Drug-induced glomerulopathies

Podocyte Disease Following Treatment with Intravenous Ibandronate in an Older Patient

Bisphosphonates are commonly used to treat osteoporosis. While renal toxicity is common with pamidronate and zoledronate, few ibandronate-related cases are reported. We describe a rare case of ibandronate-associated nephrotoxicity. An 88-year-old woman was admitted for edema. She had been receiving intravenous ibandronate treatment for postmenopausal osteoporosis and had no other diagnosed diseases. She was presented with proteinuria, hypoalbuminemia (1.9 g/dL), and an elevated serum creatinine level (1.8 mg/dL). Renal biopsy revealed podocyte disease, favoring a diagnosis of focal segmental glomerulosclerosis. She was treated with diuretics, tacrolimus, and fimasartan. Steroids were avoided due to severe osteoporosis. Three months later, the edema had subsided and the laboratory findings had improved (serum albumin 3.5 g/dL, serum creatinine 0.97 mg/dL). This case emphasizes the importance of careful monitoring of proteinuria and renal function during ibandronate treatment. In older adult patients, kidney biopsy and immunosuppressive treatment may be considered based on physical activity and underlying diseases.

Differentiating primary and secondary FSGS using non-invasive urine biomarkers

Background

Focal segmental glomerulosclerosis (FSGS) is divided into genetic, primary (p), uncertain cause, and secondary (s) forms. The subclasses differ in management and prognosis with differentiation often being challenging. We aimed to identify specific urine proteins/peptides discriminating between clinical and biopsy-proven pFSGS and sFSGS.

Methods

Sixty-three urine samples were collected in two different centers (19 pFSGS and 44 sFSGS) prior to biopsy. Samples were analysed using capillary electrophoresis-coupled mass spectrometry. For biomarker definition, datasets of age-/sex-matched normal controls (NC, n = 98) and patients with other chronic kidney diseases (CKDs, n = 100) were extracted from the urinary proteome database. Independent specificity assessment was performed in additional data of NC (n = 110) and CKD (n = 170).

Results

Proteomics data from patients with pFSGS were first compared to NC (n = 98). This resulted in 1179 biomarker (P < 0.05) candidates. Then, the pFSGS group was compared to sFSGS, and in a third step, pFSGS data were compared to data from different CKD etiologies (n = 100). Finally, 93 biomarkers were identified and combined in a classifier, pFSGS93. Total cross-validation of this classifier resulted in an area under the receiving operating curve of 0.95. The specificity investigated in an independent set of NC and CKD of other etiologies was 99.1% for NC and 94.7% for CKD, respectively. The defined biomarkers are largely fragments of different collagens (49%).

Conclusion

A urine peptide-based classifier that selectively detects pFSGS could be developed. Specificity of 95%-99% could be assessed in independent samples. Sensitivity must be confirmed in independent cohorts before routine clinical application.

Decade of optimizing therapy with direct-acting antiviral drugs and the changing profile of patients with chronic hepatitis C

Chronic infection with the hepatitis C virus (HCV) remains a major health problem affecting approximately 58 million people worldwide. In the era of interferon (IFN)-based regimens, patients particularly infected with genotypes 1 and 4 achieved a low response rate. The implementation of direct-acting antivirals changed the landscape of HCV treatment. The increase in effectiveness provided us with the hope of eliminating HCV as a significant public threat by 2030. In the following years, there was an observed improvement in the treatment of HCV with genotype-specific regimens and highly effective pangenotypic options that are the most recent stage of the revolution. The optimization of therapy was accompanied by changes in the patient profile from the beginning of the IFN-free era over time. Patients treated with antiviral therapies were younger in successive periods, less burdened with comorbidities and comedications, more frequently treatment-naïve and had less advanced liver disease. Before the IFN-free era, specific subpopulations such as patients with HCV/HIV coinfection, those with a history of previous treatment, patients with renal impairment or with cirrhosis had lower chances for a virologic response. Currently, these populations should no longer be considered difficult to treat. Despite the high effectiveness of HCV therapy, there is a small percentage of patients with treatment failure. However, they can be effectively retreated with pangenotypic rescue regimens.

Secondary Membranous Nephropathy. A Narrative Review

Membranous nephropathy (MN) is a common cause of proteinuria and nephrotic syndrome all over the world. It can be subdivided into primary and secondary forms. Primary form is an autoimmune disease clinically characterized by nephrotic syndrome and slow progression. It accounts for ~70% cases of MN. In the remaining cases MN may be secondary to well-defined causes, including infections, drugs, cancer, or autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), urticarial vasculitis, sarcoidosis, thyroiditis, Sjogren syndrome, systemic sclerosis, or ankylosing spondylitis. The clinical presentation is similar in primary and secondary MN. However, the outcome may be different, being often related to that of the original disease in secondary MN. Also, the treatment may be different, being targeted to the etiologic cause in secondary MN. Thus, the differential diagnosis between primary and secondary MN is critical and should be based not only on history and clinical features of the patient but also on immunofluorescence and electron microscopy analysis of renal biopsy as well as on the research of circulating antibodies. The identification of the pathologic events underlying a secondary MN is of paramount importance, since the eradication of the etiologic factors may be followed by remission or definitive cure of MN. In this review we report the main diseases and drugs responsible of secondary MN, the outcome and the pathogenesis of renal disease in different settings and the possible treatments.

Evaluation of podocin in urine in horses using qualitative and quantitative methods

No sensitive method for diagnosing early kidney dysfunction in horses has been identified so far. Many studies carried out in humans and small animals show that podocin can be useful to diagnose various kidney diseases, mainly affecting the glomeruli. The aim of this study was to perform a qualitative and quantitative analysis of podocin in urine samples obtained from healthy horses, horses with clinical kidney dysfunction and horses at risk of acute kidney injury. The study objectives aimed to assess: (1) whether the selected podocin tryptic peptide for LC-MS-MRM allows for podocin detection in horse; and (2) whether the species-specific ELISA test makes this detection possible as well;, (3) whether the chosen methods are sensitive enough to detect kidney dysfunction and glomerular injury, (4) whether the results of the tests applying both methods correspond with one another, (5) whether the results correlate with the hematological and biochemical data. The signals that may indicate the presence of trypsin fragments of podocin were found in three healthy horses, all the horses diagnosed with kidney dysfunction and half of the animals at risk for acute kidney injury. The concentration of podocin, diagnosed with the ELISA test was as follows: from 0.19 to 1.2 ng/ml in healthy animals, from 0.19 to 20.0 ng/ml in AKI horses, from 0.29 to 5.71 ng/ml in horses at risk for acute kidney injury. The results of both methods corresponded significantly. Podocin may be a potential biomarker of clinical kidney disease in horses and may be used in the detection of glomerular injury. However, its use is limited by the possibility of physiological podocyturia. LC-MS-MRM seems to be a more sensitive method to evaluate the presence of podocin than the ELISA test, whilst selected tryptic peptides of podocin appear to apply to horses. The ELISA test showed greater effectiveness in excluding the disease than in confirming it.

Differentiating Primary, Genetic, and Secondary FSGS in Adults: A Clinicopathologic Approach

FSGS describes a renal histologic lesion with diverse causes and pathogenicities that are linked by podocyte injury and depletion. Subclasses of FSGS include primary, genetic, and secondary forms, the latter comprising maladaptive, viral, and drug-induced FSGS. Despite sharing certain clinical and histologic features, these subclasses differ noticeably in management and prognosis. Without an accepted nongenetic biomarker that discriminates among these FSGS types, classification of patients is often challenging. This review summarizes the clinical and histologic features, including the onset and severity of proteinuria as well as the presence of nephrotic syndrome, that may aid in identifying the specific FSGS subtype. The FSGS lesion is characterized by segmental sclerosis and must be differentiated from nonspecific focal global glomerulosclerosis. No light microscopic features are pathognomonic for a particular FSGS subcategory. The characteristics of podocyte foot process effacement on electron microscopy, while helpful in discriminating between primary and maladaptive FSGS, may be of little utility in detecting genetic forms of FSGS. When FSGS cannot be classified by clinicopathologic assessment, genetic analysis should be offered. Next generation DNA sequencing enables cost-effective screening of multiple genes simultaneously, but determining the pathogenicity of a detected genetic variant may be challenging. A more systematic evaluation of patients, as suggested herein, will likely improve therapeutic outcomes and the design of future trials in FSGS.

Anti-hepatitis C virus drugs and kidney

Hepatitis C virus (HCV) mainly targets the liver but can also induce extrahepatic manifestations. The kidney may be impacted via an immune mediated mechanism or a cytopathic effect. HCV patients are clearly at a greater risk of chronic kidney disease (CKD) than uninfected patients are, and the presence of CKD increases mortality. Interferon-based therapies and ribavirin are difficult to manage and are poorly effective in end-stage renal disease and hemodialysis. These patients should be given priority treatment with new direct anti-viral agents (DAAs) while avoiding peginterferon and ribavirin. The first results were convincing. To aid in the correct use of these drugs in patients with renal insufficiency, their pharmacokinetic properties and potential renal toxicity must be known. The renal toxicity of these new drugs was not a safety signal in clinical trials, and the drugs are generally efficient in these frail populations. These drugs are usually well tolerated, but recent cohort studies have demonstrated that these new regimens may be associated with renal side effects, especially when using sofosbuvir combinations. HCV, renal diseases and comorbidities are intimately linked. The close monitoring of renal function is required, particularly for at-risk patients (transplanted, HIV-coinfected, CKD, hypertensive or diabetic patients). New DAA regimens, which will soon be approved, will probably change the landscape.

Drug-induced glomerular disease: attention required!

Drugs and toxins frequently are associated with the development of various types of acute kidney disease and CKD. Although medications are a widely known cause of tubulointerstitial damage, drug-related glomerular injury is not well appreciated but nonetheless, important. Glomerular damage that occurs after exposure to medications can be caused by direct cellular injury involving the mesangial, endothelial, or visceral epithelial cells (podocytes). Examples include nodular glomerulosclerosis associated with smoking and endothelial injury with thrombotic microangiopathy from a number of medications. Podocyte injury with the development of a minimal change or FSGS lesion has also been described with various medications. Glomerulopathies may also be associated with drug-induced immune-mediated processes. Through various pathways, drugs may promote the formation of a number of antibodies, which may, ultimately, affect the glomerulus. Examples include lupus-like renal lesions and ANCA-related pauci-immune vasculitis. It is critical to recognize these conditions early, because in many patients, there is improvement in renal parameters on stopping the offending medication.

eGFR decrease during antiviral C therapy with first generation protease inhibitors: a clinical significance?

BACKGROUND & AIMS

Renal toxicity of first generation protease inhibitors (PIs) was not a safety signal in phase III clinical trials, but was recently reported in recent studies. It appeared important to determine the clinical significance of these findings.

METHODS

We retrospectively analysed 101 HCV patients receiving triple therapy with telaprevir (n = 36) or boceprevir (n = 26) or double therapy (n = 39) with peginterferon and ribavirin and having a close monitoring of eGFR (MDRD formula) during and after treatment. EGFR decline over time was assessed by a linear mixed-effects model (LMEM) with search for possible explanatory covariates.

RESULTS

Patients treated with telaprevir presented a significant decrease of eGFR with the same kinetics: initial decrease at W (week) 4, nadir at W8 (mean decrease 17.0 ± 18.9 ml/min/1.73 m(2)) and return to baseline at W16. The W8 eGFR was correlated with the D0 eGFR (R(2) = 0.49). The LMEM showed that interindividual variability in the slope of eGFR vs time between D0 and W8 was non-significant and eGFR nadir could be predicted from eGFR obtained at D0. In multivariate analysis, eGFR intercept (i.e. baseline value) was associated with older age and male sex.

CONCLUSION

The eGFR significantly varied in telaprevir group only. Our model showed that eGFR nadir mainly depended on initial eGFR. As telaprevir has been shown to inhibit mostly the drug transporter OCT2 which interacts with creatinine transport, the early decrease of eGFR observed could be a benign phenomenon. However, as unpredictable true renal toxicity may occur during therapy, we recommend a thorough follow-up of eGFR.

[Nephrotic syndrome in multiple sclerosis patients who had undergone long-term interferon β-1b therapy]

A 59-year-old man (case 1) with multiple sclerosis (MS) presented with shortness of breath and general fatigue. He had been treated using interferon β-1b (IFNβ-1b) since he was 51 years of age. Laboratory test results showed hypoproteinemia and hypoalbuminemia, proteinuria, and absence of hematuria. He was diagnosed with nephrotic syndrome, and the administration of IFNβ-1b was stopped. Percutaneous renal biopsy was performed, and the histology revealed membranous nephropathy. A 33-year-old woman (case 2) with MS, who had been treated using IFNβ-1b for 7 years, was diagnosed with proteinuria during a medical checkup. She was referred to a nephrologist and was found to have hypoalbuminemia and proteinuria. A diagnosis of nephrotic syndrome was made, and IFNβ-1b therapy was stopped. The patient underwent percutaneous renal biopsy, and the histology revealed membranous nephropathy. Both patients were treated using intravenous methylprednisolone followed by oral prednisolone. Case 1 was administered ciclosporin orally, and his clinical symptoms and laboratory test results improved at first, but his laboratory test results subsequently showed recurrence of proteinuria. Case 2 was administered mizoribine orally, resulting in improvement in clinical symptoms and laboratory test results. Case 2 showed relapse of multiple sclerosis, but the symptoms were mild and were alleviated after steroid therapy. IFNβ therapy has several complications including nephropathy. Previously, several cases of nephrotic syndrome associated with IFNβ within 2 years of therapy were reported, but drug-induced nephropathy could appear after several years of the therapy as our cases. We should pay attention to nephrotic syndrome under using long-term IFNβ.

Mechanisms of drug-induced nephrotoxicity

Drug-induced nephrotoxicity is a common complication of several medications and diagnostic agents. It is seen in both inpatient and outpatient settings with variable presentations ranging from mild, reversible injury to advanced kidney disease. Manifestations of drug-induced nephrotoxicity include acid-base abnormalities, electrolyte imbalances, urine sediment abnormalities, proteinuria, pyuria, hematuria, and, most commonly, a decline in the glomerular filtration rate. The mechanisms of drug-induced nephrotoxicity may differ between various drugs or drug classes, and they are generally categorized based on the histological component of the kidney that is affected. Aminoglycoside antibiotics, radiocontrast media, conventional nonselective nonsteroidal anti-inflammatory drugs, and selective cyclooxygenase-2 inhibitors, amphotericin B, and angiotensin-converting enzyme inhibitors have been frequently implicated. This chapter reviews the clinical presentation and basic mechanisms of drug-induced nephrotoxicity.

Collapsing glomerulopathy as a complication of interferon therapy for hepatitis C infection

We present the case of a patient with chronic hepatitis C and diabetes, who rapidly progressed to end stage renal disease upon initiation of IFNalpha therapy for his HCV infection. A kidney biopsy revealed advanced collapsing glomerulopathy.

De novo nephrotic syndrome following pegylated interferon alfa 2b/ribavirin therapy for chronic hepatitis C infection

This paper describes the case of a patient with HCV, without previous evidence of nephropathy, who following two well-tolerated cycles of treatment with interferon alone developed nephrotic syndrome after a third attempt with ribavirin associated with peginterferon alfa 2b. The patient exhibited a total remission when the antiviral treatment was discontinued.

Immunologic principles of allergic disease

Allergy either results from a pathological excessive immune reaction, or from the defective induction of tolerance to otherwise harmless antigens. Allergic reactions are mounted by mechanisms of innate and adaptive immunity. The development of an allergic response can be divided in sensitization and elicitation phases. Immediate type allergic reactions (e.g. anaphylaxis, urticaria, rhinoconjunctivitis allergica, allergic asthma) are mediated by IgE antibodies which are produced by B cells stimulated by allergen-specific Th2 cells. Crosslinking of allergen-specific IgE on membrane surfaces of mast cells and basophilic granulocytes leads to release of soluble mediators which may cause systemic symptoms within minutes to hours. The following infiltration of eosinophilic granulocytes and Th2 cells directs chronic inflammation. Humoral cytotoxic immune reactions (e.g. drug induced cytopenia) are mediated by IgG and IgM antibodies which are directed against membrane associated antigens. IgG and IgM antibodies directed against soluble antigens elicit immune complex mediated cytotoxicity (e.g.drug induced vasculitis). Delayed type immune reactions (e.g.contact dermatitis) are based on the activation of antigen specific CD4(+) and CD8(+) T cells and need 24 h to 48 h to develop. Upon recurrent contact with identical antigens, recruitment of CD4(+) and CD8(+) T cells cause inflammation and cytotoxic induced apoptosis in target cells as well as cytokine mediated leukocyte infiltration. Subsequent immigration of CD4(+) Th2 cells provides anti-inflammatory mechanisms leading to resolution of the inflammatory response and tissue repair.

Lack of effect of DX-619, a novel des-fluoro(6)-quinolone, on glomerular filtration rate measured by serum clearance of cold iohexol

DX-619 is a novel des-fluoro(6)-quinolone with activity against a broad range of bacterial strains, including methicillin-resistant Staphylococcus aureus. The effects of DX-619 on the glomerular filtration rate (GFR) were evaluated because drug-related increases in serum creatinine levels were observed in studies with healthy volunteers. Forty-one healthy subjects were randomized to receive intravenous DX-619 at 800 mg or placebo once daily for 4 days, and the GFR was directly measured by determination of the clearance of a bolus iohexol injection in 33 subjects who completed the study per protocol. DX-619 was noninferior to placebo for the GFR on the basis of a criterion for a clinically significant difference of -12 ml/min/1.73 m(2). The mean GFRs on day 4 were 101.1 +/- 14.2 ml/min/1.73 m(2) and 100.2 +/- 15.6 ml/min/1.73 m(2) for the volunteers receiving placebo and DX-619, respectively. On day 4 the mean serum creatinine concentration for volunteers receiving DX-619 increased by 30 to 40%, with a corresponding decrease in mean creatinine clearance. Both parameters normalized within 7 days after the cessation of DX-619 treatment. Nonclinical studies suggest that DX-619 increases the serum creatinine concentration by inhibiting excretory tubular transporters. In conclusion, DX-619 administered intravenously at 800 mg once a day for 4 days did not affect the GFR in healthy volunteers. Glomerular toxicity is not expected to present a risk to patients receiving DX-619 in clinical trials, but monitoring of the renal function, with an emphasis on the serum creatinine concentration, is still warranted.