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The COVID-19 era has been a reminder to clinicians around the world of the important role that viral infections play in promoting glomerular disease. Several viral infections including human immunodeficiency virus (HIV), severe acute respiratory syndrome coronavirus 2, Epstein-Barr virus, cytomegalovirus, and parvovirus B19 can cause podocyte injury and present with a collapsing glomerulopathy (CG) variant of focal segmental glomerulosclerosis or minimal change disease. CG associated with COVID-19 has been termed COVID-19-associated nephropathy due to its striking resemblance to HIV-associated nephropathy. Host susceptibility is a major determinant of viral infection-associated CG, and the presence of two APOL1 risk variants explains most of the racial predilection to viral-associated CG observed in individuals of African ancestry. Interactions between APOL1 risk variants, viral genes, and the systemic inflammatory response to viral infection all contribute to kidney injury. This review will summarize our current knowledge of viral infection-associated CG, focusing primarily on the clinical presentation, histological features, mechanisms, and disease course of HIV-associated nephropathy and COVID-19-associated nephropathy., (Copyright © 2023 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Kidney injury is a well-known complication in people with coronavirus disease 2019 (COVID-19). In kidney transplant recipients with COVID-19, presentation with nephrotic syndrome has not been well described. We report on a 49-year-old black female kidney transplant recipient who presented 25 years after transplant with clinical features of nephrotic syndrome following a diagnosis of COVID-19. Histologic examination showed acute tubular injury with unremarkable glomeruli on light microscopy and diffuse foot process effacement of podocytes on electron microscopy, consistent with minimal change-like podocyte injury. Apolipoprotein L1 (APOL1) genetic testing confirmed 2 high-risk APOL1 alleles in the kidney donor. We speculate that COVID-19-induced systemic or local cytokine release could serve as a second hit in the presence of APOL1 risk alleles and mediate a podocytopathy manifesting as nephrotic syndrome. The presented case with minimal change-like disease, occurring in the context of the donor high-risk APOL1 genotype, extends the spectrum of clinical manifestations in COVID-19-associated nephropathy., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: The seroprevalence of human Parvovirus B19 (PVB19) is 70-85% in adults worldwide. PVB19 is the etiologic agent of the fifth disease, is a cause of aplastic anemia, and can be associated with kidney injury. We aimed to describe the cases of 4 patients with kidney injury related to PVB19 primary infection, and to evaluate the seroprevalence of PVB19 and the incidence of PVB19 primary infection in patients undergoing a native kidney biopsy., Methods: Cases of PVB19 infection with kidney injury were reviewed from the archives of the department of Nephrology. A systematic screening of anti-PVB19 IgG and IgM antibodies and viral DNA was performed in sera from 100 consecutive patients with a kidney biopsy in 2017-2018., Results: The 4 patients with PVB19 infection-associated kidney disease displayed: one lupus-like glomerulonephritis (GN) without lupus auto-antibodies, one minimal change disease with tubular necrosis, one secondary hemolytic and uremic syndrome and one membrano-proliferative GN. In the 100 patients biopsied, 67 had elevated anti-PVB19 IgG, among whom 8 had elevated IgM, without circulating viral DNA, without any particular renal pathological pattern. One additional patient showed a seroconversion at the time of kidney biopsy, which revealed a class V lupus nephritis., Conclusion: PVB19 primary infection can be associated with different kidney diseases. The seroprevalence of PVB19 among patients with a kidney biopsy is similar to the overall population, and primary infection is rarely documented (1%) after systematic screening. Whether PV19 is nephrotoxic, or triggers renal endothelial injury and immune activation, remains to be elucidated.

We report a case of relapse of minimal change disease following infection with the influenza A (H1N1) virus responsible for the 2009 pandemic. A 22-year-old man who had been diagnosed with minimal change disease presented with systemic edema. He had achieved complete remission with an oral steroid (prednisolone 1 mg/kg/day) by the 17th day of administration. On the 27th day of prednisolone administration, he presented with a new onset of generalized edema after several days of productive coughing. His urine showed proteinuria (4+) with a protein/creatinine ratio (PCR) of 2852.1 mg/g. His nasal swab sample was positive for the 2009 pandemic influenza (H1N1) virus by real-time reverse-transcriptase polymerase chain reaction (RT-PCR). He received oseltamivir (150 mg/day) for 5 days. A day after completing the oseltamivir therapy, his proteinuria returned to a normal range; urinalysis was negative for protein with PCR 79.2 mg/g. One month later, the patient remained normal with no proteinuria.

Background: Although hepatitis C virus (HCV) infection is known to be associated with Type 2 cryoglobulinemic glomerulopathy (CG), only a few reports about other types of nephropathy have been published., Methods: 68 HCV antibody positive patients in whom renal biopsy had been performed for persistent proteinuria, hematuria, and/or renal dysfunction between 1992 and 2008 at our institute were included. The histological, clinical and laboratory characteristics including the age, gender, hypertension, diabetes mellitus, liver histology (chronic hepatitis or liver cirrhosis), HCV-RNA, HCV genotype, splenomegaly, gastroesophageal varices, serum creatinine, hemoglobin, platelet count, rheumatoid factor, cryoglobulin, IgG, IgA, IgM, CH50, C3, C4, creatinine clearance, 24-h protein excretion, and hematuria, between their nephropathy with and without immune deposition were compared., Results: Nephropathy was classified into two groups based on the detection of immune deposits by immunofluorescence microscopy: i.e., a positive group (n = 39) and a negative group (n = 29). The former group was further classified into three types of nephropathy: IgG dominant group (n = 10) (including membranous nephropathy (MN)), IgA dominant group (n = 20) (including IgA nephropathy (IgAN)), membranoproliferative glomerulonephritis (MPGN) (IgA type)), and IgM dominant group (n = 9) (MPGN apart from the IgA type). The latter group included diabetic nephropathy (n = 13), focal glomerular sclerosis (n = 4), and benign nephrosclerosis (n = 3), malignant nephrosclerosis (n = 1), tubulointerstitial nephritis (TIN) (n = 2), minimal change nephrotic syndrome (n = 1), cast nephropathy (n = 1), granulomatous TIN (n = 1), and others (n = 3). An increased serum IgM level, hypocomplementemia, splenomegaly, thrombocytopenia, liver cirrhosis, hematuria, and a high HCV RNA level were features of patients with MPGN of IgM dominant group (consistent with "CG")., Conclusions: Our results showed various histological patterns of HCV-related kidney disease and the specificity of CG, and revealed that a minority of HCV patients (n = 7) presented typical CG, while IgAN, MN, and diabetic nephropathy were more frequent.

Recently, Epstein-Barr virus (EBV) received attention because a latent form of its infection in renal proximal tubular epithelial cells was found to cause idiopathic, chronic tubulointerstitial nephritis. In this report, we describe the case of a patient with a replicative form of EBV infection, chronic active EBV infection (CAEBV), who developed acute tubulointerstitial nephritis and minimal change nephrotic syndrome. A renal biopsy revealed papillary infoldings of atypical tubular epithelium and adjacent dense infiltration of lymphocytes. Using in situ polymerase chain reaction methods, we detected the EBV genome in some of the infiltrating lymphocytes, but not in the tubular epithelial cells. EBV-infected T cells are thought to activate other educated T cells, as well as secrete an unrestricted variety of cytokines, thus playing a pivotal role in CAEBV and its end organ disease. Therefore, in our case, the CAEBV activated, educated T cells may have followed the EBV-infected lymphocytes as they infiltrated into the peritubular interstitium, and promoted focal tubular epithelial atypia and minimal change nephrotic syndrome. The long-term observation of such patients is important because CAEBV may progress into lymphoproliferative diseases., (Copyright 2002 S. Karger AG, Basel)

Between December 1984 and November 1996, 171 children under 12 years old presented to the University Hospital of the West Indies with nephrotic syndrome. Hepatitis B surface antigen (HBsAg) was found in ten (6%) of these children, eight of whom had membranous nephropathy (MN), and one each had mesangial proliferative glomerulonephritis (MesN) and minimal change nephrotic syndrome (MCNS). Only those children with MesN and MCNS were steroid-sensitive. The HBsAg-positive status was identified incidentally on screening. At a mean follow-up of 34 months, seven of ten children had experienced complete or partial remission and three had persistent nephrotic syndrome, although none was in renal failure. Six of the ten had biochemical hepatitis. All the children were still HBsAg-positive. Hepatitis B virus (HBV) is a factor contributory to nephrotic syndrome in Jamaican children. As diagnostic clinical markers for HBV-associated nephropathy are usually absent, all children presenting with nephrotic syndrome should be screened for HBsAg. A policy should be implemented in Jamaica for screening pregnant women and at-risk groups for HBsAg, as well as for immunising susceptible neonates, in order to reduce the incidence of HBV-associated pathology.

Focal segmental glomerulosclerosis (FSGS) represents a clinicopathological syndrome with diverse causes. We examined the possibility that some cases of FSGS are associated with parvovirus B19 infection. We studied renal biopsy tissue from 40 patients, including those with idiopathic FSGS, collapsing FSGS, membranous nephropathy, and minimal change disease, as well as normal renal tissue removed at the time of nephrectomy from 4 patients. DNA was extracted from frozen blocks of kidney tissue and amplified using nested polymerase chain reaction. Parvovirus B19 DNA was amplified from 8 of 10 patients with idiopathic FSGS, 9 of 10 patients with collapsing FSGS, 6 of 10 patients with membranous nephropathy, 5 of 10 patients with minimal change disease, and 2 of 4 cancer nephrectomy samples. The prevalence of parvovirus B19 DNA was greater among patients with idiopathic FSGS and collapsing FSGS compared with patients with other diagnoses (P = 0.05). In situ hybridization studies using digoxigenin-labeled DNA probes failed to detect parvovirus B19 nucleic acid in any of the kidney tissue samples. These results suggest that parvovirus B19 DNA is commonly found in the kidneys of patients with a range of renal diagnoses, possibly representing latent DNA from past infection. The failure to localize parvovirus B19 nucleic acid within kidney argues against ongoing, high-level viral replication. Nevertheless, the increased prevalence of B19 DNA in patients with idiopathic FSGS and collapsing FSGS could indicate a pathogenic role for the virus in the cause of FSGS in certain patients.

This study aimed to investigate the relationship between the carrying of respiratory tract viruses and the quantitative change of urinary protein of the steroid-responsive and simple nephrotic syndrome (SRSNS), and to assess the function of respiratory tract viruses in the triggering of the SRSNS, 37 children with nephrotic syndrome underwent the examination of respiratory tract viruses (APAAP method) once a week when they were hospitalized from August 1997 to March 1998. Among them, 17 children had simple nephrotic syndrome and 10 had nephritic nephrosis. Moreover, 18 children with respiratory infection in the same season were chosen as the control and were subjected to the examination of respiratory tract viruses by the same method. In the cases of SRSNS, the percentage for the carrying of respiratory tract viruses increases obviously in the acme, the percentage for the carrying of respiratory tract viruses of SRSNS has close relationship with the quantity of urinary protein (P < 0.05). There is no difference between the constitution of the category of the viruses carried in the acme of SRSNS and that of the viruses in the control (P > 0.05). The most frequently detected respiratory tract viruses in the acme of SRSNS is RNA virus, and that in the control is the same (P > 0.05). In the acme of SRSNS, most children have no symptoms of respiratory infection although respiratory tract viruses were detected. In the SRSNS, the percentage for the carrying of respiratory tract viruses increases obviously in the acme, it has an important relationship with the quantitative change of urinary protein. The category of the respiratory tract viruses detected in the SRSNS has a relationship with the season, this may be the reason why the cases of SRSNS so easily happen and relapse in this season. RNA virus perhaps plays an important role in the triggering of this disease, including the respiratory tract viruses infection and the carrying of respiratory tract viruses without the symptom of respiratory infection.