Familial collapsing glomerulopathy: clinical, pathological and immunogenetic features

Thrombomodulin Gene Mutation and Associated Predisposing Factors in Familial Collapsing Glomerulopathy

Collapsing glomerulopathy (CG) is a rare glomerular disease and its familial form is even rarer. CG and non-collapsing forms of focal segmental glomerulosclerosis may both be caused by pathogenic variants in the same genes, but there is less information on genetics of the former disease. We hypothesized that different hits (viral infection and genetic variants) may be involved in the development of a familial CG here described. We performed renal and etiological routine evaluation, PVB19 serology, genetic tests including whole-exome analysis and dosage of serum thrombomodulin (THBD) in two siblings with CG, one healthy sister, and their mother. The THBD gene variant p.A43T in homozygosity was identified in the proband and her affected brother, both with CG. The same mutation was identified in their mother in heterozygosity. THBD levels were elevated in the serum of both affected siblings. They also had PVB19 positive serology and the G1 high-risk apolipoprotein L1 (APOL1) alleles in homozygosity. Their healthy sister had no PVB19-positive serology and no THBD nor APOL1 gene variants. In this case of familial CG, THBD, and APOL1 gene variants, and a previous PVB19 infection may be associated with the development of CG in a multihit process. In addition, the p.A43T THBD variant, identified in the affected siblings, has never been previously described in homozygosis, pointing to a likely autosomal recessive CG trait caused by this gene mutation.

Collapsing glomerulopathy: update

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.

Collapsing glomerulopathy: a 30-year perspective and single, large center experience

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.

Collapsing glomerulopathy in 19 patients with systemic lupus erythematosus or lupus-like disease

BACKGROUND AND OBJECTIVES

Collapsing glomerulopathy is a podocytopathy with segmental or global wrinkling and collapse of capillary walls and overlying epithelial cell proliferation. Idiopathic collapsing glomerulopathy is a distinct clinicopathologic entity with significant proteinuria, poor response to immunosuppressive therapy, and rapid progression to renal failure. Collapsing glomerulopathy is associated with viral infections, autoimmune disease, and drugs. This work presents the largest group of collapsing glomerulopathy in patients with SLE.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Clinicopathological features were retrospectively studied in 19 patients with SLE (16 patients) or SLE-like (3 patients) disease with collapsing glomerulopathy.

RESULTS

Initially, 95% of patients had nephrotic syndrome with proteinuria of 3-12 g per 24 hours, creatinine levels of 0.6-9.6 mg/dl, positive lupus serologies, and normal complement levels in 63%. Segmental and/or global collapsing glomerulopathy was seen in 11%-77% of glomeruli. Tubular atrophy with focal microcystic changes and interstitial fibrosis was seen in 35% of patients. Minimal glomerular mesangial deposits were noted in 63% of patients, and extensive foot process effacement was seen in 82% of patients. Initial treatment was with pulse/oral steroids. Follow-up from 13 patients revealed that 7 patients progressed to ESRD at the time of biopsy up to 21 months later, 1 patient returned to normal creatinine (1.1 mg/dl) without proteinuria, and 5 patients had creatinine of 1.2-3.6 mg/dl with proteinuria of 0.37-4 g per 24 hours.

CONCLUSIONS

Collapsing glomerulopathy may be seen in SLE patients presenting with massive proteinuria with or without lupus nephritis, which may have prognostic significance.

Familial collapsing focal segmental glomerulosclerosis

The majority of patients with non-HIV-related collapsing focal segmental glomerular sclerosis (FSGS) have idiopathic disease. Only a few genetic forms associated with rare syndromes have been described in families. Here we report two families with multiple members who have collapsing FSGS with no clear associated secondary etiology. Genetic analysis revealed a defect in the TRPC6 gene in one family, but excluded all known common inherited podocyte defects in the other family. The course and response to treatment differed dramatically among members of the same family.

Accelerated development of collapsing glomerulopathy in mice congenic for the HIVAN1 locus

HIV-1 transgenic mice on the FVB/NJ background (TgFVB) are a well validated model of HIV-associated nephropathy (HIVAN). A mapping study between TgFVB and CAST/EiJ (CAST) strains showed this trait to be influenced by a major susceptibility locus on chromosome 3A1-A3 (HIVAN1), with CAST alleles associated with increased risk of disease. We introgressed a 50 Mb interval, encompassing this HIVAN1 locus, from CAST into the TgFVB genome (TgFVB-HIVAN1(CAST) congenic mice). Compared to the TgFVB strain, these congenic mice developed an earlier onset of proteinuria, a rapid progression to kidney failure, and increased mortality. A prospective study of these congenic mice also showed that they had a significantly greater histologic and biochemical evidence of glomerulopathy with one-third of mice developing global glomerulosclerosis by 6 weeks of age. An F2 cross between TgFVB and the congenic mice identified a significant linkage (LOD=3.7) to a 10 cM interval within the HIVAN1 region between D3Mit167 and D3Mit67 resulting in a 60% reduction of the original interval. These data independently confirm that a gene on chromosome 3A1-A3 increases susceptibility to HIVAN, resulting in early onset and rapid progression of kidney disease. These mice represent a new model to study the development and progression of collapsing glomerulopathy.

HIV-associated nephropathy: clinical presentation, pathology, and epidemiology in the era of antiretroviral therapy

The classic kidney disease of human immunodeficiency virus (HIV) infection, HIV-associated nephropathy, is characterized by progressive acute renal failure, often accompanied by proteinuria and ultrasound findings of enlarged, echogenic kidneys. Definitive diagnosis requires kidney biopsy, which shows collapsing focal segmental glomerulosclerosis with associated microcystic tubular dilatation and interstitial inflammation. Podocyte proliferation is a hallmark of HIV-associated nephropathy, although this classic pathology is observed less frequently in antiretroviral-treated patients. The pathogenesis of HIV-associated nephropathy involves direct HIV infection of renal epithelial cells, and the widespread introduction of combination antiretroviral therapy has had a significant impact on the natural history and epidemiology of this unique disease. These observations have established antiretroviral therapy as the cornerstone of treatment for HIV-associated nephropathy in the absence of prospective clinical trials. Adjunctive therapy for HIV-associated nephropathy includes angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers, as well as corticosteroids in selected patients with significant interstitial inflammation or rapid progression.

The spectrum of focal segmental glomerulosclerosis: new insights

PURPOSE OF REVIEW

Focal segmental glomerulosclerosis (FSGS) is a disease with diverse histologic patterns and etiologic associations. Genetic, toxic, infectious and inflammatory mediators have been identified. This review will focus on new evidence supporting the potential mechanistic basis underlying the histologic variants and their clinical relevance.

RECENT FINDINGS

Evidence from animal models and in-vitro studies suggests that injury inherent within or directed to the podocyte is a central pathogenetic factor. Disruption of signaling from any of the podocyte's specialized membrane domains, including slit diaphragm, apical and basal membranes, or originating at the level of the actin cytoskeleton, may promote the characteristic response of foot process effacement. Irreversible podocyte stress leading to podocyte depletion through apoptosis or detachment is a critical mechanism in most forms of FSGS. In the collapsing variant, podocyte dysregulation leads to podocyte dedifferentiation and glomerular epithelial cell proliferation.

SUMMARY

Translation studies in humans and new evidence from animal models have provided mechanistic insights into the diverse phenotypes of FSGS.

Molecular pathology of nephrotic syndrome in childhood: a contemporary approach to diagnosis

Molecular and genetic studies in the last 2 decades have shed new light on the understanding of congenital and infantile nephrotic syndrome (NS). Glomerular pathology may appear as minimal change disease, focal segmental glomerulosclerosis, or diffuse mesangial sclerosis, glomerular diseases now recognized as podocyte injuries and in part caused by altered podocyte genes. Even though genetic mutations are not implicated in all infants with NS, the study of familial disease and congenital NS reveals that proteinuria is in many patients due to specific gene mutations. The most common mutations are in 4 genes, 3 of which are podocyte genes: NPHS1 (Finnish nephropathy), NPHS2 (podocin-induced focal segmental glomerulosclerosis), WT1 (diffuse mesangial sclerosis), and LAMB2 (Pierson syndrome). Furthermore, these studies have improved our understanding of steroid-resistant NS in older children, particularly girls, in whom proteinuria may be due to WT1 mutations. Availability of molecular genetic testing and antibodies to specific gene products are closing the gap between histopathology of pediatric glomerular disease and molecular genetic diagnosis. Recognition of NS variants, which may be reversible (eg, mitochondrial mutations, viral disease), is important. This review discusses the most common entities and the differential diagnosis of pediatric NS from the pathologist's point of view, with an emphasis on congenital (<3 months) and infantile (3 months to 1 year) NS in light of molecular and genetic studies.

Idiopathic collapsing glomerulopathy in children

BACKGROUND

Collapsing glomerulopathy (CG) is a clinically and pathologically distinct variant of focal segmental glomerulosclerosis (FSGS). Pathologically similar lesions have been reported in adults and children with human immuno-deficiency virus (HIV) infection. However, there is a recent interest in the recognition of this variant in the absence of HIV infection.

AIM

To evaluate the clinical presentation and outcome of our pediatric patients with idiopathic CG.

METHODS

A sum of six children with idiopathic CG, aged 1-7 years at presentation, were retrospectively identified. Clinical data and renal biopsy were reviewed for all patients. Serum creatinine and estimated GFRs at presentation and last follow-up were compared using the Wilcoxon signed rank test and the risk factors for occurrence of ESRD analyzed using the Cox proportional hazard models.

RESULTS

Steroid-resistant nephrotic syndrome with or without azotemia was the presenting clinical finding in all the cases. The median serum creatinine values at onset and last follow-up were 1.05 and 1.25 mg/dl, respectively (p = 0.128). Following immunosuppressive therapy one patient achieved complete remission of proteinuria, and four were in partial remission. The remaining one patient did not show any change in proteinuria at 6 months of therapy. Two of the six patients progressed to end-stage renal disease within a median follow-up period of 27 months (range 14-96 months).

CONCLUSIONS

Collapsing glomerulopathy is an aggressive variant of focal segmental glomerulosclerosis. All patients with CG should be screened for the underlying etiology, and patients with idiopathic CG should be offered a trial of immunosuppressive therapy.

Current views on collapsing glomerulopathy

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.

A proposed taxonomy for the podocytopathies: a reassessment of the primary nephrotic diseases

A spectrum of proteinuric glomerular diseases results from podocyte abnormalities. The understanding of these podocytopathies has greatly expanded in recent years, particularly with the discovery of more than a dozen genetic mutations that are associated with loss of podocyte functional integrity. It is apparent that classification of the podocytopathies on the basis of morphology alone is inadequate to capture fully the complexity of these disorders. Herein is proposed a taxonomy for the podocytopathies that classifies along two dimensions: Histopathology, including podocyte phenotype and glomerular morphology (minimal-change nephropathy, focal segmental glomerulosclerosis, diffuse mesangial sclerosis, and collapsing glomerulopathy), and etiology (idiopathic, genetic, and reactive forms). A more complete understanding of the similarities and differences among podocyte diseases will help the renal pathologist and the nephrologist communicate more effectively about the diagnosis; this in turn will help the nephrologist provide more accurate prognostic information and select the optimal therapy for these often problematic diseases. It is proposed that final diagnosis of the podocytopathies should result from close collaboration between renal pathologists and nephrologists and should whenever possible include three elements: Morphologic entity, etiologic form, and specific pathogenic mechanism or association.

Collapsing glomerulopathy

Collapsing glomerulopathy (CG) has become an important cause of ESRD. First delineated from other proteinuric glomerular lesions in the 1980s, CG is now recognized as a common, distinct pattern of proliferative parenchymal injury that portends a rapid loss of renal function and poor responses to empiric therapy. Notwithstanding, the rise in disorders that are associated with CG, the identification of the first susceptibility genes for CG, the remarkable increase in murine modeling of CG, and promising preclinical testing of new therapeutic strategies suggest that the outlook for CG as a poorly understood and therapeutically resistant renal disease is set to change in the future. This focused review highlights recent advances in research into the pathogenesis and treatment of CG.

Can systemic lupus erythematosus be the cause of collapsing glomerulopathy?

Collapsing glomerulopathy is a severe form of glomerular injury, closely associated with HIV infection, characterized by the collapsing feature of glomerular damage with frequent tubulointerstitial involvement and rapid progression to terminal renal failure. The etiopathogenesis in non-HIV infected patients remains obscure. We reported a patient whose diagnosis of collapsing glomerulopathy (CG) and systemic lupus erythematosus (SLE) was done simultaneously and described the diseases characteristics suggesting that SLE could be an etiologic factor for the induction of this glomerulopathy, clinical evolution and treatment.

Collapsing glomerulopathy in adult still's disease

Idiopathic collapsing glomerulopathy is a clinically and pathologically distinct variant of focal segmental glomerulosclerosis characterized clinically by a male and Afro-Caribbean racial predominance, proteinuria (often nephrotic range), and rapid progression to end-stage renal failure. Pathologically, the typical changes are global glomerular collapse leading to obliteration of glomerular capillary lumina, hypertrophy and hyperplasia of podocytes, and severe tubulointerstitial changes. A secondary form with almost identical pathologic features is described in association with human immunodeficiency virus infection. We describe a female patient who presented with multisystemic manifestations, including high spiking fever, arthralgias, lymphadenopathy, striking hyperferritinemia, and impaired renal function with proteinuria. Renal biopsy showed classic collapsing glomerulopathy. A diagnosis of adult Still's disease was made on the basis of Yamaguchi's criteria. The patient was treated with steroids, resulting in remission of the rheumatological condition closely paralleled by remission of proteinuria and renal function, thereby strongly suggesting a causative link between adult Still's disease and collapsing glomerulopathy in this patient. We propose that collapsing glomerulopathy ought to be considered in adult Still's disease with unexplained renal insufficiency or proteinuria.

The importance of family history on the development of renal disease

PURPOSE OF REVIEW

Family history of end-stage renal disease is an important risk factor for the subsequent development of nephropathy. Multiply-affected families with members demonstrating end-stage renal disease often contain individuals with disparate etiologies of renal disease. These observations have led to the search for nephropathy susceptibility genes.

RECENT FINDINGS

Genetic loci associated with susceptibility to diabetic (3q, 18q22.3-23) and non-diabetic nephropathy (chromosome 10) have been identified. A mutation in the uromodulin gene (16p11-13) has recently been linked to medullary cystic kidney disease type 2 and familial juvenile hyperuricemic nephropathy. Familial focal segmental glomerulosclerosis is linked to the 1q25-31, 11q21-22, and 19q13 loci in different families. Several research groups are evaluating family members of individuals with nephropathy in an attempt to uncover previously undiagnosed cases of renal disease.

SUMMARY

Family members of individuals with chronic kidney disease are disproportionately affected with unrecognized and asymptomatic nephropathy. Screening of these high-risk relatives for early nephropathy, and for risk factors for nephropathy, will probably lead to successful treatment for nephropathy and slow the growing worldwide epidemic of end-stage renal disease.

Collapsing glomerulopathy coexisting with membranous glomerulonephritis in native kidney biopsies: a report of 3 HIV-negative patients

Collapsing glomerulopathy (CG), a variant of idiopathic focal segmental glomerulosclerosis (FSGS), can occur in both human immunodeficiency virus (HIV)-positive and HIV-negative patients. Idiopathic membranous glomerulonephritis (MGN) has been reported to coexist with FSGS, but rarely with CG. We report 3 HIV-negative patients (2 men, 1 woman) who developed nephrotic syndrome secondary to MGN complicated by CG, with relatively rapid disease progression despite aggressive therapy.