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Recent case reports suggest that coronavirus disease 2019 (COVID-19) is associated with collapsing glomerulopathy in African Americans with apolipoprotein L1 gene (APOL1) risk alleles; however, it is unclear whether disease pathogenesis is similar to HIV-associated nephropathy. RNA sequencing analysis of a kidney biopsy specimen from a patient with COVID-19–associated collapsing glomerulopathy and APOL1 risk alleles (G1/G1) revealed similar levels of APOL1 and angiotensin-converting enzyme 2 (ACE2) messenger RNA transcripts as compared with 12 control kidney samples downloaded from the GTEx (Genotype-Tissue Expression) Portal. Whole-genome sequencing of the COVID-19–associated collapsing glomerulopathy kidney sample identified 4 indel gene variants, 3 of which are of unknown significance with respect to chronic kidney disease and/or focal segmental glomerulosclerosis. Molecular profiling of the kidney demonstrated activation of COVID-19–associated cell injury pathways such as inflammation and coagulation. Evidence for direct severe acute respiratory syndrome coronavirus 2 infection of kidney cells was lacking, which is consistent with the findings of several recent studies. Interestingly, immunostaining of kidney biopsy sections revealed increased expression of phospho-STAT3 (signal transducer and activator of transcription 3) in both COVID-19–associated collapsing glomerulopathy and HIV-associated nephropathy as compared with control kidney tissue. Importantly, interleukin 6–induced activation of STAT3 may be a targetable mechanism driving COVID-19–associated acute kidney injury.

Malaria remains a important global disease with more than 200 million cases and 600 000 deaths each year. Malaria-associated acute kidney injury (MAKI) may occur in up to 40% of patients with severe malaria and is associated with increased mortality. Histopathological characteristics of AKI in malaria are acute tubular injury, interstitial nephritis, focal segmental glomerulosclerosis, collapsing glomerulopathy and glomerulonephritis. We observed that C57BL/6 mice infected with Plasmodium berghei NK65 (PbNK65) develop MAKI in parallel with malaria-associated acute respiratory distress syndrome (MA-ARDS). MAKI pathology was associated with proteinuria, acute tubular injury and collapse of glomerular capillary tufts, which resolved rapidly after treatment with antimalarial drugs. Importantly, parasite sequestration was not detected in the kidneys in this model. Furthermore, with the use of skeleton binding protein-1 (SBP-1) KO PbNK65 parasites, we found that parasite sequestration in other organs and its subsequent high parasite load are not required for the development of experimental MAKI. Similar proteinuria, histopathological features, and increases in kidney expression of interferon-γ, TNF-α, kidney injury molecule-1 (KIM-1) and heme oxygenase-1 (HO-1) was observed in both infected groups despite a significant difference in parasite load. Taken together, we introduce a model of experimental AKI in malaria with important similarities to AKI in malaria patients. Therefore, this mouse model might be important to further study the pathogenesis of AKI in malaria. ispartof: FRONTIERS IN CELLULAR AND INFECTION MICROBIOLOGY vol:12 ispartof: location:Switzerland status: published

Background Coronavirus disease-2019 (COVID-19) is an ongoing pandemic which has affected over 12 million people across the globe. Manifestations in different organs systems are being reported regularly. Renal biopsy findings in hospitalized COVID-19 patients presenting solely with acute kidney injury (AKI) have recently been described in published literature in few case reports. The findings include diffuse acute tubular injury (ATI) along with the glomerular lesion of collapsing glomerulopathy (CG). However, nephrotic syndrome as the presenting complaint of COVID-19 has not been reported widely, neither has any other glomerular lesion other than CG. Case presentation We describe the kidney biopsy findings of two patients who had recent diagnoses of COVID-19 and presented with new-onset nephrotic syndrome. Renal biopsy in both patients showed ATI (as in previous reports) and distinct glomerular findings on light microscopy – that of minimal change disease (MCD) initially in one patient followed by CG in a subsequent biopsy and CG at the outset in the other patient. The electron microscopic findings in both patients were that of severe podocytopathy (diffuse and severe podocyte foot process effacement). Conclusion Our cases highlight a novel clinical presentation of COVID-19 renal disease, not described before, that of new-onset nephrotic syndrome. While all published case reports describe CG as the glomerular pathology, we describe a non-CG pathology (MCD) in one of our cases, thereby adding to the repertoire of renal pathology described in association with COVID-19 patients. However, the exact mechanism by which podocyte injury or podocytopathy occurs in all such cases is still unknown. Optimal treatment options for these patients also remains unknown at this time.

Among patients hospitalized for novel coronavirus disease (COVID-19), between 10 and 14% develop an acute kidney injury and around half display marked proteinuria and haematuria. Post-mortem analyses of COVID-19 kidney tissue suggest that renal tubular cells and podocytes are affected. Here we report two cases of collapsing glomerulopathy and tubulointerstitial lesions in living COVID-19 patients. Despite our use of sensitive reverse transcription polymerase chain reaction techniques in this study, we failed to detect the virus in blood, urine and kidney tissues. Our observations suggest that these kidney lesions are probably not due to direct infection of the kidney by severe acute respiratory syndrome coronavirus 2.

Coronavirus Disease 2019 (COVID-19) has posed unique challenges to nephrology. COVID-19–associated acute kidney injury occurs in as high as 36.6% of patients,S1 with the most common etiology being acute tubular injury due to hemodynamic changes and a proinflammatory milieu. In addition to acute tubular injury, patients with COVID-19 can also develop a variety of glomerular pathologies, including primary podocytopathies and immune-mediated glomerular diseases (membranous nephropathy, lupus nephritis, anti–glomerular basement membrane disease).1 Here, we report another pattern of tubular pathology related to COVID-19, osmotic injury associated with antiviral therapy.

Introduction/Objective Collapsing glomerulopathy (CGN) mainly occurs in patients of African descent because a majority of these patients have APOL-1 gene mutations that results in damage of terminally differentiated podocytes, diffuse fusion of foot processes, and podocyte hyperplasia. Idiopathic FSGS is associated with high rates of recurrent FSGS in renal transplants and can be seen in patients with APOL-1 gene mutations as well, but recurrent FSGS progressing to CGN is not reported. Here we report an autopsy case with renal transplant showing recurrent FSGS progressing to CGN. Methods/Case Report Our patient was a 32 year old African American man who had a native renal biopsy which showed primary FSGS (with no infectious history) 8 years ago. Last year he received a renal transplantation (complex donor kidney from a deceased 25 year old man with pre-mortem serum creatinine (sCr) at 0.7 mg/dl). His initial post- transplant sCr level was as low as 1.17 mg/dl. However, in 4 months his sCr went up and he began to have higher levels of proteinuria. Sequential biopsies indicated that the patient developed a recurrent FSGS that progressed to show features of CGN. In his autopsy kidney graft, approximately 50% of glomeruli show collapsed loops with various degrees of hyperplasic podocytes, confirmed by positive CD133 staining (a progenitor cell marker). In addition, the hyperplastic podocytes lost WT-1 expression and were positive for Ki-67 staining. Distal tubules showed obvious cystic dilation. Overall findings were consistent with a severe form of CGN. Results (if a Case Study enter NA) NA Conclusion The clinical presentation of recurrent FSGS progressing to collapsing FSGS in our patient suggests that CGN and idiopathic FSGS may share a common pathophysiologic mechanism of disease.

Acute kidney injury (AKI) is common among hospitalized patients with coronavirus disease 2019 (COVID-19), with the occurrence of AKI ranging from 0.5% to 80%. An improved knowledge of the pathology of AKI in COVID-19 is crucial to mitigate and manage AKI and to improve the survival of patients who develop AKI during COVID-19. In this review, we summarize the published cases and case series of various kidney pathologies seen with COVID-19. Both live kidney biopsies and autopsy series suggest acute tubular injury as the most commonly encountered pathology. Collapsing glomerulopathy and thrombotic microangiopathy are other encountered pathologies noted in both live and autopsy tissues. Other rare findings such as anti-neutrophil cytoplasmic antibody vasculitis, anti-glomerular basement membrane disease and podocytopathies have been reported. Although direct viral infection of the kidney is possible, it is certainly not a common or even widespread finding reported at the time of this writing (November 2020).

Kidney involvement appears to be frequent in coronavirus disease 2019 (COVID-19). Despite this, information concerning renal involvement in COVID-19 is still scarce. Several mechanisms appear to be involved in the complex relationship between the virus and the kidney. Also, different morphological patterns have been described in the kidneys of patients with COVID-19. For some authors, however, this association may be just a coincidence. To investigate this issue, we propose assessing renal morphology associated with COVID-19 at the renal pathology reference center of federal university hospitals in Brazil. Data will come from a consortium involving 17 federal university hospitals belonging to Empresa Brasileira de Serviços Hospitalares (EBSERH) network, as well as some state hospitals and an autopsy center. All biopsies will be sent to the referral center for renal pathology of the EBSERH network. The data will include patients who had coronavirus disease, both alive and deceased, with or without pre-existing kidney disease. Kidney biopsies will be analyzed by light, fluorescence, and electron microscopy. Furthermore, immunohistochemical (IHC) staining for various inflammatory cells (i.e., cells expressing CD3, CD20, CD4, CD8, CD138, CD68, and CD57) as well as angiotensin-converting enzyme 2 (ACE2) will be performed on paraffinized tissue sections. In addition to ultrastructural assays, in situ hybridization (ISH), IHC and reverse transcription-polymerase chain reaction (RT-PCR) will be used to detect Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) in renal tissue. For the patients diagnosed with Collapsing Glomerulopathy, peripheral blood will be collected for apolipoprotein L-1 (APOL1) genotyping. For patients with thrombotic microangiopathy, thrombospondin type 1 motif, member 13 (ADAMTS13), antiphospholipid, and complement panel will be performed. The setting of this study is Brazil, which is second behind the United States in highest confirmed cases and deaths. With this complete approach, we hope to help define the spectrum and impact, whether immediate or long-term, of kidney injury caused by SARS-CoV-2.

Collapsing glomerulopathy is a distinct and aggressive clinicopathologic variant of focal segmental glomerulosclerosis (FSGS). Here we present a 46-year-old man with acute renal failure from biopsy-proven collapsing FSGS and nephrotic syndrome in the setting of a diagnosis of hemophagocytic lymphohistiocytosis secondary to acute Epstein-Barr virus infection. This rare association has not been well described previously.

Background and Aims Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome induced by aberrantly activated macrophages and cytotoxic T cells. The primary (genetic) form, caused by mutations affecting lymphocyte cytotoxicity and immune regulation, is most common in children, whereas the secondary (acquired) form is most frequent in adults. Secondary HLH is commonly triggered by infections or malignancies but may also be induced by autoinflammatory/autoimmune disorders, in which case it is called macrophage activation syndrome. The diagnosis of HLH in adults should be based on the HLH-2004 diagnostic criteria in conjunction with clinical judgment and the patient’s history. Renal involvement has previously been reported in 24 adult cases, mostly as acute renal failure. Collapsing glomerulopathy is extremely rare with only six previous cases reported in the literature. Case presentation We report the case of an African man, 31 years old, presented with fever, acute kidney injury: serum creatinine 10.3 mg/dl; urine protein 600 mg/dl, macrohematuria, ANA/ANCA were negative, low serum C3, organomegaly, anemia, thrombocytopenia, hypertriglyceridemia, hypofibrinogenemia, hyperferritinemia, direct and indirect antiglobulin (Coombs) tests were negative, low haptoglobin; elevated LDH; normal partial thromboplatin time. Peripheral blood smear examination reveal few schistocytes. ADAMTS13 activity was found to be 25%. HBV-DNA and HIV were negative. Anticardiolipin antibodies were negative. Lab exam suggested the relapse of an EBV infection and primary mycoplasma infection. Because of uremic symptoms and persisting oliguria we started replacement therapy by hemodialysis. Plasmapheresis was started because of suspected thrombotic microangiopathy. Suprisingly the kidney biopsy was consistent with collapsing glomerulopathy with evidence of tubular injury while the bone marrow biopsy diagnosed an EBV NK/T-Cell lymphoma. During the course of his hospitalization, the patient suffered high fever. C-reactive protein, WBC and procalcitonin levels were elevated. Antimicrobial agents were initiated, starting with ceftriaxone then upgraded to piperacillin/tazobactam and then the shifted to teicoplanin and meropenem. Blood, urine and stool cultures were negative.VRE positive, IgM Mycoplasma pneumoniae were positive; EBV PCR on bone marrow blood was positive. Malaria screening was negative. The antibiotic therapy was finally switched to doxycycline as unique agent. Steroid therapy (dexamethasone daily 40 mg) and IVIG (daily 35g) were initiated then these drug were stopped. CHOP-like regimen ( Etoposide 75 mg/m2, twice a week for two weeks then once a week until the seventh week) and Rituximab (375 mg/m2, once a week for 4 weeks) were initiated and continued for two weeks. Later on the patient died because of sepsis and multi-organ failure. Conclusions The multidisciplinary approach is very important. Physicians should be aware of HLH, because early recognition may prevent irreversible organ damage and subsequent death.4,5 In adults, HLH-associated mortality remains high, especially in patients with underlying malignancies. Collapsing glomerulopathy is the most commonly reported finding on renal biopsy. Renal prognosis appears to be poor with most patients remaining dialysis-dependent. The increased awareness of HLH, together with a more rapid diagnostic workup and new therapeutic approaches, will improve the prognosis of HLH in adults.

International audience; We report a case of a kidney transplant recipient who presented with acute kidney injury and nephrotic-range proteinuria in a context of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Kidney biopsy revealed collapsing glomerulopathy. Droplet-based digital polymerase chain reaction did not detect the presence of SARS-CoV-2 RNA in the biopsy fragment, and the virus was barely detectable in plasma at the time of the biopsy. SARS-CoV-2 RNAemia peaked several days later, followed by a seroconversion despite the absence of circulating CD19-positive lymphocytes at admission due to rituximab-based treatment of antibody-mediated rejection 3 months earlier. Genotyping for the 2 risk alleles of the apolipoprotein L1 (APOL1) gene revealed that the donor carried the low-risk G0/G2 genotype. This case illustrates that coronavirus disease 2019 infection may promote a collapsing glomerulopathy in kidney allografts with a low-risk APOL1 genotype in the absence of detectable SARS-CoV-2 RNA in the kidney and that podocyte injury may precede SARS-CoV-2 RNAemia.

Hydrophilic polymer is a synthetic, biodegradable coating applied to various intravascular devices and vascular grafts to reduce friction between instruments and endothelium, in an effort to prevent vasospasm and thrombosis.1, 2 However, the hydrophilic polymer itself can dislodge from these devices resulting in downstream ischemic complications involving brain, heart, lungs, kidneys, gastrointestinal tract, or skin.1, 2, 3, 4, 5, 6, 7, 8, 9,S1–S9 To date, 3 cases of hydrophilic polymer emboli have been reported to involve the kidneys, but none has been associated with collapsing glomerulopathy.4,S1,S6 Here, we report the first case of collapsing glomerulopathy temporally related to renal embolization by hydrophilic polymer.

Collapsing glomerulopathy (CGP) is a pattern of kidney injury seen on renal biopsy with multiple associations and etiologies. It is most commonly described in African-Americans and others with recent African ancestry. The disease is rapidly progressive and often presents with abrupt onset of renal failure and nephrotic-range proteinuria. Since its description 30 years ago, this entity has transformed from a morphologic diagnosis typically seen in the setting of HIV infection to a complicated diagnosis with numerous etiologies, many of which are associated with underlying apolipoprotein L1 (APOL1)-risk variants or other genetic disorders. We review the evolution of CGP, and its history and proposed pathomechanisms. We also present the disease spectrum from our experience with emphasis on recognizing the lesion, distinguishing from mimics and linking the histopathological pattern to a specific cause. Our understanding continues to evolve as clinicians and scientists work toward a more complete understanding of the molecular pathways of injury in this disease and how these might be disrupted for therapeutic purposes. Much still remains to be discovered in CGP as the molecular underpinnings leading to disease are still not completely understood and no effective treatment exists despite the high morbidity. Based on this rapid evolution, CGP is a modern template of how we diagnose and think about kidney disease. The story of CGP represents the current shift in nephrology and nephropathology from morphology-alone-based diagnosis to a comprehensive approach including molecular diagnostics. We believe this new, holistic approach will lead to pathogenesis-centered diagnoses that will help to individualize risk stratification and treatment protocols.

In renal allograft recipients, cytomegalovirus (CMV) typically causes tubulointerstitial nephritis. Only rarely glomeruli are involved. We present a rare case of CMV with collapsing glomerulopathy, necrotizing glomerulonephritis, and crescent formation in a renal allograft recipient. Immunohistochemistry confirmed CMV infection. The patient was started on valganciclovir and his renal function remained stable. A repeat renal biopsy performed three months later showed morphologically normal glomeruli and CMV immunostaining was also negative. Nephropathologists have to carefully screen for CMV in cases with crescentic or collapsing glomerulopathy as the later lesions resolve after treating the underlying viral infection. This study will add on to the various glomerular changes associated with CMV infection.

Hemophagocytic syndrome (HPS) is a rare condition caused by dysregulated activation of the immune system leading to infiltration of bone marrow and organs by nonmalignant macrophages that phagocytose blood cells. Primary HPS is caused by inherited immune dysregulation whereas secondary HPS is triggered by neoplastic, infectious or autoimmune diseases. Clinically, the syndrome presents with continuous high-grade fever in association with multi-organ involvement. Few data are available regarding renal manifestations of HPS. We report a 60-year-old patient with NK/T cell nasopharyngeal extranodal lymphoma who presented with acute kidney injury and nephrotic range proteinuria in association with fever and pancytopenia. A kidney biopsy was consistent with collapsing glomerulopathy. A final diagnosis of HPS was made on the basis of clinical, laboratory, and bone marrow biopsy findings in accordance with established diagnostic criteria. Steroid therapy was initiated. However, the patient failed to recover his renal function and remained hemodialysis-dependent. Key diagnostic and therapeutic challenges and strategies used to overcome those challenges are discussed.

Collapsing glomerulopathy (CG) is a rare entity as a glomerular disease. Although it has been considered as a variant of focal segmental glomerulosclerosis, the fact is that the podocyte lesions show different features with respect to the typical focal segmental glomerulosclerosis, an aspect that has been attributed to a type of podocytopathy. In CG, the podocyte lesion is typically characterised by a dysregulated podocyte phenotype, reflected by the loss of expression of mature podocyte markers. CG can be a primary disease or it can be associated with several causal factors that develop a common histopathological entity. The clinical expressiveness of CG is often characterised by the presence of a nephrotic syndrome and a rapid deterioration of the renal function than other variants of the focal segmental glomerulosclerosis. The prognosis of these patients is a rapid progression towards end-stage renal disease with poor response to treatment.

Genetic variants in apolipoprotein L1 (APOL1) confer risk for kidney disease. We sought to better define the phenotype of APOL1-associated nephropathy. The FSGS Clinical Trial involved 138 children and young adults who were randomized to cyclosporin or mycophenolate mofetil plus pulse oral dexamethasone with a primary outcome of proteinuria remission. DNA was available from 94 subjects who were genotyped for APOL1 renal risk variants, with two risk alleles comprising the risk genotype. Two APOL1 risk alleles were present in 27 subjects, of whom four subjects did not self-identify as African American, and 23 of 32 (72%) self-identified African Americans. Individuals with the APOL1 risk genotype tended to present at an older age and had significantly lower baseline eGFR, more segmental glomerulosclerosis and total glomerulosclerosis, and more tubular atrophy/interstitial fibrosis. There were differences in renal histology, particularly more collapsing variants in those with the risk genotype (P=0.02), although this association was confounded by age. APOL1 risk genotype did not affect response to either treatment regimen. Individuals with the risk genotype were more likely to progress to ESRD (P

Collapsing glomerulopathy (CG) usually presents with reduced glomerular filtration rate, heavy proteinuria and has unfavorable prognosis. Numerous associations with CG are found. We encountered a case of CG associated with pulmonary tuberculosis presenting with proteinuria and dialysis-requiring severe renal failure. Our patient made partial recovery of his renal function and became dialysis-independent after antituberculous therapy and oral steroids. Long-term follow-up is needed to assess the progression of the disease.

Hyperacute renal failure is rarely the initial presentation of systemic lupus erythematosus (SLE). Pregnancy can predispose untreated lupus nephritis to acute renal failure. Collapsing glomerulopathy (CG) type of renal failure is not a new clinicopathological entity. There have been documented cases prior to 1979. It is thought that detection bias coupled with the predilection for HIV has caused this form of glomerulopathy to be incorrectly named or diagnosed as 'malignant focal segmental glomerulosclerosis (FSGS)'. This is a case of CG described in lupus nephritis. We present a case of untreated lupus in a female in whom pregnancy triggered the exacerbation of lupus nephritis that presented as collapsing glomerulopathy.

Collapsing glomerulopathy (CG) is a distinct histopathologic pattern of glomerular injury characterized by global/segmental wrinkling of the glomerular basement membrane with podocyte hyperplasia and hypertrophy along with tubulointerstitial changes. There is no specific treatment for CG due to etiological heterogeneity, and newer insights into the pathogenesis may lead to the development of targeted therapy. The most common form of CG is the primary or idiopathic followed by secondary (due to viral infections, autoimmune disease, drugs, etc.) and genetic causes. Thrombotic microangiopathy (TMA) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ failure of variable severity. We here present two young women with preeclampsia who presented with acute kidney injury, anemia, and schistocytes in peripheral smear suggestive of TMA. Renal biopsy showed interesting histopathology of CG in addition to TMA in the first patient and CG alone in the second. Both the patients received supportive therapy while the first patient also received plasmapheresis. One patient had complete recovery, and other had partial recovery of renal function at last follow-up. Combined histopathological lesion of CG with TMA has never been reported in postpartum period so far in literature.

Galloway-Mowat syndrome (GAMOS [MIM 251300 ]) is a rare autosomal recessive disorder that manifests as a combination of nephrotic syndrome, brain abnormalities and developmental delay. It is a clinically and genetically heterogeneous disease. The WDR73 variations are associated with GAMOS1. Here we report two consanguineous families affected by GAMOS1. In the first family, three sisters are affected and in the second family, only one index case is identified. They all show a nephrotic syndrome, a neurological involvement and a collapsing glomerulopathy. The analysis of mutations of WDR73 revealed a new homozygous missense mutation NM_032856.3 c.293T > C; p.(Leu98Pro) in two patients from the first family, and a new homozygous missense mutation NM_032856.3: c.767G > A; p.(Arg256Gln) in the second one. This study extended the clinical and molecular spectrum of GAMOS1 with other cases associated with collapsing glomerulopathy and two novel WDR73 variations that are most likely pathogenic.

Thrombotic microangiopathy (TMA) is a poorly recognized cause of collapsing glomerulopathy. The frequency and significance of collapsing glomerulopathy associated with renal TMA have not been specifically studied in native kidney biopsy specimens. Here we retrospectively documented clinicopathologic features of 53 patients with histologically proven TMA in the native kidney, with special emphasis on changes due to focal segmental glomerulosclerosis (FSGS). Histological TMA was related to hypertensive nephropathy in 21 patients, genetic complement abnormalities in 9, drugs in 7, and to other causes in 16 patients. Almost half (26 patients) presented with arteriolar, 6 with glomerular, and 21 with mixed TMA. Using the Columbia classification system for the 53 patients with histological TMA, 33 had concurrent FSGS lesions with collapsing glomerulopathy the dominant variant in 19 patients (58% of the FSGS cases), not otherwise specified in 9 patients, cellular in 3, and perihilar or tip lesions in 1 patient each. The presence of FSGS was associated with a poor renal prognosis, with no prognostic difference between collapsing glomerulopathy and other FSGS variants. Thus, collapsing glomerulopathy is frequently found in native kidney biopsies with TMA, suggesting that endothelial injury may play an important role in the pathophysiology of FSGS.

Background: Collapsing glomerulopathy is a cause of nephrotic syndrome with massive proteinuria secondary to podocyte proliferation and glomerular collapse. It is characterized by an almost inevitable progression to end stage renal failure, poor response to treatment and high post-transplant recurrence. Its frequency has increased in recent years due to its common association with Human Immunodeficiency Virus (HIV) infection and the growing recognition of new etiologic agents such as drugs and parvovirus B19. Therefore, it is a disease of growing interest for clinicians. The aim of this review is to update the clinical presentation, diagnosis, pathogenesis and therapeutic alternatives of this disease.

We report a case of collapsing glomerulopathy associated with natural killer cell leukemia in a previously healthy 27-year-old African American man. An initial kidney biopsy showed findings concordant with the cellular variant of focal segmental glomerulosclerosis. A repeated biopsy 3 months later showed collapsing glomerulopathy, likely representing a morphologic evolution from a cellular variant into the collapsing glomerulopathy variant of focal segmental glomerulosclerosis. Collapsing glomerulopathy has been described in connection with a number of disparate disorders in which podocyte injury seems to be the common denominator. The close temporal association between clinical presentation and the development of nephropathy provides support for a direct pathogenic link between the underlying lymphoproliferative disorder and the glomerular lesions. We hypothesize that dysregulated cytokine production by the neoplastic cells led to podocyte alterations and eventually to the development of collapsing glomerulopathy.

The term 'focal segmental glomerulosclerosis (FSGS)' has been applied to many different conditions. All classifications of 'FSGS', including those describing 'variants', perpetuate the misconceptions that the entities included have something in common and that the term 'FSGS' has some value. With a rigorous approach to renal biopsies showing segmental lesions, especially with knowledge of clinical circumstances and with detailed analysis of features such as the appearance of lesions and their position within glomeruli, a pathologist can provide information that is clinically more useful than merely the bald diagnosis 'FSGS'. More precise terms should be used. 'Overload changes' can be used to describe the changes seen in reduced renal mass. 'Tip changes' can be seen in many conditions and are not a disease in themselves. 'The glomerular tip lesion as originally defined' means the occurrence of tip changes in otherwise normal glomeruli, in the nephrotic syndrome. 'Early classical segmental sclerosing glomerulopathy' is the combination of tip changes and otherwise abnormal glomeruli, in the nephrotic syndrome. 'Late classical segmental sclerosing glomerulopathy' means segmental lesions at various sites within glomeruli, in the nephrotic syndrome. 'Collapsing glomerulopathy' is distinctive, and its inclusion in classifications emphasises the lack of specificity of 'FSGS'.

Collapsing glomerulopathy has increasingly been recognised in patients with conditions other than HIV. The non-HIV form of collapsing glomerulopathy generally shows little response to standard therapies. We describe a 12-year-old girl with a pre-existing diagnosis of systemic lupus erythematosus presenting with renal failure. A renal biopsy gave the histological diagnosis of collapsing glomerulopathy with evidence of "full-house" immunostaining. We propose collapsing glomerulopathy in her case, as no other cause was found was secondary to systemic lupus erythematosus. The immunophenotype of her podocytes suggested a partial de-differentiation that might have been important in her partial response to immunosuppression.

Collapsing glomerulopathy (CG) is considered to be a distinct clinicopathologic pattern of proliferative podocyte injury. The clinical significance of CG in renal allograft biopsies is yet not clear due to the scant data on the occurrence of CG in renal transplant recipients. We identified nine cases of CG in allograft biopsies over a period of 2 years. Detailed clinical information, including follow-up data, was collected and histopathological analysis performed. All the nine patients were males with a mean age at diagnosis of 32.4±11.2 years. The median posttransplantation duration at diagnosis of CG as 52 (range 12-98) months. All the patients presented with severe proteinuria and graft dysfunction. Histological analysis showed a median number of 8 glomeruli. The collapse of the glomerular tuft with visceral epithelial cell hyperplasia involved median of 2 glomeruli (range 1-4). At the last follow-up (mean duration 6 months), four patients had graft failure (return to dialysis) while four had functioning grafts. One patient was lost to follow-up. This series emphasizes the importance of this rare glomerular pathology as an important cause of graft dysfunction that may lead to allograft failure.

Five pathologic variants of FSGS were recently defined ("Columbia classification"), but the stability of these phenotypes in renal allografts remains unknown. We hypothesized that if the variants represent distinct diseases, then the pattern of recurrent FSGS in renal allografts will mimic the original disease in the native kidney. This multicenter study included 21 cases of recurrent FSGS from 19 patients who had both native and transplant biopsy samples available for analysis. These results support the Columbia classification, because 81% recurred in the same pattern as the original disease, but three variants manifested plasticity from native to allograft kidneys or in the pattern of recurrence (four FSGS, not otherwise specified [NOS] to collapsing variant, two collapsing variant to FSGS NOS, and one cellular variant to FSGS NOS). No transitions between the cellular and the collapsing variants were observed, supporting the view that these are separate entities. Three categories of recurrence were observed: Type I, recurrence of the same variant of FSGS; type II, recurrence of the same FSGS variant, preceded by a minimal change-like lesion; and type III, recurrence of a different FSGS variant in the allograft. Thus, potential evolution of the pathologic phenotype should be considered in pathologic interpretation and clinical trials.

Collapsing glomerulopathy is a proliferative disease defined by segmental or global wrinkling of the glomerular basement membranes associated with podocyte proliferation. These lesions are particularly poor responders to standard therapies. First described as an idiopathic disorder or following HIV infection, it is now associated with a broad group of diseases and different pathogenetic mechanisms, which participate in podocyte injury and mitogenic stimulation. Because of this etiologic heterogeneity, there is clear need for new therapeutic approaches to target each variant of this entity. Historical background, terminology, morphologic and phenotypic features, and suggested mechanisms are reviewed in this manuscript.

Background Renal toxicity has been reported with bisphosphonates such as pamidronate and zolidronate but not with ibandronate, in the treatment of breast cancer patients with bone metastasis. One of the patterns of bisphosphonate-induced nephrotoxicity is focal segmental glomerulosclerosis (FSGS) or its morphological variant, collapsing focal segmental glomerulosclerosis (CFSGS). Case presentation We describe a breast cancer patient who developed heavy proteinuria (protein/creatinine ratio 9.1) and nephrotic syndrome following treatment with oral ibandronate for 29 months. CFSGS was proven by biopsy. There was no improvement 1 month after ibandronate was discontinued. Prednisone and tacrolimus were started and she experienced a decreased in proteinuria. Conclusion In patient who develops ibandronate-associated CFSGS, proteinuria appears to be at least partially reversible with the treatment of prednisone and/or tacrolimus if the syndrome is recognized early and ibandronate is stopped.

Hemophagocytic syndrome (HPS) is defined by bone marrow and organ infiltration by activated, nonmalignant macrophages, which phagocytose blood cells. The clinical spectrum of HPS is broad, but renal involvement has rarely been investigated. We report a previously unknown renal manifestation of HPS: nephrotic syndrome. This multicentric retrospective study included patients fulfilling the following criteria: (i) no history of nephropathy; (ii) HPS diagnosis with histologic evidence of hemophagocytosis; (iii) occurrence of nephrotic syndrome during HPS; and (iv) available renal histology. Using the same criteria, we also searched the literature for additional cases. We identified nine patients retrospectively and found two additional cases in the literature (five males and six females, whose mean age was 34 +/- 27 years). Black African patients predominated (63.6%). HPS was due to lymphoma (six cases), infectious disease (three cases), and autoimmune disease (one case), and was primary in one patient. Acute renal failure was associated with nephrotic syndrome in 10/11 cases. Renal histology showed acute tubular necrosis associated with collapsing glomerulopathy in five patients (all Africans with negative human immunodeficiency virus serology), minimal change glomerulopathy in four, and thrombotic-microangiopathy with abnormal podocytes in two. Death occurred in seven cases. Nephrotic syndrome should be included among the renal complications of HPS with acute renal failure. We postulate that abnormal T-cell activation and/or high pro-inflammatory cytokine levels during HPS might cause podocyte injuries, especially among African patients with a susceptible genetic background.

Glomerular collapse is an essential characteristic of collapsing glomerulopathy (CG), a distinctive proliferative renal parenchymal disease defined by the segmental or global collapse of capillary tufts associated with prominent podocyte hyperplasia and hypertrophy. First described in the mid-1980s as an idiopathic disorder or following human immunodeficiency virus(HIV)-1 infection, it is now associated with a broad range of diseases and different pathogenetic pathways which contribute to the podocyte injury and their aberrant proliferation. Although the association between subtotal infarction and de novo CG in transplanted kidneys has recently been reported, to our knowledge, no such association of this lesion with the acute cortical necrosis (ACN) in the native kidneys has been reported in literature to date. We describe 2 cases of glomerular collapse with typical morphological features of CG occurring in the background of ACN in native kidneys and discuss its possible pathogenesis with reference to the existing literature.

A young woman of African descent presented with fevers, arthralgia, lymphadenopathy and a skin rash. Modest proteinuria was also noted. The clinical picture suggested an acute HIV sero-conversion illness, and a renal biopsy showed a collapsing glomerulopathy compatible with that diagnosis. However, HIV serology proved persistently negative and a diagnosis of Adult Still's disease was subsequently made (by Yamaguchi criteria). Following steroid treatment, the patient's fever abated and her inflammatory markers returned to normal. Collapsing glomerulopathy is a rare but important complication of Adult Still's disease. Immunosuppressive treatment may be effective in improving renal outcome.