Giant Cell Tubulitis with Tubular Basement Membrane Immune Deposits: A Report of Two Cases after Cardiac Valve Replacement Surgery

IgG4-related kidney disease: Clinicopathologic features, differential diagnosis, and mimics

IgG4-related kidney disease (IgG4-RKD) encompasses all forms of kidney disease that are part of IgG4-related disease (IgG4-RD). First recognized as IgG4-related tubulointerstitial nephritis (IgG4-TIN), and then IgG4-related membranous glomerulonephritis (IgG4-MGN), we now recognize additional patterns of interstitial nephritis, glomerular disease, and vascular disease that can be seen as part of IgG4-RKD. The clinical presentation is variable and can include acute or chronic kidney injury, proteinuria or nephrotic syndrome, mass lesion(s), and obstruction. While usually associated with other organ involvement by IgG4-RD, kidney-alone involvement is present in approximately 20 % of IgG4-RKD. Compared to IgG4-RD overall, patients with IgG4-RKD are more likely to show increased serum IgG4 or IgG, and more likely to have hypocomplementemia. In this review, we extensively cover other types of autoimmune and plasma cell-rich interstitial nephritis, mass forming inflammatory diseases of the kidney, and other mimics of IgG4-TIN, in particular ANCA-associated disease.

Red-Colored Urine in the Cardiac Surgical Patient-Diagnosis, Causes, and Management

Red-colored urine occurring in the intraoperative and early postoperative periods after cardiac surgery is often a cause for concern. This observation may be a result of hematuria from pathology within the urinary tract, anticoagulant-related nephropathy, drug-induced acute interstitial nephropathy, excretion of heme pigment-containing proteins, such as myoglobin and hemoglobin, and hemolysis occurring during extracorporeal circulation. Within the kidneys, heme-containing compounds result in pigment nephropathy, which is a significant contributory factor to cardiac surgery-associated acute kidney injury. Concerted efforts to reduce red blood cell damage during cardiopulmonary bypass, together with early recognition of the at-risk patient and the institution of prompt therapeutic intervention, may improve outcomes. This review addresses the diagnosis, causes, and management of red-discolored urine occurring during and after cardiac surgery.

Anti-LRP2 Nephropathy With Abundant IgG4-Positive Plasma Cells: A Case Report

In older adults, the most common kidney biopsy diagnoses include pauci-immune crescentic glomerulonephritis, membranous nephropathy, and focal segmental glomerulosclerosis. Recently, investigators described a small series of older patients (aged 66-80 years) with acute kidney injury and a kidney biopsy demonstrating tubular basement membrane (TBM) immune deposits of polytypic immunoglobulin G (IgG) and C3, acute tubular injury, and tubulointerstitial inflammation. They identified a circulating antibody against kidney tubular low-density lipoprotein (LDL) receptor-related protein 2 (LRP2; also known as megalin) in patients' sera and colocalization of LRP2 with IgG in TBM deposits. We present a rare case of anti-LRP2 nephropathy/anti-brush border antibody disease and describe the novel feature of abundant IgG4-positive interstitial plasma cells. Along with the combination of TBM deposits, tubulointerstitial nephritis (TIN), and segmental glomerular subepithelial immune deposits seen in both entities, this newly described feature adds to the morphologic overlap with IgG4-related TIN. Identification of large TBM deposits using light microscopy and IgG staining of apical aspects of proximal tubules using immunofluorescence microscopy can point to the correct diagnosis of anti-LRP2 nephropathy and prompt confirmatory studies. Particularly in older patients with immune complex-mediated TIN who lack clinical, laboratory, radiographic, and/or characteristic histologic features of IgG4-TIN or other autoimmune, infectious, or drug-related injury, a diagnosis of anti-LRP2 nephropathy should be considered.

Immune Complex Tubulointerstitial Nephritis Due to Autoantibodies to the Proximal Tubule Brush Border

Immune complex tubulointerstitial nephritis due to antibodies to brush border antigens of the proximal tubule has been demonstrated experimentally and rarely in humans. Our patient developed ESRD and early recurrence after transplantation. IgG and C3 deposits were conspicuous in the tubular basement membrane of proximal tubules, corresponding to deposits observed by electron microscopy. Rare subepithelial deposits were found in the glomeruli. The patient had no evidence of SLE and had normal complement levels. Serum samples from the patient reacted with the brush border of normal human kidney, in contrast with the negative results with 20 control serum samples. Preliminary characterization of the brush border target antigen excluded megalin, CD10, and maltase. We postulate that antibodies to brush border antigens cause direct epithelial injury, accumulate in the tubular basement membrane, and elicit an interstitial inflammatory response.

Giant cell tubulitis with immune complex deposits in a patient with lupus nephritis

We report a case of acute tubulointerstitial nephritis with giant cell tubulitis and tubular basement membrane immune complex deposits in a patient with membranous lupus nephritis. The patient, who had no prior evidence of lupus nephritis, developed acute kidney failure and mild proteinuria after cardiac valve replacement surgery. Giant cell tubulitis with tubular basement membrane immune complex deposits has been described in 4 patients after cardiac surgery, 3 of whom received cefuroxime, suggesting the possibility of a drug hypersensitivity reaction. The present case suggests there may also be a pathogenetic role for autoimmunity in this condition.

Spectrum of renal pathology in hematopoietic cell transplantation: a series of 20 patients and review of the literature

BACKGROUND AND OBJECTIVES

Hematopoietic cell transplantation is a common treatment option for a variety of hematopoietic malignancies. As a result of the use of total body irradiation and/or chemotherapeutic agents, renal dysfunction often ensues. Many pharmacologic agents, such as cyclosporine and high-intensity conditioning regimens, have been linked with thrombotic microangiopathy. In addition, an association between membranous nephropathy and graft-versus-host disease has been reported in this clinical setting.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

A study of autologous and allogeneic hematopoietic cell transplantation patients with renal dysfunction was conducted to document the spectrum of renal manifestations. The pathology files at the University of Washington and University of Chicago Medical Centers were reviewed, and 20 patients with a kidney biopsy after hematopoietic cell transplantation were identified. The histologic findings were correlated with relevant clinical information.

RESULTS

A wide spectrum of renal diseases could be classified into four categories: (1) Complications related to hematopoietic cell transplantation (conditioning regimen, immunosuppression, or posttransplantation complications), (2) podocytopathy, (3) membranous nephropathy, or (4) recurrence or persistence of original hematologic disease. Pathologic diagnoses included thrombotic microangiopathy, polyoma virus nephropathy, acute kidney injury/acute tubular necrosis, acute and chronic interstitial nephritis, minimal-change disease, "tip" variant of focal segmental glomerulosclerosis, membranous nephropathy, amyloidosis, and myeloma cast nephropathy. Membranous nephropathy, minimal-change disease, and amyloidosis were common causes of severe proteinuria. Because of the conditioning regimens, posttransplantation complications, and potential nephrotoxic agents used during hematopoietic cell transplantation, it was difficult to attribute the subsequent renal dysfunction to specific factors.

CONCLUSIONS

The renal biopsy remains essential for diagnosing the underlying injury that can affect one or more compartments of the kidney in this unique clinical setting.