Further studies on the glomerular tip lesion: early and late stages and life table analysis

Tip variant of focal segmental glomerulosclerosis: is it truly a benign variant?

BACKGROUND

Even though frequently described as a benign entity, the outcomes of the tip variant of focal segmental glomerulosclerosis (FSGS) have proven to be unclear.

METHODS

This retrospective study includes a cohort of tip variant cases who presented to us from 2009 to 2012 and the analysis of their presenting clinical, histopathological features and treatment outcomes in comparison to the not otherwise specified (NOS) variants from our center in East India.

RESULTS

Of the 224 biopsies of primary FSGS, 30 cases were the tip variant (13.39%). The mean age of presentation was around 29 years, with 57% being males. A nephrotic presentation was seen in 87% of cases, with 20% showing a presentation at <18 years of age for the first time. Global sclerosis, interstitial fibrosis, tubular atrophy and arteriolar hyalinosis were seen more commonly in the NOS variant. Twenty five patients of tip variant received steroid therapy and eight received alternative immunosuppression. Around 87% of the tip variant cases achieved some form of remission in proteinuria and 13.3% had a doubling of creatinine at a median follow-up of 2 years in comparison to NOS group in which 80% achieved some form of remission and 20% had a doubling of creatinine.

CONCLUSION

Though the histopathological features and treatment responsiveness of the tip variant appear to be better than the NOS variety, the prognostic outcome does not seem to be as favorable as implicated previously with an important percentage of patients showing progressive worsening of renal function within a relatively short time span (2 years) in our cohort.

Causes and pathogenesis of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) describes both a common lesion in progressive kidney disease, and a disease characterized by marked proteinuria and podocyte injury. The initial injuries vary widely. Monogenetic forms of FSGS are largely due to alterations in structural genes of the podocyte, many of which result in early onset of disease. Genetic risk alleles in apolipoprotein L1 are especially prevalent in African Americans, and are linked not only to adult-onset FSGS but also to progression of some other kidney diseases. The recurrence of FSGS in some transplant recipients whose end-stage renal disease was caused by FSGS points to circulating factors in disease pathogenesis, which remain incompletely understood. In addition, infection, drug use, and secondary maladaptive responses after loss of nephrons from any cause may also cause FSGS. Varying phenotypes of the sclerosis are also manifest, with varying prognosis. The so-called tip lesion has the best prognosis, whereas the collapsing type of FSGS has the worst prognosis. New insights into glomerular cell injury response and repair may pave the way for possible therapeutic strategies.

Tip variant of focal segmental glomerulosclerosis: outcome and comparison to 'not otherwise specified' variant

BACKGROUND

The clinical significance of focal segmental glomerulosclerosis (FSGS) tip variant remains unclear. With the aim to determine its clinical and histological features, and natural history, we studied our cases of patients with this glomerular lesion.

METHODS

This is a retrospective analysis. All native renal biopsies from patients diagnosed as FSGS, between 1998 and 2006, were revised for cases with tip variant. Glomerulosclerosis (GS), segmental lesions and interstitial fibrosis (IF) were quantified. We analysed clinical and follow-up data and compared with cases of FSGS not otherwise specified (NOS).

RESULTS

In 248 primary FSGS cases, 37 corresponded to tip variant (14.9%). Median age was 17 years (range 1-65); 13 (35.1%) patients were <15 years old, and 56.8% were males. All patients had nephrotic proteinuria. At diagnosis, there were no significant differences for age, renal function and proteinuria between cases with NOS and tip variant. IF, GS and percentage of glomeruli with segmental lesions were higher in NOS than GTL (P < 0.01). At follow-up (n = 25), 15 patients received steroids alone, and 10 steroids and a cytotoxic agent. At a median follow-up of 48.7 months (24.3-86.7), 7 patients (28.0%) progressed to chronic kidney disease (CKD), 4 (16.0%) developed end-stage renal disease (ESRD) and 9 (36.0%) had complete remission. In NOS patients (n = 93), 48 (51.6%) developed CKD (P = 0.04), 20 (21.5%) developed ESRD (P = 0.54%) and 13 (14.0%) had complete remission (P = 0.02).

CONCLUSIONS

Our work does not demonstrate a clearly favourable prognosis in a group of patients with FSGS tip variant. Although in the tip variant there are less chronic renal tissue damage and CKD, and more frequent complete remission of the nephrotic syndrome, there is an important percentage of patients who develop CKD and ESRD.

Glomerulotubular junction abnormalities are associated with proteinuria in type 1 diabetes

Glomerulotubular junction abnormalities, frequent in proteinuric patients with type 1 diabetes, may contribute to the progressive GFR loss in overt diabetic nephropathy. Glomerulotubular junction abnormalities were examined in patients who have type 1 diabetes with a wide range of albumin excretion rates (AER). Renal biopsies from five normoalbuminuric patients, five microalbuminuric patients, six proteinuric patients, and five control subjects were studied by light and electron microscopy. Light microscopy specimens were serially sectioned to find and classify glomerulotubular junctions. Glomerular structural parameters were estimated using stereologic methods. Glomerulotubular junction abnormalities were found in 2% of glomeruli from control and normoalbuminuric patients and in 4% of glomeruli from microalbuminuric patients. In contrast, 71% of glomeruli from proteinuric patients had glomerulotubular junction abnormalities, including five (8%) atubular glomeruli. Electron microscopy findings were typical of diabetic nephropathy. Piece-wise linear regression models with glomerular, glomerulotubular junction, and interstitial parameters as independent variables provided greater GFR (92%; P < 0.005) and AER (95%; P < 0.01) prediction than multiple regression models (81% for GFR and 72% for AER). Thus, glomerular adhesions and glomerulotubular junction abnormalities help to explain the progressive GFR loss that is associated with onset of proteinuria in type 1 diabetes. Moreover, nonlinear models provide better fit for structural-functional relationships in patients with type 1 diabetes.

Clinical and pathologic characteristics of focal segmental glomerulosclerosis pathologic variants

Histologic variants of idiopathic focal segmental glomerulosclerosis (FSGS) may have prognostic value. A recent working classification system has distinguished five FSGS variants. We evaluated a cohort of adult patients with biopsy-proven FSGS diagnosed between March 1982 and July 2001 to determine if subtypes were associated with renal outcome. Renal biopsies were reviewed by two pathologists. Demographic and clinical data were obtained from charts. Outcomes were partial and complete remission of the nephrotic syndrome, and renal failure. The frequency of FSGS variants was: 3% cellular (N=6), 11% collapsing (N=22), 17% tip lesion (N=34), 26% perihilar (N=52), and 42% not otherwise specified (NOS) (N=83). Collapsing FSGS affected younger and more often black patients. Black race was uncommon in tip variant. Collapsing and tip variants had higher proteinuria and lower serum albumin than perihilar and NOS variants. Better renal function and less severe tubulointerstitial injury were observed in patients with tip variant. These patients were more likely to receive steroids and more often achieved complete remission (50%). After a median follow-up of 1.8 years, 23% of patients were on dialysis and 28% had renal failure. Collapsing FSGS had worse 1-year (74%) and 3-year (33%) renal survival compared to other variants (overall cohort renal survival at 1 and 3 years: 86 and 67%). Different histologic variants of FSGS have substantial differences in clinical features at the time of biopsy diagnosis and substantial differences in renal outcomes.

Evolution of nephrotic-associated focal segmental glomerulosclerosis and relation to the glomerular tip lesio11See Editorial by Haas,P. 1188

BACKGROUND

Several entities or variants within focal segmental glomerulosclerosis (FSGS) have been described, but their changes with time and interrelationships are undetermined.

METHODS

Changes with time were studied in two series of segmental sclerosing lesions in the nephrotic syndrome, one of 22 specimens from ten patients in a trial, the other of 176 specimens from 121 consecutive patients.

RESULTS

The earliest lesions were probably all at the tubular origin, equivalent to the tip variant of FSGS. In some patients, lesions remained at this site, but progression to renal failure was accompanied by morphologic progression, with development of lesions at various sites, equivalent to FSGS, not otherwise specified (NOS). Progression was more likely if there were large lesions, abnormal mesangium, and extensive acute tubular damage. Patients with lesions at the tubular origin at presentation had a shorter duration of symptoms and less chronic renal damage than those with multiple lesions, were more likely to have a complete response of the nephrotic syndrome, and were less likely to progress to renal failure. Recurrent nephrotic syndrome occurred in 12 of 14 allografts at risk, and was usually accompanied by lesions at the tubular origin, then multiple lesions.

CONCLUSION

At least some patients with FSGS (NOS) have evolved from the tip variant. The tip variant has been considered a distinct entity. Another interpretation is that it includes two conditions, one an early form of classic FSGS, and the other closely related to minimal change nephropathy (MCN), equivalent to the glomerular tip lesion as originally defined.

Glomerular tip lesion: a distinct entity within the minimal change disease/focal segmental glomerulosclerosis spectrum

BACKGROUND

The glomerular tip lesion (GTL) is a distinctive but controversial histopathologic lesion occurring in patients with idiopathic nephrotic syndrome. The relationship of GTL to minimal change disease (MCD) and idiopathic focal segmental glomerulosclerosis (FSGS) has been disputed.

METHODS

In order to define the clinical features and natural history of GTL, we retrospectively reviewed the presenting clinical features, biopsy findings and outcome of 47 cases. Presenting clinical features of GTL were compared to those of controls with MCD (N= 61) or idiopathic FSGS (N= 50).

RESULTS

The cohort of GTL consisted of 45 adults and two children (mean age 47.5 years; range 12 to 79 years), including 76.6% Caucasians and 53% males. At presentation, 93.6% of patients had edema, 89.1% had nephrotic syndrome (mean urine protein 8.31 g, mean serum albumin 2.27 g/dL, and mean cholesterol 340.6 mg/dL), and 34.8% had renal insufficiency. Mean time from onset of renal disease to biopsy was 2.4 months. At biopsy, glomerular segmental lesions included GTL alone in 26%, GTL and peripheral lesions in 6%, GTL and indeterminate lesions in 36%, and GTL with peripheral and indeterminate lesions in 32%. No initial biopsy contained perihilar sclerosis and most (81%) segmental lesions were cellular. Follow-up data were available in 29 patients, of whom 21 received steroids alone and eight received sequential therapy with steroids and a cytotoxic agent. At a mean follow-up of 21.5 months, 58.6% of patients achieved complete remission of nephrotic syndrome, 13.8% had partial remission, and 27.6% had persistent nephrotic proteinuria. Only one patient progressed to end-stage renal disease (ESRD). Predictors of nonremission included severity of proteinuria at presentation and % peripheral lesions. When compared to controls with MCD and idiopathic FSGS, GTL more closely resembled MCD with respect to high incidence of nephrotic syndrome (P < 0.001), severity of proteinuria (P < 0.05), short duration from onset to biopsy (P < 0.001), and absence of chronic tubulointerstitial disease (P < 0.0054).

CONCLUSION

Within the MCD/FSGS spectrum, GTL is a distinctive and prognostically favorable clinical-pathologic entity whose presenting features and outcome more closely approximate those of MCD.

Atubular glomeruli and glomerulotubular junction abnormalities in diabetic nephropathy

Atubular glomeruli (AG) have been described in several renal disorders. However, little attention has been paid to AG in diabetic nephropathy (DN). Preliminary studies suggested that tip lesions were frequently present in type 1 diabetic (D) patients with proteinuria. The aim of this study was to determine the frequency of AG and their possible relationship with tip lesions in DN. Renal biopsies from eight proteinuric type 1 D patients with normal to moderately reduced GFR (76 +/- 26 ml/min per 1.73 m(2)) and eight normal subjects were studied by light (LM) and electron microscopy (EM). Glomerular volume, volume of the glomerular corpuscle, which is tuft, and the fractional volumes of proximal, distal, and atrophic tubules per cortex were estimated using appropriate stereologic methods. Glomerulotubular junctions were examined on serial sections and classified into glomeruli attached to: normal tubules (NT); short atrophic tubules (SAT); long atrophic tubules (LAT); atrophic tubules with no observable glomerular opening (ATNO); and atubular glomeruli (AG). EM studies showed typical diabetic changes in biopsies, including increased GBM width (P < 0.00001) and mesangial fractional volume (P < 0.0001) and decreased filtration surface density (P < 0.01) compared with normal subjects. Seventeen percent of glomeruli in the D patients were atubular, and 51% were attached to atrophic tubules. Tip lesions were present in all SAT, 64% of LAT, 82% of ATNO, and only 9% of NT and were never observed in normal subjects. The relative volume of AG was smaller than glomeruli in other categories (P < 0.05). Fractional volume of proximal (P < 0.01) and distal (P <0.01) tubules per cortex were decreased, while fractional volume of cortical interstitium (P <0.00001) and atrophic tubules (P <0.01) were increased in D patients. Fractional volume of atrophic tubules, %AG, and percent of glomeruli with tip lesion explained 94% of the GFR variability in diabetic patients (P <0.05). Thus, AG and glomerulotubular junction abnormalities may be important in the development and progression of DN.

Primum non nocere: Should adults with idiopathic FSGS receive steroids?

Corticosteroids have been widely recommended for the treatment of patients with idiopathic focal segmental glomerulosclerosis (FSGS), despite the lack of evidence-based data to support the use of steroids in this disease. The published studies have a number of limitations. They primarily have been retrospective, have included few patients, and have not been uniform with respect to the steroid treatment protocol. Furthermore, side effects associated with corticosteroid use have not been well documented. The Glomerular Disease Collaborative Network's experience with steroids in idiopathic FSGS has shown a low rate of remission even when steroids were used in the recommended doses and for prolonged periods. Recommendations regarding a specific subset of patients who may benefit from steroid treatment are discussed. The controversies regarding steroids in idiopathic FSGS will only be resolved with data from controlled clinical trials.

Pathology of renal diseases in the tropics

Renal diseases unique to the tropics are those that occur in association with infectious diseases including dengue hemorrhagic fever, typhoid fever, shigellosis, leptospirosis, lepromatous leprosy, malaria, opisthorchiasis, and schistosomiasis. These renal complications can be classified on the basis of their clinical and pathologic characteristics into acute transient reversible glomerulonephritis, chronic progressive irreversible glomerulonephritis, amyloidosis, and acute renal failure (ARF) resulting from acute tubular necrosis, acute tubulointerstitial nephritis, and thrombotic microangiopathy. Certain primary glomerular diseases including immunoglobulin (Ig) M nephropathy and focal segmental and global glomerulosclerosis are prevalent in some tropical countries. Renal complications of venomous snakebites also are common in the tropics. This article discusses and summarizes important works in the literature in respect to the clinical syndromes, pathologic features, and pathogenesis of tropical renal diseases both in humans and experimental animal models.

Glomerular tip lesion in minimal change nephropathy: a study of autopsies before 1950

The clinical significance of the glomerular tip lesion, characterized by podocyte prominence, capsular adhesion, and/or intracapillary foam cells at or adjacent to the urinary pole, remains unclear. It has been postulated that this lesion simply represents a response to heavy proteinuria, and cases of nephrotic syndrome with tip lesions, but no other histological abnormalities, may represent a form of minimal change nephropathy (MCN). However, others have reported that such lesions have a clinical course similar to that of primary focal segmental glomerulosclerosis (FSGS), and the tip lesion often is included among histological variants of FSGS. To determine whether tip lesions may be seen in MCN, we examined histological slides of kidneys from pre-1950 autopsies of patients with a diagnosis of lipoid nephrosis, a term that at that time comprised MCN and FSGS. Before the introduction of antibiotics and corticosteroid therapy, patients with nephrotic syndrome frequently died of sepsis. Eight such cases, with autopsies performed from 1924 to 1943, were identified in which no glomeruli had changes typical of classic FSGS or membranous nephropathy. More than 400 glomeruli were present in each case. Patient ages ranged from 3 to 45 years (six patients <11 years), all had marked edema (duration, 2 weeks to 21 months) and heavy proteinuria, and each died of sepsis and/or pneumonia (pneumococcal in six patients). Glomerular tip lesions were found in five of these eight cases (range, 3 to 26 lesions per case; 0.3% to 4.4% of total glomeruli present), with no predilection for the deep, middle, or superficial cortex. No tip lesions were seen in kidneys from autopsies of age-matched patients without a history of glomerular disease. These findings suggest that the glomerular tip lesion can occur in MCN and most likely represents a response to heavy proteinuria that is not disease specific.

Towards a biological characterization of focal segmental glomerulosclerosis

The primary form of focal segmental glomerulosclerosis (FSGS) has become one of the most common causes of end-stage renal disease in children and adolescents. FSGS was initially considered to be the histological expression of a single disease entity. However, evidence accumulated during the past four decades indicates that FSGS is heterogeneous in nature. It therefore is not surprising that the many therapeutic combinations and permutations that have been tried have yielded variable results in different hands. This has generated substantial confusion and frustration among physicians and patients alike. Recent progress in genetics and molecular biology has opened promising new vistas of investigation. Identification of genes that control components of the glomerular capillary, proteins that form the structural basis of podocytes, and genetic mutations that affect the integrity of these structures has revolutionized our understanding of the glomerular filtration barrier. Substantial progress also has been made in understanding the mechanisms that lead to progression of renal disease and, ultimately, sclerosis. Studies of these factors are likely to yield a mechanistic-based classification of FSGS that will allow us to design therapeutic regimens suited to specific subtypes of this disease.

The role of podocyte injury in the pathogenesis of focal segmental glomerulosclerosis

The podocyte has diverse functions including glomerular filtration, biosynthesis and maintenance of the glomerular capillary architecture. It discharges these functions by virtue of a unique morphology, an intimate relationship with the capillary wall, and diverse synthetic and membrane specializations. Despite the complex role that it plays in glomerular function, the clinical manifestations of podocyte dysfunction are limited to proteinuria and renal insufficiency. Recurrent focal segmental glomerulosclerosis (FSGS) in renal transplants provides a unique opportunity to study the pathogenesis of FSGS in human beings, because the patients are monitored carefully to identify the onset of disease, the recurrence is presumed to have the same etiology as the primary disease, renal biopsy is a tool to study the pathogenesis of the lesion, and therapeutic intervention provides a mechanism to test pathogenesis. Pathologic studies have identified a proliferative lesion of the podocytes as the first sign of recurrent disease. The glomerular lesions evolve to form segmental glomerular scars with time. These findings and studies in experimental models of FSGS implicate podocyte injury in the pathogenesis of the recurrent disease. The cellular lesion (similar to the proliferative lesion of podocytes in recurrent FSGS), seen early in the course of primary FSGS suggests that the pathogenic sequence in recurrent FSGS also applies to primary FSGS. A soluble circulating factor that increases glomerular permeability and correlates with recurrence of FSGS has been identified in the pretransplant serum of patients with end-stage FSGS, but the mechanism of podocyte injury by this factor remains speculative. In any case, podocytes in the cellular lesion undergo morphologic changes and lose specialized functions seen in the normal mature cell, and these structural and functional abnormalities cause the permeability changes associated with proteinuria and destruction of glomerular filtration surface by scarring associated with loss of glomerular function.

The treatment of primary focal segmental glomerulosclerosis

Nephrotic patients with primary focal segmental glomerulosclerosis (FSGS) have a poor prognosis with 50% progressing to end stage renal disease (ESRD) over 3 to 8 years. The achievement of a remission in proteinuria has been associated with a significantly improved renal survival as compared to those patients not attaining a remission. Unfortunately, spontaneous remissions are rare in FSGS, and the response to therapy has historically been poor. Recent experience with more aggressive immunosuppressive therapy has lead to an increase in the remission rate for FSGS patients and given rise to optimism in the treatment of this glomerulopathy.

Glomerular prolapse as precursor of one type of segmental sclerosing lesions

A distinctive segmental glomerular abnormality is confined to the region of the tubular opening. The hypothesis was that this followed prolapse of the tuft into the tubule. Analysis was made of 39 renal biopsy specimens with acute postinfective glomerulonephritis, later material from ten cases, four specimens from three women with pre-eclampsia, and 21 control specimens, with morphometry of glomeruli and immunohistological examination for immunoproteins and monocytes/macrophages. Prolapse was found in 14 specimens with acute postinfective glomerulonephritis, associated in eight with adhesion to Bowman's capsule and local alterations in the tuft, which together constitute early tip changes. Another three had early tip changes only and eight others had thin adhesions between the tuft and capsule next to the tubular opening. Later material confirmed this order of development and showed another late change, with sclerosed and hyaline material in the tuft and adhesion at the tubular origin. Findings in pre-eclampsia were comparable. Glomeruli were significantly larger in acute postinfective glomerulonephritis than in controls and were shown by others to be larger in pre-eclampsia than in normal pregnancy. Immunohistology showed IgM and a few foamy monocytes/macrophages in early tip changes but not in prolapsed loops. Glomerular prolapse appears to be a temporary consequence of acute enlargement of the tuft, probably causes mechanical damage to epithelial cells, and is a precursor of permanent structural changes near the tubular origin. This gives a unifying hypothesis to explain how these changes can be seen in acute postinfective glomerulonephritis, pre-eclampsia, and many other human and experimental renal disorders.

Tuft-to-capsule adhesions and their precursors: differences between the vascular and tubular poles of the human glomerulus

Human glomerular capillary tufts were removed by microdissection and scanning electron microscopy was used to examine the surface of the capillary tuft and the interior of its Bowman's capsule in order to identify connections between the tuft and capsule. Glomeruli were examined in histologically normal renal cortex from 12 kidneys removed for tumour and 12 renal allografts removed for end-stage rejection. In normal kidney, the glomerular tuft was connected to Bowman's capsule by single podocytes and their processes. At the vascular pole, these were predominantly associated with parietal podocytes which lined Bowman's capsule. At the tubular pole, occasional podocytic processes derived from the capillary tuft bridged Bowman's space and connected to Bowman's capsule where there were no parietal podocytes. These podocytic connections were also found in all rejected transplants, but in addition adhesions were identified which consisted of thicker connections between the tuft and capsule. At the vascular pole, tuft-to-capsule adhesions were found in all 12 kidneys; these were always associated with parietal podocytes. Tubular pole adhesions were identified in ten of the 12 transplants. They were associated with abnormal squamous cells, but not with parietal podocytes. When the capillary tuft herniated into the proximal tubule, the tuft sometimes formed an adhesion with the origin of the proximal tubule. These observations suggest that podocyte connections between the glomerular tuft and Bowman's capsule may be precursors of glomerular adhesions at the vascular pole. Since tuft-to-capsule adhesions at the vascular pole differ morphologically from those at the tubular pole, this may reflect different pathogenetic mechanisms at the opposite poles of the glomerulus.

Focal segmental glomerulosclerosis

Over the last 2 decades, we have learnt that focal segmental glomerulosclerosis (FSGS) is a ubiquitous phenomenon underlying the progressive deterioration of many different types of renal diseases in both pediatric and adult populations. FSGS may also be the primary renal lesion, whether in new disease entities such as glycogen storage disease and human immunodeficiency virus infection, or in idiopathic FSGS. Although the mechanism which triggers the development of primary FSGS still remains unknown, laboratory and clinical studies have identified several key pathophysiological events leading to end-stage renal disease. While therapeutic modalities have not changed remarkably, a recent study, although uncontrolled, demonstrated an impressive efficacy of intravenous steroid pulse therapy in inducing remission. Nevertheless, it remains largely unknown whether such a forced remission decreases the overall risk of developing chronic renal failure. Studies have revealed an important pathophysiological role of angiotensin and the therapeutic efficacy of angiotensin converting enzyme inhibitors in progressive loss of renal function in diseases where glomerulosclerosis is secondary; however, it remains to be verified whether these results hold true in primary FSGS. As a result of the improvement in allograft survival rate, the benefit of renal transplant outweighs the risk of recurrence of FSGS, hence transplantation continues to be a vital therapy for FSGS patients who have reached renal failure. Thus, FSGS is not one disease, but rather a range of lesions seen in many settings. The type of lesions and the patient's unique genetic factors contribute to prognosis, and also may dictate choice of optimum therapy.

Pathogenesis of segmental glomerular changes at the tubular origin, as in the glomerular tip lesion

Segmental abnormalities at the glomerulo-tubular junction, or tip changes, are a common and early feature in several experimental and human renal disorders. Scanning and transmission electron microscopic study of an experimental model, Lewis rats given anti-glomerular basement membrane antibodies, showed that at 5 days there were monocytes/macrophages in glomerular capillary loops next to the tubular origin, with abnormalities of visceral epithelium, including prolapse of groups of these cells into the tubular origin. At 12 days, there was contact and adhesion between glomerular capillary loops and Bowman's capsule. Transmission electron microscopic study of human renal biopsies showed that the human tip changes resembled the later lesions seen in rats, with intracapillary foam cells confirmed by immunohistological study to be monocytes/macrophages. These findings show that abnormalities of the glomerular tuft precede adhesion to Bowman's capsule and that the earliest changes recognized by light microscopy in human renal biopsies are relatively late in their natural history, meaning at least several days old. Prolapse of visceral epithelial cells into the tubular origin may explain the characteristic site of tip changes.

Primary focal segmental glomerular sclerosis in adults: prognostic value of histologic variants

Primary focal segmental glomerular sclerosis (FSGS) is a clinicopathologic syndrome in which variable amounts of proteinuria are associated with the renal biopsy finding of segmental glomerular scarring in some, but not all, of the glomeruli. Additional histologic features have been described in FSGS, including the position of the scar relative to the vascular and tubular pole of the glomerulus, foam cells, hyalinosis, mesangial deposits of immunoglobulin M, diffuse mesangial hypercellularity, glomerular visceral epithelial cell hyperplasia and hypertrophy, and the extent of associated interstitial fibrosis and tubular atrophy. We performed a retrospective study on 81 patients with biopsy-proven, primary FSGS to determine whether any of the histologic features of FSGS correlated with renal function at the time of biopsy and the incidence of end-stage renal disease at follow-up. Sixty patients were nephrotic and 21 had nonnephrotic proteinuria. Only the degree of interstitial fibrosis correlated with the initial serum creatinine (r = 0.536) and none of the histologic features predicted the presence of nephrotic-range proteinuria at the time of biopsy. Segmental scars involved 21% +/- 14% of the glomeruli per biopsy specimen, but their position within the glomerulus was uniform in only 13% of the cases. Diffuse mesangial hypercellularity was present in 17% of the biopsy specimens, and glomerular epithelial cell lesions were present in 57% of the biopsy specimens. Multivariate analysis showed that only the degree of interstitial fibrosis predicted end-stage renal disease in all 81 patients and in the 60 patients with nephrotic-range proteinuria. The current data do not support different therapeutic approaches in primary FSGS based on histologic subtypes.

Is focal segmental glomerulosclerosis really focal? Distribution of lesions in adults and children

The distribution of lesions of glomerulosclerosis, whether focal or diffuse, has important implications for pathogenesis and potential therapeutic response. Determination of focal or diffuse nature of lesions from a single section, may, however, be misleading. We therefore evaluated the distribution of segmental glomerulosclerosis in patients with nephrotic syndrome and idiopathic focal segmental glomerulosclerosis (FSGS) by three-dimensional analysis. From our files, we identified all such biopsies with a diagnosis established by immunofluorescence, electron microscopy, and light microscopy that had > 10 glomeruli and serum creatine < 3.5 g/dl. Renal biopsies from 15 adults (9 women, 6 men, age 40.3 +/- 4.2 years and six children (2 girls, 4 boys, age 6.3 +/- 1.4 years) thus identified had sufficient serial sections for analysis. An average of 20.0 +/- 2.6 glomeruli in adults versus 25.2 +/- 3.9 in children were examined. Sclerosis assessed on a single section involved 31.5 +/- 6.8% of glomeruli in adults, contrasting only 11.7 +/- 5.7% in children (P < 0.05). Complete serial section analysis was possible in 14.1 +/- 1.6 and 10.7 +/- 1.6 glomeruli in adults and children, respectively. After this serial section analysis, the percent of glomeruli involved by sclerosis increased to 48.0 +/- 6.6% in adults and 23.2 +/- 7.4% in children (P < 0.025). The pattern remained focal in all but one case that had the highest serum creatinine. The greater increase in sclerosis after serial section analysis in children versus adults reflects the predominance of small peripheral, that is, more segmental, lesions in children than adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary focal segmental glomerulosclerosis: clinical course and response to therapy

Primary focal segmental glomerulosclerosis (FSGS) is a lesion associated with a poor prognosis and results in end-stage renal disease after 5 to 10 years. Based on past experience, many nephrologists have considered primary FSGS a lesion that is steroid resistant and therefore are reluctant to offer steroids as treatment. Recent data, however, have demonstrated that patients with primary FSGS have a response to steroid therapy that is considerably better than had been described. Thus, it may be that nephrologists have been more "steroid reluctant" than the lesion is steroid resistant. To better understand this issue we review the clinical course and response to therapy in patients with primary FSGS.

Segmental sclerosing glomerular lesions

Segmental sclerosing glomerular lesions are usually all grouped together and called focal segmental glomerulosclerosis. This has meant that the term that was originally used for a defined clinical entity is now applied to a variety of conditions in man and experimental animals, with the assumption that the morphological changes are the same in all conditions. Studies of the position of segmental lesions within glomeruli, the size of glomeruli and the proportion of glomeruli affected have shown that this assumption is wrong. Such studies have identified a disease that corresponds to the original clinical concept of focal segmental glomerulosclerosis. This begins with the nephrotic syndrome in patients whose renal biopsies show large glomeruli with mesangial hypercellularity and segmental lesions at every tubular origin. Later the biopsies have segmental lesions throughout the glomerular tuft. This disease differs clinically and pathologically from other conditions that have segmental sclerosing lesions, such as in patients with reduced renal mass or patients with hypertension and proteinuria. The term focal segmental glomerulosclerosis is now too ambiguous and unsatisfactory to be used without qualification.

Focal glomerulosclerosis in idiopathic membranous glomerulonephritis

The significance of the finding of focal glomerulosclerosis (FGS) in idiopathic membranous glomerulonephritis (MGN) is uncertain. Twenty-seven patients with mixed FGS and MGN (MGN-FGS) were compared to 25 patients with MGN alone (generally matched for age, sex and stage of glomerular lesion) with respect to pathology, presenting clinical and laboratory features, and course of disease. Biopsies from the MGN-FGS patients showed significantly more extensive tubulointerstitial disease (P less than 0.001) than did those with MGN alone. At the time of biopsy, the MGN-FGS group had a significantly higher proportion of patients with hypertension (P = 0.006) and microhematuria (P = 0.006), a marginally higher percentage of patients with the nephrotic syndrome (P = 0.051), and a greater mean 24-hour urinary protein excretion (P = 0.004). A similar proportion of patients in each group were treated with either prednisone alone or prednisone with an immunosuppressive. Forty-eight percent of MGN-FGS patients and 13% of the MGN patients developed established renal failure in the follow-up period (P = 0.008). The renal survival rate for the MGN-FGS group was significantly lower at 24 months (0.61 vs. 0.93, P less than 0.05), 60 months (0.48 vs. 0.88, P less than 0.025), and over the entire follow-up period (P less than 0.05). The results indicate that FGS in MGN is associated with a significantly poorer prognosis than MGN without this lesion.

Glomerular tip lesions in renal biopsies with focal segmental IgM

Renal biopsies in which immunohistologic examination had shown the presence of glomerular focal segmental IgM were reviewed in order to investigate the histology and clinical course in these patients. Among 19 such biopsies, 12 had focal segmental glomerulosclerosis (FSGS), whereas seven had only so-called glomerular tip lesions (GTL). GTL also occurred moreover in four of the patients with FSGS. Clinical data suggest a somewhat milder course of disease in the seven patients with GTL as the sole lesion than in the patients of the FSGS group. The nature of GTL is at present unclear. We suggest that GTL may be an initial stage of FSGS, being a lesion that may or may not develop towards FSGS in its typical form. Regardless of its origin, attention is directed to the GTL as a characteristic histologic glomerular lesion, which may be the only significant histologic change in the renal biopsy from a patient with nephrotic syndrome or severe proteinuria.

Determinants of glomerular cross-sectional area

A method of measurement of glomerular cross-sectional area was applied to 267 renal biopsies from 19 groups of patients with well-defined pathological and clinical conditions. There was a correlation between the mean glomerular area for each group and the percentage of global sclerosis in each group. A few groups had glomeruli that were larger than would be expected from their percentage of global sclerosis, probably due to cellular proliferation and/or infiltration. A few groups had glomeruli that were smaller than would be expected from their percentage of global sclerosis, probably due to ischaemic shrinkage. These observations indicate that as well as the known influence of body size on the glomerular area, the number of functioning glomeruli in the body has an important effect on the glomerular area.

Different types of segmental sclerosing glomerular lesions in six experimental models of proteinuria

From 133 to 615 glomeruli were examined in sections of kidneys from each of 60 animals, representing six rodent models of proteinuria. Particular attention was paid to the position of segmental lesions. Lewis rats given sheep anti-rat glomerular basement membrane antibodies had lesions almost exclusively at the glomerulo-tubular junction. Wistar rats on a diet of 24 per cent casein or with subtotal nephrectomy and a diet of 24 per cent soya had lesions mainly at the hilum. Wistar rats given bovine serum albumin had global lesions but virtually no segmental lesions. Wistar rats given puromycin aminonucleoside had lesions at the glomerulo-tubular junction and global mesangial abnormalities shortly after the treatment but later developed segmental lesions at all parts of the glomerulus. Untreated BUF/Mna rats had lesions at the glomerulo-tubular junction early in life but later had lesions at all parts of the glomerulus. Untreated NZB/NZW hybrid mice had various types of glomerulonephritis and also had lesions at the glomerulo-tubular junction. These findings showed that (1) segmental lesions at the glomerulo-tubular junction, or glomerular tip, occur in experimental animals, a fact not previously reported, and these tip changes are a common feature in several different models of proteinuria; (2) hilar segmental lesions are seen in conditions with hyperfiltration of protein; and (3) segmental lesions at various parts of the glomerulus are seen in some models of proteinuria and probably indicate late effects of random toxic damage to the glomerulus. Thus, there are at least three different types of segmental glomerular lesions in experimental animals--tip, hilar, and random--with different morphology and pathogenesis. It is likely that these findings can be extended to human renal diseases with segmental glomerular lesions. This will help to clarify the controversial and unsatisfactory term focal segmental glomerulosclerosis.

The glomerular tip lesion: a distinct entity or not?

Howie and Brewer recently described a novel glomerulopathy: the glomerular tip lesion (GTL). The characteristic feature of this entity is a collection of intracapillary foam cells and marked vacuolization of the epithelial cells of the glomerular segment adjacent to the origin of the proximal tubule. Although this lesion resembles focal segmental glomerulosclerosis (FSGS), Howie and Brewer suggested that it constitutes a distinct entity, differing also clinically from FSGS, in that it would have a better response to steroid treatment. We treated five patients fulfilling the criteria of Howie and Brewer. However, neither corticosteroids (1.5 mg/kg/day for 1 month in five patients) nor cyclosporin-A (5 mg/kg/day for three months in four patients) caused a decrease in proteinuria to below 4 g/day. In two patients, renal function deteriorated and in one of them, recurrence of classical FSGS was found in the renal transplant. A sixth patient was observed in whose biopsy a combination of GTL with membranous glomerulopathy was present. We conclude that GTL is not a distinct entity and that in the clinical course and response to treatment it does not differ from FSGS.

Changes at the glomerular tip: a feature of membranous nephropathy and other disorders associated with proteinuria

Renal biopsies and post-mortem kidneys were examined for segmental lesions at glomerular tips, consisting of adhesion of the tuft to Bowman's capsule with an area of intra-capillary foam cells or hyaline material or sclerosed material. Of 72 consecutive renal biopsies showing membranous nephropathy, 46 (64 per cent) had tip changes. Such changes were correlated with the presence of acute tubular damage and with later stages of the nephropathy, but otherwise seemed unrelated to any particular clinical or pathological feature. Fourteen other patients were identified whose renal biopsies showed tip changes in glomeruli that had segmental or global mesangial hypercellularity not of a well-recognized type such as IgA nephropathy. These patients had persistent proteinuria unresponsive to steroids. Tip changes were also seen in several miscellaneous conditions including IgA nephropathy and diabetic glomerulosclerosis. These findings demonstrate that tip changes are seen in many disorders of the kidney associated with proteinuria and represent a previously unrecognized common response of the glomerulus to some insult, the glomerular tip lesion, as originally defined, is distinguished by the apparent normality of tufts except for the tip changes and can be regarded as presumed minimal change nephropathy plus tip changes and when tip changes are seen, the most important factor determining the prognosis is the condition of the rest of the glomerular tuft.