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Disease Week: Monoclonal Gammopathy of Renal Significance

Disease Week: Monoclonal Gammopathy of Renal Significance   Summary: Renal disease caused by parenchymal deposition of circulating monoclonal immunoglobulins (mIg) is a well established phenomenon. Light chain cast nephropathy, light chain deposition disease and AL amyloidosis are probably the best known entities; nevertheless, the list also includes a number of less common and recently described entities, some of which are still poorly understood.  These disorders may be seen in the setting of either a B-cell or plasma cell proliferative disorder with production of a mIg. When these proliferative disorders represent an overtly malignant disease (e.g. multiple myeloma, Waldenström macroglobulinemia, high-grade...

Polyomavirus Nephropathy in Native Kidney

Polyomavirus nephropathy (PVN), predominantly caused by BK virus reactivation in the urogenital tract, is an important complication of renal allografts (reference 1). While it rarely affects the native kidney, it may be seen in the setting of chronic immunosuppression, including bone marrow transplantation, HIV infection, chemotherapy and in the setting of other solid organ transplants (reference 2). The case shown is from a 69-year-old female with a history of sarcoidosis and cirrhosis who is now 5 years post liver transplant. The patient is currently being evaluated for a progressive increase in serum creatinine. The biopsy shows significant, non-specific tubulointerstitial scarring...

Membranous Glomerulopathy in Obesity-Related Glomerulopathy

The patient is a 57-year-old female, with a history of morbid obesity and persistent mild proteinuria (approximately 1 gm), who now presents with nephrotic syndrome and a UPCR of 10.5 g/g. Renal function is normal with a serum creatinine of 0.5 mg/dl. The biopsy shows marked glomerulomegaly with focal areas of perihilar segmental glomerulosclerosis (Fig 1 and 2). Additionally, the capillary loops appear mildly thickened, with frequent subepithelial fuchsinophilic deposits on trichrome stain and diffuse and global holes and spikes seen on silver stain (Fig 3). Immunofluorescence shows global capillary loop granular staining for IgG, C3, kappa, and lambda (Fig...

Proliferative Glomerulonephritis with Monoclonal IgG Deposits

This biopsy was performed on a 58-year-old female who presented with mild proteinuria. The glomeruli show diffuse and global endocapillary hypercellularity with segmental double contour formation of the capillary loops on the silver stain (Fig 1). Immunofluorescence shows mesangial and segmental capillary wall deposits positive for IgG (3+, Fig 2), C3 (3+, not shown), C1q (1+, not shown) and lambda light chain (3+, Figure 4). Staining for kappa light chain is negative in glomeruli (Fig 3). Further immunofluorescence staining for IgG subclasses proves the deposits to be IgG3 restricted. Electron microscopy shows mesangial and segmental subendothelial immune-complex type deposits. The...

Interstitial Foam Cells

This 52-year-old female underwent a renal biopsy as part of the workup for nephrotic syndrome. The biopsy is diagnostic for PLA2R-positive membranous glomerulopathy with mild glomerular and tubulointerstitial chronic injury (not shown). Interestingly, the interstitium shows frequent clusters of interstitial foam cells (see image). While interstitial foam cells are commonly associated with Alport syndrome, they may actually be seen in a wide range of renal diseases resulting in heavy proteinuria, such as focal segmental glomerulosclerosis (FSGS), membranous glomerulopathy, IgA nephropathy and in diseases with a membranoproliferative pattern of glomerular injury. While it has been shown that interstitial foam cells contain...

Endocapillary Hypercellularity in Thrombotic Microangiopathy

This renal biopsy performed on a 14-year-old boy shows changes diagnostic of a thrombotic microangiopathy (TMA). These changes include frequent fibrin thrombi within the arteriolar lumens and glomerular hilum, endothelial swelling, mesangiolysis and focal glomerular ischemic changes (Fig 1-3). Of note, the glomeruli frequently show marked global endocapillary hypercellularity, mostly composed of swollen endothelial cells and occasional circulating inflammatory cells (Fig 4). Immunofluorescence and electron microscopy show absence of immune complex deposition (not shown). This case illustrates that a subset of cases of TMA may show endocapillary hypercellularity and is important to avoid misdiagnosing such cases as a proliferative glomerulonephritis....

Smoking-Related Glomerulopathy

A renal biopsy was performed on this 52-year-old male with a history of hypertension and heavy tobacco use, who is being worked up for nephrotic range proteinuria and increased creatinine. The glomeruli (Fig 1 and 2) show nodular mesangial matrix expansion without definitive proliferation, necrosis or crescents. Focal areas of segmental glomerulosclerosis are present. There is no evidence of immune complex or monoclonal immunoglobulin deposition by immunofluorescence or electron microscopy. Of note, electron microscopy does show global thickening of glomerular basement membranes (not shown). While non-specific, the most common cause of nodular glomerulosclerosis in the United States is diabetes mellitus/glucose...

Diabetic Glomerulosclerosis with Superimposed Diseases

Diabetic glomerulosclerosis is one of the most common causes of nephrotic range proteinuria in adults. When the clinical course of these patients is atypical, a renal biopsy is of utmost importance to rule out superimposed or other concomitant diseases. Figure 1 (PAS stain) shows a representative glomerulus from a renal biopsy performed on a 65 year old Caucasian female with longstanding history of type 2 diabetes mellitus, who experienced a sudden increase in proteinuria from a baseline UPCR of 1.2 g/g to 7.5 g/g. The glomerulus shows severe mesangial matrix expansion with frequent large nodule formation, characteristic of diabetic glomerulosclerosis....

Hemoglobin Casts

This 58-year-old African American male without significant past medical history presents with fatigue and weakness. During workup, he was found to have anemia, mild thrombocytopenia, elevated LDH, low haptoglobin and acute kidney injury. The serum creatinine at presentation was 5.5 mg/dl. A renal biopsy was performed and shows acute tubular injury with numerous granular and globular eosinophilic (Fig 1) and fuchsinophilic casts (Fig 2) within the tubular lumens. A myoglobin immunoperoxidase stain is negative (not shown) and a hemoglobin stain is diffusely positive within the pigmented casts. Otherwise, the glomeruli and vessels appear normal, without evidence of microangiopathy. These findings...

Focal Segmental Glomerulosclerosis (FSGS), Tip Variant

This biopsy was performed on a 9-year-old female with no significant past medical history, who presents with nephrotic syndrome. The serum creatinine at the time of the biopsy was 0.7 mg/dl. The UPCR was 9.6 g/g. Serum albumin was 2.1 g/dl. Complement levels and ANA were normal/negative. The biopsy shows glomeruli with minimal mesangial matrix expansion and hypercellularity (Fig 1), in the absence of segmental glomerulosclerosis or proliferative lesions. Immunofluorescence was negative for IgA, IgG, IgM, C3, C1q and kappa and lambda light chains (not shown). Electron microscopy shows widespread blunting, widening and effacement of epithelial foot processes (Fig 2),...