Focal segmental glomerulosclerosis as the leading cause of idiopathic nephrotic syndrome: a different spectrum revealed by mandatory renal biopsy in all patients

Introduction: Idiopathic nephrotic syndrome (INS) is associated with varied glomerular lesions. The evidence so far confirms a higher incidence of minimal change disease (MCD) than other subtypes in children. Different newer trials and review literature suggest a 2-fold increase in the incidence of focal segmental glomerulosclerosis (FSGS) in recent decades. Objective: To determine the histopathology of INS following mandatory renal biopsy Method: The patients attending the Department of Paediatric Medicine with a diagnosis of INS were selected for the study. A confirmatory diagnosis was established. Thereafter all patients underwent a mandatory renal biopsy (after exclusion of any absolute contraindication) and histopathology examination. Different findings were compared between MCD and Non-MCD groups (those having histological lesion other than MCD). Results: There were 52 children suffering from nephrotic syndrome (NS) whom we included in our study. The most frequently noted glomerular lesion was FSGS in 45%. MCD was noted in 27%, mesangioproliferative glomerulonephritis (MSGN) in 12%, membranoproliferative glomerulonephritis (MPGN) in 10% and membranous glomerulonephritis (MGN) in 6%. The incidence of relapse was significantly higher in the Non-MCD group (p=0.02). Conclusions: In our study, a mandatory renal biopsy in all patients found FSGS to be the most _________________________________________ College of Medicine and Sagore Dutta Hospital, India, Medical College Kolkata, India *Correspondence: swarnalijoardar@gmail.com (Received on 15 May 2015: Accepted after revision on 19 June 2015) The authors declare that there are no conflicts of interest Personal funding was used for this project. Open Access Article published under the Creative Commons Attribution CC-BY License. common glomerular lesion among paediatric age group patients suffering from INS. (


Introduction
Nephrotic syndrome (NS) in children remains a common cause for hospital admissions in paediatric wards with an annual incidence of 2-7 per 100,000 children, and a prevalence of 12-16 per 100,000 1 .Idiopathic nephrotic syndrome (INS), is associated with glomerular diseases intrinsic to the kidney including minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous glomerulonephritis (MGN), membranoproliferative glomerulonephritis (MPGN), mesangioproliferative glomerulonephritis (MSGN) and others.MCD still remains the most prevalent cause of INS.The frequency of FSGS associated with INS appears to be increasing.A review of the literature suggested a 2-fold increase in the incidence of FSGS 2 .However, other studies have not found such evidence 3 .In almost all of these studies, renal biopsy was only selectively done in patients according to the recommendations for renal biopsy.Other patients who did not meet the criteria for biopsy were mostly considered as presumed MCD.Thus we decided to conduct a study where renal biopsy will be done in all patients excepting only those with contraindications.This may reflect the actual proportion of histological subtypes among INS patients.

Method
The patients attending the Department of Paediatric Medicine in Medical College, Kolkata with a provisional diagnosis of INS were selected for this observational cross-sectional study after proper assessment of inclusion and exclusion criteria: Inclusion criteria: (i) All diagnosed patients of INS.(ii) Age group -more than 6 months to less than 12 years.

Exclusion criteria:
(i) Any chronic disease / comorbidity other than NS.
(ii) Patients with any contraindications for renal biopsy.
A proper and relevant history and clinical examination were performed.Signs and symptoms that may suggest a secondary condition were searched for e.g.malar rash, adenopathy, arthritis, etc. Anthropometric measurements including body weight, height, etc. were taken on admission and weight was recorded daily.After resolution of oedema to the maximum possible extent, the final weight measurement was recorded to assess the nutritional status of the patient.Thus we tried to eliminate the confounding effect of oedema on assessment of nutritional status.Finally they were thoroughly investigated to diagnose INS.Other tests, to exclude secondary nephrotic syndrome, were done as required e.g.ANF, Hepatitis B, Hepatitis C, and HIV serology etc.
Renal biopsy was done in 56 patients having a confirmatory diagnosis of INS, irrespective of whether biopsy was indicated or not, after obtaining proper ethical clearance and after ruling out contraindications to the procedure by doing prothrombin time / INR, urine culture and ultrasonography.Renal biopsy was done under ultrasonic guidance from the back at the renal angle using an appropriate sized BARD biopsy gun.At least 10 glomeruli examined during histopathology was considered adequate.The same experienced pathologist performed histopathology.Four patients were excluded due to inadequacy of the renal biopsy specimen.The final statistical analyses were performed on 52 patients.Standard definitions to define the course of nephrotic syndrome were used 4 .

Statistical analysis:
The observed results were compared between different sub-groups using appropriate standard statistical tests.Unpaired Student's t test was used for normally distributed variables, Chi-square test was used for nominal categorical variables.P value < 0.05 was taken as significant.

Results
There were 52 children suffering from INS whom we finally included in our study analysis.Mean age of the patients was 4.75 ± 2.84 years.Most of the patients were below the age of 8 years (Figure 1).

Figure 1: Age distribution of the patients
On subgroup analysis, mean age of patients with FSGS was 4.48 years and MCD was 3.96 years.There were 30 (57%) males and 22 (43%) females.Similar sex proportions were noted in subgroups with 62.5% males among FSGS.A slightly higher male predominance (71.4%) was noticed among MCD patients.The numbers of MSGN, MGN andr MPGN patients were too small to comment on age or sex prevalence.Among the 52 patients, 11 (21%) showed grade 1 stunting according to Waterlow classification and 13 (25%) had evidence of grade 2 stunting (Figure 2).

Figure 2: Distribution of stunting in subgroups
Considering weight for height as corroborative of acute malnutrition in children up to 5 years according to WHO Z-score Chart, 5 patients (15%) had low weight for height, and 1 patient (3%) had severe acute malnutrition.Calculating body mass index (BMI) in those above 5 years a higher proportion 37% (7 out of 19) of severe malnutrition was found.

Figure 3: Distribution of haematuria patients between different subgroups
Haematuria was present in 50% of MCD, compared to 52.6% in Non-MCD group.The difference was not statistically significant.

Figure 4: Distribution of hypertensive patients between different subgroups
Comparing the prevalence of hypertension between MCD (14.29%) and Non-MCD (34.21%) group, the difference was not significant.
Classifying the patients according to their past history and records of treatment, 11 (21.2%)patients were suffering from 1 st attack of NS, 16 (30.8%)patients from infrequent relapse and 25 (48.1%) from frequent relapse (Figure 5).

Figure 5: Occurrence of first attack, infrequent relapse and frequent relapse
Comparing the occurrence of relapse between MCD (57.1%) and Non-MCD (86.8%) group, the difference was statistically significant (p =0.02).
Most of the patients suffering from chronic malnutrition were having frequent or infrequent relapses.Among 11 cases of 1 st attack, 2 were found to be steroid dependent and 1 patient showed steroid resistance.Oliguria was present in 3 out of 14 (21.4%)patients with MCD and 8 out of 38 (21.1%)Non-MCD patients (Figure 6)

Figure 6: Distribution of patients with oliguria between MCD and non-MCD
The baseline biochemical profile of the patients is shown in Table 1.Normal values were observed for sodium and potassium.Rise in the lipid fragments of blood, was almost universal within our patients, the most marked and constant feature being hypercholesterolaemia.Mean cholesterol level was 489.65±127.12mg/dl.Baseline biochemical reports were compared between MCD and Non-MCD.The differences observed were non-significant (Table 2).According to histological characteristics of the individual renal biopsy specimens, the most frequently noted glomerular lesion was FSGS in 45%.MCD was noted in 27%, MSGN in 12%, MPGN in 10% and MGN in 6% (Figure 7).A study by Kari JA on determining the changing trends of histopathology in childhood nephrotic syndrome in western Saudi Arabia revealed significant statistical findings 6 .In this study the clinical data of 46 paediatric patients diagnosed with INS between 1997 and 2001, were reviewed and compared with data of 132 patients with INS diagnosed between 1983 and 1992.There was a clear decline in the incidence of MCD in recent years from 79.5% to 65% (p=0.02)(even after assuming that all patients without a histological diagnosis had presumptive MCD and the total incidence of MCD = biopsy proven + presumptive).The incidence of FSGS was significantly greater in biopsies performed in the recent period, 35% versus 16.7% in earlier period (p=0.05).Similarly, they found an increased incidence of MPGN in total patients 13.0% and group B, 5.3%, (p=0.02).

Table 2: Mean value ± standard deviation and p-value for different biochemical parameters between minimal change disease and non-minimal change disease group
Another study conducted in Lucknow, India  8 also reported a similar conclusion clarifying the facts that before 1990, FSGS was diagnosed in 23% of all renal biopsies but increased to 47% afterward (P = 0.02).This pattern was observed in all ethnic groups.In African Americans, there was a trend for an increase in the incidence of FSGS from 38% before 1990 to 69% after 1990.A similar trend was observed in Caucasians (from 20 to 45%) and Hispanics (from 8 to 33%).Hispanics had the highest incidence of MCD (biopsy proven + presumptive: 73%), followed by Caucasians (53%) and African Americans (37%).
All studies mentioned so far were mostly based on records of patients who underwent renal biopsy according to standard indications.Hence many patients were excluded from having a confirmatory histological diagnosis and were presumed to have MCD.Even among those who underwent biopsy, there was a clear surge noted in the incidence of FSGS.Our study was different in a major aspect, that all patients underwent biopsy (unless there was some contraindication).Our results were varying markedly in view of the fact that FSGS had a clearly higher incidence compared to MCD.So whether FSGS is exceptionally predominant in our set of paediatric population or whether mandatory renal biopsy in all had led to an altered aetiological pattern, remains a matter for debate.
The mean age of the patients was not significantly different between MCD and non-MCD, being 4.2 vs 5.08 years respectively.Most of our patients were below the age of 8 years (Figure 1).The median age at presentation was similarly 4.5 years in the study by Ahmadzadeh Ali et al. 19 12,13,14 .Children of African American descent appear to be at greater risk for peritonitis 15,16 .
Complete haemogram revealed that 36 patients (69.2%) were anaemic at presentation.Relative iron deficiency with lower serum iron and ferritin levels, lower levels of erythropoietin and decreased physiological response to anaemia may be attributed to this anaemia 17 .Chronic malnutrition may also have played its part.Platelet count was on the higher side in most of the patients with a mean of 5.81 ± .83lacs/cu mm.Thrombocytosis was observed in 55.8% (n=29) patients taking 4.5 lacs/cu mm as the upper cut off.The high risk of thromboembolic complications in patients with a nephrotic syndrome have been ascribed to various abnormalities in plasmatic coagulation including increased production of fibrinogen, Factor V and VIII, reduced fibrinolysis, etc.The following platelet abnormalities were also seen in various studies: increased platelet counts, enhanced platelet adhesiveness, increased spontaneous aggregation and increased heparin neutralizing activitv (PF 4 funct.) 18.Our incidental finding of thrombocytosis further strengthens these aspects of platelet abnormalities.As platelet aggregation and other relevant studies in this regard were not included in our protocol we did not perform any further investigations in this line.
Liver function tests revealed normal bilirubin & liver enzymes.Albumin was decreased in all patients in varying degrees with a mean of 1.8 ± 0.42 g/dl at admission (range: 1.1 to 3 g/dl).Globulin was also decreased substantially with a mean of 2.12 ± 0.4 g/dl.Renal function tests showed more or less normal limits.Blood urea was marginally elevated in 14 patients.These biochemical parameters were compared between MCD and Non-MCD (Table 2).Rise in the lipid fragments of blood, was almost universal within our patients, the most marked and constant feature being hypercholesterolaemia.Among our patients, 2 children (4.9%) had positive Mantoux test considering 10 mm as cut off for immunocompetent children.These two patients were suffering from 1 st attack and had to be treated by anti-tuberculous drugs for 2 weeks before starting steroid therapy.

Conclusions
A mandatory renal biopsy in all patients with INS revealed an enhanced prevalence of FSGS and also suggested that MCD now lags behind FSGS in terms of causation.
Ethical considerations: All human studies have been reviewed by the ethics committee of our Institution and have therefore been performed in accordance with the ethical standards laid down in an appropriate version of the 2000 Declaration of Helsinki as well as the Declaration of Istanbul 2008.Parents/ Guardians of all children gave their informed consent prior to inclusion of their children in the study.

Figure 7 :
Figure 7: Distribution of patients according to histological lesion in renal biopsy Discussion According to the literature, MCD still remains the most prevalent cause of INS.However our study revealed a different proportion from the usual existing trend with FSGS leading the group in a substantial 45% of cases, while MCD lagged far behind.A review article by Borges FF et al. published in Pediatric Nephrology in 2007 2 reviewed the increase in the frequency of FSGS.They compared the frequency of FSGS in two consecutive periods over the past three decades.The results suggested that a shift in the pathological pattern of NS in children might be occurring, resulting in an increase in FSGS frequency.Another large review analysed a 17-year database covering a 275,000-child population with mandatory referral 5 .They confirmed the increasing incidence of FSGS in children with idiopathic NS, but at the same time, found no reason to change the initial therapy and current indications to perform renal biopsy in childhood NS.

Table 1 : Overall baseline mean value ± standard deviation for different biochemical parameters
were anaemic at presentation.Only 9 patients showed evidence of leucocytosis.Platelet count was on the higher side in most of the patients with a mean of 5.81±0.83lacs/cu mm.Thrombocytosis was observed in 55.8%.Liver function tests revealed normal bilirubin, liver enzymes.Albumin was decreased in all patients in varying degrees with a mean of 1.8±0.42g/dl at admission (range: 1.1 to 3 g/dl).Globulin was also decreased substantially with a mean of 2.12±0.4g/dl.Renal function tests showed more or less normal limits.If 40 units is taken as cut off for blood urea, 16 patients had a marginally elevated blood urea.