is helpful in difficult cases. Conditions caused by direct tissue deposition of MIg include common disorders, such as cast nephropathy, amyloidosis, and MIg deposition diseases, as well as uncommon disorders, such as immunotactoid glomerulopathy, proliferative GN with MIg deposits, light-chain proximal tubulopathy, and the rare entities of crystal-storing histiocytosis and crystalglobulinemia. Indirect mechanisms of MIg-induced renal disease can cause C3 glomerulopathy or thrombotic microangiopathy without tissue MIg deposits. Treatment of MIg-associated renal disease is aimed at eliminating the clonal plasma cell or B-cell population as appropriate. Both the renal and the underlying hematologic disorders influence the management and prognosis of MIg-associated renal diseases.

Monoclonal gammopathy of renal significance (MGRS) increases the risk for progression to multiple myeloma: an observational study of 2935 MGUS patients

Purpose

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignancy preceding multiple myeloma (MM) or related disorders. In MGUS, renal impairment caused by deposition of the monoclonal immunoglobulins or free light-chains monoclonal gammopathy of renal significance (MGRS) is often associated with high morbidity and mortality. We analysed the prevalence of renal impairment, clinical features and the long-term outcome in 2935 patients with MGUS.

Methods

Between 1/2000 and 8/2016, 2935 adult patients with MGUS were identified in our database.

Results

In 44/2935 (1.5%) patients MGRS was diagnosed. In MGRS patients, significantly more progressions to MM were observed than in MGUS patients (18% vs. 3%; P<0.001). MGRS patients showed a higher risk for progression (HR 3.3 [1.5-7.4]) in the Cox model. Median time to progression was 23 years for MGUS and 18.8 years for MGRS patients. Corresponding progression rate was 8.8 [7.2-10.7] per 1000 patient-years (py) for MGUS patients and 30.6 [15.3–61] for the MGRS group. Risk for progression within the first year after diagnosis was 1% [0.6-1.4] in the MGUS group and 10% [4-29] among MGRS patients.

Conclusion

The significantly higher risk for progression to MM means MGRS patients should be monitored carefully and treated in a specialized centre.

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.

Spectrum of manifestations of monoclonal gammopathy-associated renal lesions

PURPOSE OF REVIEW

Monoclonal gammopathies result from an overt malignant process, such as multiple myeloma, or a premalignant process, such as monoclonal gammopathy of undetermined significance. The kidney is often affected in the setting of a monoclonal gammopathy. The term 'monoclonal gammopathy of renal significance (MGRS)' was recently introduced to draw attention to renal diseases related to the monoclonal gammopathy. In this review, we define the pathology of these monoclonal gammopathy-associated kidney diseases.

RECENT FINDINGS

Renal disease can be caused by deposition of the monoclonal immunoglobulin (direct mechanism) or by activation of the alternative pathway of complement by the monoclonal immunoglobulin (indirect mechanism). The deposition of monoclonal immunoglobulin can affect the glomeruli, tubules, and the interstitium and vessels. The glomerular diseases include proliferative glomerulonephritis with monoclonal immunoglobulin deposits, immunotactoid glomerulopathy, and, less commonly, fibrillary glomerulonephritis. Tubular lesions associated with monoclonal immunoglobulin include cast nephropathy and light-chain proximal tubulopathy. Lesions involving the glomeruli, tubules, interstitium or vessels include amyloidosis and monoclonal immunoglobulin deposition diseases. Rarely, monoclonal immunoglobulin may also cause C3 glomerulopathy or atypical hemolytic uremic syndrome by interfering with the regulation of the alternative pathway of complement.

SUMMARY

Monoclonal gammopathy are associated with a variety of kidney diseases. The monoclonal gammopathy-associated renal diseases are distinct in their pathogenesis, kidney biopsy findings, clinical presentation, progression, prognosis, and treatment. The term monoclonal gammopathy of renal significance helps highlight patients who have renal disease secondary to monoclonal immunoglobulin secreted by a premalignant or malignant clone, but is not a disease or diagnosis in itself.

Histiocytic and Nonhistiocytic Glomerular Lesions: Foam Cells and Their Mimickers

Numerous histiocytes are sometimes noted in glomeruli, giving rise to a foamy-appearing glomerulus. Foamy-appearing glomeruli may also be noted in conditions that do not contain numerous histiocytes. These disease entities are rare, have different underlying causes and pathophysiology, and can cause a diagnostic dilemma. We have observed this histiocytic/foamy glomerular change on the kidney biopsy specimen in 5 different disease entities: crystal-storing histiocytosis, histiocytic glomerulopathy associated with macrophage-activating syndrome, thrombotic microangiopathy, lecithin-cholesterol acyltransferase deficiency, and lipoprotein glomerulopathy. We describe and compare the kidney biopsy findings of these histiocytic and foamy-appearing entities. It is important to recognize the kidney biopsy findings of these rare conditions to correctly evaluate and identify the cause and manage these patients.