Endocapillary Proliferation was Associated with Unfavorable Outcomes in Children with Henoch-Schönlein Purpura Nephritis and IgA Nephropathy

Introduction: There are limited data on the outcomes in children with Henoch-Schönlein purpura nephritis (HSPN) and IgA nephropathy (IgAN) in limited-resource countries. This study was aimed to evaluate the outcome of HSPN and IgAN and to evaluate the pathological ndings associated with unfavorable outcomes. Materials and methods: This was a retrospective study conducted in children ( ≤ 18 years) diagnosed with HSPN or IgAN, had estimated glomerular ltration rate (eGFR) ≥ 60 mL/min/1.73 m 2 and underwent renal biopsy between year 2002 - 2018 at Ramathibodi Hospital, Bangkok, Thailand. Clinical outcomes were graded according to the outcome classication by Counahan, as follows: favorable [A, normal; B, minor urinary abnormalities (proteinuria < 1 g/1.73 m 2 /day)]; unfavorable [C, active renal disease (proteinuria > 1 g/1.73 m 2 /day and/or hypertension); D, renal insuciency (eGFR < 60 mL/min/1.73 m 2 or died)]. Pathologies were graded according to Oxford classication. Results: A total of 47 patients (28 HSPN and 19 IgAN) were included with means of age at 9.4 ± 2.8 vs 11.3 ± 4.3 years, respectively. After a median follow-up time of 50 months, proportions of favorable outcomes in the patients with HSPN and IgAN were 82.1% (23/28) and 89.5% (17/19), respectively (p-value = 0.685). In multivariate analysis, only endocapillary proliferation (E) was associated with unfavorable outcomes in both diseases with the odds ratio (95% CI) of 12.46 (1.36 - 114.51, p-value = 0.026). Conclusion: The clinical outcomes of most patients with HSPN and IgAN were favorable and comparable. Endocapillary proliferation (E) was only with poor in both diseases.


Introduction
Immunoglobulin A nephropathy (IgAN) and Henoch-Schönlein purpura nephritis (HSPN) are common glomerular diseases in children. HSPN usually presents with involvement of skin, joints and gastrointestinal tract and approximately 20-47% of patients had renal involvement (e.g. proteinuria, hematuria) 1-3 . However, IgAN usually presents with renal limited symptoms such as recurrent hematuria or proteinuria in which diagnosis needs to be con rmed by renal pathology showing mesangial deposition of IgA in glomeruli. Both diseases share common clinical features and pathologies 2 . The clinical, genetic and immunologic features of these conditions are so closely linked that one could consider HSPN as a systemic form of IgAN [4][5][6] . The pathogenesis of both conditions are proposed to be related with galactose-de ciency of O-linked glycans in the hinge region of IgA1 subtype. These structures are recognized by autoantibodies, resulting in the formation of immune complexes in the circulation and deposition of these immune complexes in various organs 5,[7][8][9] .
In IgAN, the previous studies in pediatric patients indicated that 5-year and 20-year renal survival rates were 94-100% and 70-89%, respectively [10][11][12][13][14] . Several factors have impact on the prognosis in patients with IgAN, such as elevated serum creatinine, heavy proteinuria, and hypertension 15 . However, the outcome of IgAN in children is generally a complete resolution of clinical signs and symptoms 4,13,14 . Children with IgAN who have a normal urinalysis after treatment usually do not progress to end-stage renal disease (ESRD) 4 . In HSPN, mild cases usually show a complete resolution of nephritis. However, some studies reported the recurrence rate between 2.7-30% [16][17][18] . Data from unselected cohorts showed that 5-year renal survival rates were between 82-95% [19][20][21] . The unfavorable prognosis of HSPN usually links to severe clinical symptoms or pathology at the initial presentation. There are several studies regarding the outcomes of treatment and pathological ndings in adults with IgAN and HSPN. However, there are limited data on pathological ndings and outcomes of treatment in children in Thailand. The aims of this study were to evaluate the outcomes of HSPN and IgAN and to evaluate the pathological ndings associated with unfavorable outcomes.

Materials And Methods
We performed a retrospective single-center study by reviewing the medical records and renal biopsy Hypertension was diagnosed if blood pressure (BP) ≥ the 95th percentile for age, gender and height on repeated measurements 22 . Proteinuria was de ned as a positive protein in urine dipstick testing or urine protein-to-creatinine ratio (UPCr) ≥ 0.2 g/g. Hematuria was de ned as positive blood in urine dipstick testing or ≥ 5 red blood cells per high-power on microscopic examination of a centrifuged urine specimen. Estimated glomerular ltration rate (eGFR) was calculated by the bedside CKiD equation as follows 23 : eGFR = 0.413 x height (cm)/ serum creatinine (mg/dl) All renal biopsies were performed prior to the initiation of treatment and reviewed by the two experienced renal histopathologists. Stains used for assessment were H&E, PAS, Jones and Masson's trichrome. All specimens were examined by light microscopy, immuno uorescence staining and electron microscopy.
MEST-C criteria in the updated Oxford classi cation were used to describe pathological data which were standardized for classi cation in IgA nephropathy 24 . The MEST-C criteria comprise of mesangial hypercellularity (with M0 and M1) corresponding to ≤ 50% and > 50% of the glomeruli showing hypercellularity, respectively), endocapillary proliferation (de ned as E0, absence or E1, presence), segmental glomerulosclerosis (de ned as S0, absence or S1, presence), tubular atrophy/interstitial brosis (with T0, T1, and T2 corresponding to ≤ 25%, 26%-50%, and > 50% of cortical area involvement, respectively), cellular/ brocellular crescents (with C0, C1, and C2 corresponding to their absence, presence in ≥ 1 and < 25% of glomeruli, and presence in ≥ 25% of the glomeruli, respectively). This classi cation has been validated for use in HSPN in previous adults and pediatric studies 25,26 . However, patients who had missing data, no glomerulus presented in the renal biopsy specimens or an initial eGFR < 60 mL/min/1.73 m 2 were excluded.
The treatment regimen was decided by the attending nephrologists at the time of consultation. Patients who had proteinuria with or without microscopic hematuria received enalapril with the doses ranging from 0.1-0.6 mg/kg/day. If nephrotic-range proteinuria was detected, corticosteroid therapy (prednisolone or intravenous methylprednisolone) was prescribed with the maximum dose of 2 mg/kg/day or not exceeding 60 mg/day. Immunosuppressive agents were also prescribed in corticosteroid-resistant cases.
Clinical outcomes were graded according to the outcome classi cation by Counahan 27 , as follows: A, normal (normal physical examination with normal urine and renal function); B, minor urinary abnormalities (proteinuria < 1 g/1.73 m 2 /day with or without microscopic); C, active renal disease (proteinuria > 1 g/1.73 m 2 /day and/or hypertension); D, renal insu ciency (eGFR < 60 mL/min/1.73 m 2 or died). However, some patients who had no 24-hour urine collection at the last follow up visit, we used protein-to-creatinine ratio > 1 g/g instead of 1 g/1.73/m 2 /day. Outcome A or B were considered as a favorable outcome and outcome C or D were considered as an unfavorable outcome.
The IBM SPSS program version 24 was used for analysis. Data were presented as percentages, mean and standard deviation or median and interquartile range (IQR), as appropriate. Categorical data and proportions were compared using Chi-square test or Fisher's exact test, as appropriate. Student's t-test or Mann-Whitney U test was used for comparison of continuous data between the two groups, as appropriate. Bivariate logistic regression analysis was used to identify the factors associated with the unfavorable outcome. A p-value of less than 0.05 was considered statistically signi cant.

Baseline characteristics and pathological ndings
A total of 75 patients diagnosed with HSPN and IgAN over a 17-year period were reviewed. Twenty-eight patients were excluded from the study due to no renal pathological data or no glomerular presented in the specimen (14), missing data (3) and eGFR < 60 ml/min/1.73 m 2 (10 from IgAN, 1 from HSPN). Therefore, 28 patients (16 males) with HSPN and 19 (12 males) with IgAN were included in the nal analysis. The demographic, clinical, and pathological data are summarized in Table 1. The median number of glomeruli from the renal biopsies was 14 glomeruli ranging from 5 to 44 glomeruli.

Factors associated with unfavorable outcome
Possible risk factors associated with an unfavorable outcome such as gender, age, hypertension, initial acute kidney injury, diagnosis of HSPN or IgAN and pathological ndings are presented in Table 3. In univariate analysis, the only factor associated with unfavorable outcome was the presence of endocapillary proliferation (E1) in the initial renal biopsy. Initial eGFR and acute kidney injury tended to be associated with unfavorable outcome (p < 0.3). In multivariate analysis, we selected the presence of endocapillary proliferation and AKI in the analysis, E1 remained the only factor associated with outcome C or D with the odds ratios (95%CI) of 9.96 compared to E0 (1.05-94.80, p = 0.046) as shown in Table 4.

Discussion
In this study, the factor associated with an unfavorable outcome (C or D) in HSPN and IgAN was the presence of endocapillary proliferation in the initial renal biopsy with the odds ratios (95%CI) of 12.46 compared to E0 (1.36-114.51, p = 0.026). In this regard, Yang et al. reported that endocapillary proliferation was an independent pathological factor in children with HSPN presenting with nephroticrange proteinuria but it did not correlate with the outcome C or D during a follow-up period of 1-4 years 28 . However, recent publication by Inagaki et al. found that E was signi cantly associated with renal outcome in adult patients with HSPN. It showed that event-free renal survival was signi cantly shorter in patients with endocapillary proliferation than without endocapillary proliferation (p = 0.0072) 29 . In IgAN, Halling et al. found that endocapillary proliferation was a signi cant predictor of poor outcome in children with IgAN and it could predict the composite endpoint of progression to ESRD or reduction of eGFR. In addition, the latter study also found that mesangial hypercellularity, tubular atrophy/interstitial brosis and crescents but not segmental sclerosis, were signi cant predictors for poor outcome 11 . Although a systematic review and meta-analysis of 16 retrospective cohort studies with 3893 IgAN patients and found that endocapillary proliferation was not associated with renal failure [HR 1.4 (95%CI 0.9-2.0), p = 0.1] 30 , there were only four studies that included children under 18 years of age and the population included all stages of chronic kidney disease.
In the present study, the baseline characteristics of both groups were similar except for the clinical presentation of hematuria and nephrotic-range proteinuria. As IgAN is renal limited disease, patients usually present with gross hematuria, which is self-detectable and brings the patients to the hospital. However, microscopic hematuria was found incidentally in some patients (15.8%). Apart from hematuria, a larger proportion of patients with HSPN than IgAN had nephrotic-range proteinuria. As HSPN patients were usually diagnosed by skin manifestation and other systemic organ involvement, a renal biopsy was performed only in those patients with HSPN who presented with a signi cant amount of proteinuria.
Therefore, HSPN patients in this study tended to receive corticosteroids more than IgAN due to having signi cant proteinuria or nephrotic-range proteinuria (p = 0.003). followed 141 HSPN children, and showed outcomes A or B in up to 90.2% with 1-year follow-up. Nephrotic and/or nephritic syndrome were found to be an unfavorable predictor for both short and long-term outcomes (p < 0.05) 33 . In IgAN, Bulut IK et al. studied 29 children included some patients with renal failure during mean follow-up time of 10.4 ± 3.51 years and reported that 84.6% had outcomes A or B 34 . All of these studies showed that the overall prognosis of both diseases in general was comparable and had a good prognosis consistent with our ndings.
This study had some limitations. Firstly, it was a retrospective study with a limited number of cases and a short duration of follow-up. Secondly, some other factors could affect the outcome such as different regimens of treatment, different baseline characteristics and different severities of pathological ndings. Therefore, further studies with more cases, subgroup analysis, and longer follow-up time are warranted. In conclusion, the clinical outcomes of most pediatric patients with HSPN and IgAN were favorable and comparable. The presence of endocapillary proliferation in the initial renal biopsy was the only independent factor associated with poor outcomes in both diseases.

Declaration Section
Ethical permission was obtained from the Ethics Committee in Human Research of the Faculty of Medicine, Ramathibodi Hospital (ID 09-61-59 for IgAN and ID 09-61-29 for HSPN).
Consent for publication: not applicable Con icts of interest: The authors declare no potential con icts of interest with respect to this study. Funding: The authors received no nancial support for this study.