Pathology of glomerular deposition diseases

Acute Kidney Injury in Monoclonal Gammopathies

Monoclonal gammopathies (MG) encompass a variety of disorders related to clonal expansion and/or malignant transformation of B lymphocytes. Deposition of free immunoglobulin (Ig) components (light or heavy chains, LC/HC) within the kidney during MG may result over time in multiple types and degrees of injury, including acute kidney injury (AKI). AKI is generally a consequence of tubular obstruction by luminal aggregates of LC, a pattern known as “cast nephropathy”. Monoclonal Ig LC can also be found as intracellular crystals in glomerular podocytes or proximal tubular cells. Proliferative glomerulonephritis with monoclonal Ig deposits is another, less frequent form of kidney injury with a sizable impact on renal function. Hypercalcemia (in turn related to bone reabsorption triggered by proliferating plasmacytoid B cells) may lead to AKI via functional mechanisms. Pharmacologic treatment of MG may also result in additional renal injury due to local toxicity or the tumor lysis syndrome. The present review focuses on AKI complicating MG, evaluating predictors, risk factors, mechanisms of damage, prognosis, and options for treatment.

Immunotactoid Glomerulopathy with Nontuberculous Mycobacterial Infection: A Novel Association

A 70-year-old woman underwent a renal biopsy due to nephrotic syndrome. She had suffered from nontuberculous mycobacterial infection (NTM) for 14 years. The patient was diagnosed as having membranoproliferative glomerulonephritis (MPGN) type 3 and immunoglobulin (Ig)-associated MPGN based upon LM/erythromycin and IF findings, respectively. In high-magnification imaging, electron-dense deposits showed immunotactoid glomerulopathy (ITG). There was no evidence of hematological cancer, and the patient improved after receiving treatments for NTM. To the best of our knowledge, this patient is the first to show an association between ITG and NTM. Although ITG is generally considered as related to lymphoproliferative disease, it is suggested that ITG is driven by bacterial infection and is a potential outcome of Ig-associated MPGN.

Monoclonal Gammopathies of Renal Significance: Renal Biopsy and Beyond

Monoclonal Gammopathies of Renal Significance (MGRS) are a rather heterogeneous group of renal disorders caused by a circulating monoclonal (MC) immunoglobulin (Ig) component, often in the absence of multiple myeloma (MM) or another clinically relevant lymphoproliferative disorder. Nevertheless, substantial kidney damage could occur, despite the "benign" features of the bone-marrow biopsy. One example is renal amyloidosis, often linked to a small clone of plasma cells, without the invasive features of MM. However, patients with amyloidosis may present with a nephrotic syndrome and renal failure, eventually leading to end-stage kidney disease. At the same time, other organs, such as the heart and the liver, may be severely damaged by Ig light chains or amyloid deposits, occasionally resulting in fatal arrhythmias and/or organ failure. Acute kidney injury (AKI) may as well result from massive excretion of MC proteins, with deposition disease in glomeruli or renal tubules, not rarely obstructed by luminal aggregates, or "casts". Proliferative glomerulonephritis with monoclonal Ig deposits is another, less frequent clinical presentation of an MGRS. The present review deals with the implications of MGRS for renal function and prognosis, and the potential of tools, such as the renal biopsy, for assessing clinical risk and guiding therapy of the underlying condition.

The pathogenesis of renal injury and treatment in light chain deposition disease

Light chain deposition disease (LCDD) is a rare clinical disorder. The deposition of light chain immunoglobulins mainly affects the kidneys, which have different characteristics than other tissues. To date, the therapeutic approach for the treatment of LCDD has no evidence-based consensus, and clinical experience of reported cases guides current disease management strategies. The present systematic review investigates and summarizes the pathological mechanisms of renal injury and the subsequent treatments for LCDD.

Proliferative glomerulonephritis with unusual microlamellar organized deposits related to monoclonal immunoglobulin G3 (IgG3) kappa

A 71-year-old woman presented with massive proteinuria and microhematuria. Renal biopsy showed diffuse global membranoproliferative and endocapillary proliferative lesions with leukocytic infiltration and an irregular duplication of the glomerular basement membrane on light microscopy. Immunofluorescence study showed granular deposits of monoclonal immunoglobulin G3 (IgG3) kappa, C3, and C1q in the glomeruli. Electron microscopy revealed unique structurally organized microlamellar electron-dense deposits. There was no evidence of systemic diseases such as paraproteinemia, cryoglobulinemia, or systemic lupus erythematosus. Following renal biopsy, the oral administration of mizoribine in addition to predonisolone gradually improved the patient's clinical status. So far, partial remission has continued for a year, and she has not been affected with hematopoietic or lymphoproliferative disorders. We report a case of proliferative glomerulonephritis with unusual microlamellar organized deposits related to monoclonal IgG3 kappa. Our case was immunologically identical to proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID). Therefore, we concluded that our case should be categorized as an atypical form of PGNMID, though it was difficult to diagnose using the usual diagnostic approach to glomerular diseases with organized deposits.

Light Chain Deposition Disease Diagnosed with Laser Micro-dissection, Liquid Chromatography, and Tandem Mass Spectrometry of Nodular Glomerular Lesions

A 42-year-old man developed nephrotic syndrome and rapidly progressive renal failure. Kidney biopsy demonstrated nodular glomerulosclerosis, negative Congo red staining, and no deposition of light or heavy chains. Laser micro-dissection and liquid chromatography with tandem mass spectrometry of nodular lesions revealed the presence of a kappa chain constant region and kappa III variable region, which signified light chain deposition disease. Dexamethasone and thalidomide were effective in decreasing the serum levels of free kappa light chain from 147.0 to 38.0 mg/L, eliminating proteinuria, and halting the worsening of the kidney dysfunction, with serum creatinine levels stable around 4.0 mg/dL for 3 years.

Proliferative glomerulonephritis with monoclonal IgG2κ deposit successfully treated with steroids: a case report and review of the literature

A novel form of glomerular injury with monoclonal immunoglobulin (Ig) IgG deposition, termed "proliferative glomerulonephritis (GN) with monoclonal IgG deposits" (PGNMID), is a recently described entity. PGNMID presents with various histological patterns, such as membranoproliferative GN, endocapillary proliferative GN and membranous nephropathy (MN). The deposits are composed of monoclonal immunoglobulin, most commonly IgG3 and occasionally IgG2. At present, the clinical significance of each IgG subclass and the morphological patterns of glomerular injury have not been fully investigated due to the limited number of PGNMID cases reported. The patient was a 27-year-old woman presenting with a mild degree of proteinuria and no other physical or serological abnormalities. Monoclonal Ig could not be identified in her serum or urine. Renal biopsy found features of MN with deposition of monoclonal IgG2κ. Electron microscopy examination revealed non-organised electron-dense deposits predominantly in subepithelial locations. Based on a diagnosis of PGNMID, she was treated with prednisolone and proteinuria significantly decreased in less than 4 weeks. Although the clinical outcomes of PGNMID remain to be defined, MN features may possibly be a sign of favourable prognosis-a hypothesis supported by recent reports. The absence of advanced chronic damage in the kidney, such as glomerulosclerosis or tubulointerstitial fibrosis, may also have contributed to the favourable outcome in the present case. Further studies on additional PGNMID cases that allow the correlation of morphological features and IgG subclasses with clinical outcomes are needed in order to confirm our findings and further solidify the clinical aspects of this new disease entity.

Proliferative glomerulonephritis with discrete deposition of monoclonal immunoglobulin γ1 CH 2 heavy chain and κ light chain: a new variant of monoclonal immunoglobulin deposition disease

A 45-year-old man presented with moderate proteinuria and hematuria. A renal biopsy showed mesangial/endocapillary proliferative glomerulonephritis, linear deposition of monoclonal immunoglobulin γ1 C(H) 2 heavy chain along glomerular and tubular basement membranes (GBMs and TBMs), granular deposition of κ light chain within the mesangial area, and continuous linear deposits of finely granular electron-dense materials along GBMs and TBMs. Dual immunostaining showed essentially discrete glomerular localization of γ1 C(H) 2 heavy chain and κ light chain. Monoclonal protein was not detected in urine and serum. A bone marrow aspiration showed no abnormalities. Steroid therapy led to the improvement of proteinuria and hematuria. We would classify this case as a new variant of monoclonal immunoglobulin deposition disease, light chain/heavy chain deposition disease. In contrast with light and heavy chain deposition disease, the remarkable characteristics of this variant are separate deposition of monoclonal heavy chain and light chain, deposition of largely deleted γ heavy chain lacking the C(H) 1 domain, and good response to steroid therapy.

Acute cerebral infarction in a patient with nodular glomerulopathy--atypical features and differential diagnosis

Nodular glomerulopathy is a pattern of glomerular injury observed under light microscopy that could result from several diseases presented as nephrotic syndrome clinically. Compared with venous thrombosis, cerebral infarction resulting from arterial thrombosis is relatively rare in these patients. We report an interesting case of severe nephrotic syndrome complicated with acute cerebral infarction, and renal biopsy revealed nodular glomerulopathy under light microscopy. Immunofluorescent staining was positive for λ light chain (predominant) and κ light chain, mainly in mesangial areas, and electron microscopic study showed massive amorphous acellular deposits also in mesangial areas with some local extension to subendothelial space. Congo red stain gave negative results under polarized light. The case was concluded as an atypical presentation of light chain deposition disease both pathologically and clinically.

Light chain deposition disease developing 15 years following the diagnosis of monoclonal gammopathy of undetermined significance

A 64-year-old woman was admitted because of leg edema. Fifteen years previously she had been diagnosed with monoclonal gammopathy of undetermined significance (MGUS). Urinary immunoelectrophoresis demonstrated positivity for IgA kappa light chains. Bone marrow aspiration revealed a mild plasmacytosis. Her renal biopsy specimen revealed thickened basement membrane, mesangial cell proliferation and an increase in the mesangial matrix. Immunofluorescence studies showed the deposition of kappa light chains in the capillary wall and nodular lesions. These findings confirmed a diagnosis of light chain deposit disease (LCDD) with MGUS. The development of LCDD in patients with MGUS for fifteen years is very rare.

Ultrastructural pathology of nephropathies with organized deposits: a case series

Renal organized or structured deposits are much less frequent than those with usual type immunocomplex deposits and are encountered in a wide variety of primary and systemic disorders. It has been suggested that immunoglobulins (Igs) are responsible for organized deposits. We report 5 cases who have been diagnosed and treated in our hospital. Patients were aged 52 to 72 years, three of them were males and had variable degree of renal function, from normal serum creatinine to uraemia. Proteinuria was detected in all patients while monoclonal component was present only in the serum of one subject. Ultrastructural analysis of renal specimens revealed organized deposits. Diagnoses that were made are the following: membranoproliferative glomerulonephritis with finger print, immunotactoid glomerulopathy, membranoproliferative glomerulonephritis with arched deposits, primary amyloidosis and light chain deposition disease. In systemic disorders ultrastructural pathology could be particularly valuable for correct deposits classification, precise localization and pattern of deposition of Igs.

Pathology of glomerular deposition diseases and fibrillary glomerulopathies associated with paraproteinemia and haematopoietic disorder

The primary glomerulopathies with a deposit of ultrastructural fibrillary structure, which are negative for Congo-red stain but positive for immunoglobulins, include fibrillary glomerulonephritis and immunotactoid glomerulopathy. Several paraproteinemias, including cryoglobulinemia, monoclonal gammopathy and light chain deposition disease as well as haematopoietic disorders including plasmacytoma, plasma cell dyscrasia and B cell lymphoproliferative disorders involve glomerulopathy with an ultrastructural fibrillary structure. A rare glomerulopathy with fibrillary structure showing negative stain for Congo-red and for immunoglobulins has been also reported. The pathological diagnoses of these glomerulopathies with ultrastructural fibrillary deposits can include either glomerular diseases, or paraproteinemic diseases, or haematopoietic diseases. The terminology is still confusing when glomerular diseases can be combined with paraproteinemic diseases and/or haematopoietic diseases. Therefore, the generic term, 'glomerular deposition disease', has been proposed by pathologists with a requirement for clinicians to detect autoantibodies, paraproteins and to carry out a bone marrow check. An attempt has been made to elucidate the correlation among the glomerular deposition disease, paraproteinemia and haematopoietic disorder.