Influence of rituximab therapy on hepatitis C virus RNA concentration in kidney-transplant patients

Renal lesions associated with monoclonal gammopathies of undetermined significance: clinical forms, mechanisms of development, approaches to treatment

The term «monoclonal gammopathies of undetermined significance» (MGUS) was introduced by R. Kyle in 1978 to designate the condition characterized by the presence ofsmall amounts ofM-protein in the serum. In some patients, such condition remains benign for a long time but predetermines for the development of multiple myeloma and other B-lymphocytic tumours. Also, it can provoke non-cancerous diseases due to the toxic action of monoclonal proteins (immunoglobulins and free light chains) on various organs, especially kidneys. MGUS-associated renal lesions include glomerulopathies with organized deposits, such as AL-amyloidosis (amyloid light chain of immunoglobulin), cryoglobulinic and immunotactoid glomerulonephritis, and with unorganized deposits (light chain deposition and proliferative forms of idiopathic glomerulonephritis. The available experimental data throw light on the possible mechanisms of renal lesions. We summarized the literature data and original observations to describe methods for differential diagnostics of MGUS-associated renal lesions including the highly sensitive test for free light chine identification (Freelite method) and principles of pathogenetic treatment by the impact on the pathological B-cell clone.

Hepatitis C virus associated glomerulopathies

Hepatitis C virus (HCV) infection is a systemic disorder which is often associated with a number of extrahepatic manifestations including glomerulopathies. Patients with HCV infection were found to have a higher risk of end-stage renal disease. HCV positivity has also been linked to lower graft and patient survivals after kidney transplantation. Various histological types of renal diseases are reported in association with HCV infection including membranoproliferative glomerulonephritis (MPGN), membranous nephropathy, focal segmental glomerulosclerosis, fibrillary glomerulonephritis, immunotactoid glomerulopathy, IgA nephropathy, renal thrombotic microangiopathy, vasculitic renal involvement and interstitial nephritis. The most common type of HCV associated glomerulopathy is type I MPGN associated with type II mixed cryoglobulinemia. Clinically, typical renal manifestations in HCV-infected patients include proteinuria, microscopic hematuria, hypertension, acute nephritis and nephrotic syndrome. Three approaches may be suggested for the treatment of HCV-associated glomerulopathies and cryoglobulinemic renal disease: (1) antiviral therapy to prevent the further direct damage of HCV on kidneys and synthesis of immune-complexes; (2) B-cell depletion therapy to prevent formation of immune-complexes and cryoglobulins; and (3) nonspecific immunosuppressive therapy targeting inflammatory cells to prevent the synthesis of immune-complexes and to treat cryoglobulin associated vasculitis. In patients with moderate proteinuria and stable renal functions, anti-HCV therapy is advised to be started as pegylated interferon-α plus ribavirin. However in patients with nephrotic-range proteinuria and/or progressive kidney injury and other serious extra-renal manifestations, immunosuppressive therapy with cyclophosphamide, rituximab, steroid pulses and plasmapheresis should be administrated.

Hepatitis C virus and kidney disease

Hepatitis C virus (HCV) is the most frequently observed viral infection in patients with kidney disease. HCV can cause glomerular disease, which can lead to end-stage renal disease that requires dialysis and/or kidney transplantation. It is recommended to test HCV patients once a year for proteinuria, microscopic hematuria and estimated glomerular filtration rate. Membranoproliferative glomerulonephritis is the most common glomerular disease induced by HCV. Over the past few decades, the prevalence of HCV infection has decreased among dialysis and kidney transplant patients. However, survival is significantly lower in HCV-positive than in HCV-negative dialysis patients whereas survival is significantly better in HCV-positive kidney transplant patients compared with HCV-positive dialysis patients. Thus, dialysis patients without a sustained virological response after anti-HCV therapy should be proposed for kidney transplantation. Recurrence or de novo occurrence of glomerular disease is responsible for the lower kidney allograft survival in HCV-positive compared with HCV-negative kidney transplant patients. Dialysis and kidney transplantation do not appear to negatively affect progression of liver fibrosis in the majority of patients. The available data also suggest that occult HCV infection does not exist in dialysis and kidney transplant patients.

Management of the kidney transplant patient with chronic hepatitis C infection

Chronic Hepatitis C (HCV) infection is an important cause of morbidity and mortality in patients with end-stage renal disease. Renal transplantation confers a survival advantage in HCV-infected patients. Renal transplant candidates with serologic evidence of HCV infection should undergo a liver biopsy to assess for fibrosis and cirrhosis. Patients with Metavir fibrosis score ≤3 and compensated cirrhosis should be evaluated for interferon-based therapy. Achievement of sustained virological response (SVR) may reduce the risks for both posttransplantation hepatic and extrahepatic complications such as de novo or recurrent glomerulonephritis associated with HCV. Patients who cannot achieve SVR and have no live kidney donor may be considered for HCV-positive kidneys. Interferon should be avoided after kidney transplant except for treatment of life-threatening liver injury, such as fibrosing cholestatic hepatitis. Early detection, prevention, and treatment of complications due to chronic HCV infection may improve the outcomes of kidney transplant recipients with chronic HCV infection.

Transplantation in the patient with hepatitis C

Hepatitis C virus (HCV) infection is the most frequent cause of liver disease after renal transplantation. Its clinical course is irrelevant in the short term, except for rare cases of fibrosing cholestatic hepatitis. However, in the long run, HCV infection can lead to major liver complications. Because interferon (IFN) is generally contraindicated in renal transplant patients, the best approach is to treat patients on dialysis. Until more information with pegylated-IFN is available, the use of alpha-IFN monotherapy is recommended. Most of the patients with sustained virological response remain HCV RNA negative after transplantation. HCV-positive renal transplant patients have a higher risk for proteinuria, chronic rejection, infections and post-transplant diabetes (PTDM). Long-term patient- and graft-survival rates are lower in HCV-positive patients. Mortality is higher, mainly as a result of liver disease and infections. HCV can contribute to the development of certain neoplasias such as post-transplant lymphoproliferative disease (PTLD). HCV infection is also an independent risk factor for graft loss. PTDM, transplant glomerulopathy and HCV-related glomerulonephritis can contribute to graft failure. Despite this, transplantation is the best option for end-stage renal disease in HCV-positive patients. Several measures to minimize the consequences of HCV infection have been recommended. Adjustment of immunosuppression and careful follow up in the outpatient clinic for early detection of HCV-related complications are mandatory.

Hepatitis C infection and chronic renal diseases

More than 170 million people worldwide are chronically infected with the hepatitis C virus (HCV), which is responsible for over 1 million deaths resulting from cirrhosis and liver cancers. Extrahepatic manifestations are also relevant and include mixed cryoglobulinemia, lymphoproliferative disorders, and kidney disease. HCV infection is both a cause and a complication of chronic kidney disease, occurring largely in the context of mixed cryoglobulinemia. This infection also represents a major medical and epidemiologic challenge in patients with end-stage renal disease on renal replacement therapy with dialysis or transplantation. In these settings the presence of HCV correlates with higher rates of patient mortality than in HCV-negative subjects on dialysis or undergoing kidney transplant. The major concern is the lack of safe and effective drugs to treat HCV-infected patients with chronic kidney disease. Unfortunately, there are no large-scale clinical trials in this population, especially those receiving renal replacement therapy, so that strong evidence for treatment recommendations is scant. This review article provides the readers with the most recent insights on HCV infection both as cause and complication of chronic kidney disease, discusses pitfalls and limitations of current therapies, and reports on preliminary experience with novel therapeutic agents, as well as directions for future research.