Biomarkers of IgA vasculitis nephritis in children

Biomarkers to predict kidney outcomes in children with IgA vasculitis

Immunoglobulin A (IgA) vasculitis (IgAV, also known as Henoch-Schoenlein purpura, HSP) is a small vessel vasculitis, most commonly presenting in childhood. In most, it has a straightforward, self-limiting disease course, however some children may develop kidney involvement (IgAV-N) which occurs 4-12 weeks following disease onset and remains the biggest contributor to long-term morbidity. Therefore, children undergo a six-month period of kidney monitoring to identify nephritis via surrogate markers including urinalysis and blood pressure measurements. On-going efforts aim at earlier identification and prevention of nephritis during the window of opportunity between disease onset and established nephritis. By identifying those at highest risk of developing poorer kidney outcomes, the number of children developing chronic kidney disease stage 5 (CKD5) as a result of IgAV-N may be reduced. This review summarizes the latest scientific evidence that support the use of novel biomarkers which may allow nephritis to be identified earlier compared to traditional markers, as well as the risk stratification of children with established IgAV-N. These biomarkers may also enhance the evolving understanding of underlying inflammatory pathways. Promising novel urinary markers of early nephritis include angiotensinogen, Gd-IgA1, various complement proteins, and MCP-1, and serum markers such as α-SMA, C-Met, PTX-3, MMP-9, MRP 8/14, and adiponectin may help identify those at risk of developing CKD5. Prospective, longitudinal, international validation studies are required to investigate these markers further, including exploration of implementation into clinical practice.

Laboratory Findings and Clinical Features in IgA Vasculitis: Identifying Predictors of Kidney Involvement and Disease Relapse in Pediatric Patients

Objective: This study aimed to identify clinical and laboratory predictors of kidney involvement and disease relapse in pediatric patients with IgA vasculitis (Immunoglobulin A vasculitis, IgAV). Materials and Methods: A retrospective cohort study was conducted on 173 children diagnosed with IgAV at the Children's Clinical Hospital of the Medical University of Warsaw between 2018 and 2022. Patients were categorized into groups based on renal involvement (IgAVN+ vs. IgAVN-) and disease recurrence. The analysis included demographic data, clinical manifestations, allergy history, presence of infection, duration of hospitalization, relapse occurrence, the interval between the first and second hospitalization, and laboratory markers. Results: Renal involvement was observed in 42% of cases, while disease recurrence occurred in 9.25% of patients. IgAVN+ patients were older, had longer hospital stays, and more frequently exhibited gastrointestinal symptoms, consistent with previous research. A history of allergic conditions was more prevalent in both the IgAVN+ and recurrence groups. An increase in IgA levels over time was associated with a higher risk of nephropathic development. Patients with recurrences had higher IgM levels and an elevated neutrophil-to-lymphocyte ratio (NLR) (p = 0.07). In the ROC (Receiver Operating Characteristic) analysis, a cutoff value of 1.67 for NLR (AUC 0.71; p = 0.0002; sensitivity 0.87; specificity 0.58) was identified as a risk factor for disease recurrence. Conclusions: Older age at disease onset, gastrointestinal involvement, and allergies are associated with renal involvement in pediatric IgAV. Immune dysregulation, reflected by elevated NLR and IgM, may contribute to disease recurrence. It is important to monitor changes in IgA levels over time, as an increase in IgA concentration is a risk factor for the development of nephropathy. Additionally, calculating the NLR is recommended, as it may indicate the probability of disease recurrence.

Construction and diagnostic efficacy assessment of the urinary exosomal miRNA-mRNA network in children with IgA vasculitis nephritis

This study aimed to comprehensively evaluate the diagnostic potential of urinary exosomal microRNA (miRNA) in IgA vasculitis (IgAV) kidney injury by meticulously comparing the miRNA expression profiles in urine exosomes between children diagnosed with IgAV and those with IgA vasculitis nephritis (IgAVN). Urine samples were obtained from children with IgAV who were treated at our hospital from October 2022 to October 2023. These samples were then categorized into the IgAV group and the IgAVN group. High-throughput sequencing and bioinformatics analysis techniques were employed to conduct a thorough analysis of the differentially expressed miRNAs between the two groups. Additionally, the correlation between urinary exosomal miRNA and clinical parameters was evaluated. A total of 57 urinary exosomal miRNAs exhibited differential expression between the IgAV and IgAVN groups. Specifically, in the IgAVN group, 42 miRNAs were upregulated, while 15 were downregulated. Lasso regression analysis and ROC analysis identified five candidate urinary exosomal miRNAs with high diagnostic accuracy. A prediction of 95 target genes related to the candidate miRNAs led to the construction of an exosomal miRNA-mRNA regulatory network consisting of four key miRNAs and ten hub genes. Gene function and metabolic pathway analyses indicated that these ten hub genes were predominantly enriched in pro-fibrotic and inflammatory pathways. The analysis incorporating clinical parameters demonstrated a significant correlation between hsa-miR-383-5p and urinary protein levels. This research identified exosomal miRNAs and mRNAs with differential expression patterns associated with IgAVN and constructed the corresponding exosomal miRNA-mRNA network. It was determined that hsa-miR-3065-5p, hsa-miR-383-5p, hsa-miR-25-3p, and hsa-miR-450b-5p might mediate the pathogenesis of IgAVN by targeting pro-fibrotic and inflammatory pathways. Among them, exosomal hsa-miR-383-5p is highly likely to serve as a novel non-invasive biomarker for assessing the disease status of IgAVN, thereby offering new perspectives on the non-invasive diagnosis and treatment of IgAVN.

Deciphering the Pharmacological Mechanism of Compound Purpura Decoction in Treating Henoch-Schonlein Purpura by Network Pharmacology, Molecular Docking and Experimental Validation

Henoch-Schonlein purpura (HSP) is an immunoglobulin A (IgA)-mediated systemic vasculitis that frequently develops in children and may progress to serious complications. Compound purpura decoction (CPD), a classical herbal combination, exerts favourable effects on the clinical symptoms and prognosis of HSP; however, the underlying molecular mechanism remains unclear. First, high-performance liquid chromatography analysis identified five bioactive components in CPD, including protocatechuic acid, chlorogenic acid, mangiferin, baicalin and buddleoside, with contents of 0.011 ± 0.02, 0.577 ± 0.33, 0.150 ± 0.05, 1.132 ± 0.23 and 0.369 ± 0.23 mg/g, respectively. Additionally, we established an animal model of allergic purpura to evaluate the therapeutic effects of CPD on HSP. CPD effectively alleviated renal and cutaneous vasculitis and reduced IgA deposition. CPD could regulate the Treg/Th17 cell balance, decrease the levels of the proinflammatory factors interleukin-6 and tumour necrosis factor-α, and suppress the expression of C3 and C5 (p < 0.05). Network pharmacology analysis suggested that the mechanism of CPD in HSP treatment mainly involved epidermal growth factor receptor (EGFR)-related targets and pathways, followed by molecular docking confirming strong binding affinity between EGFR and the bioactive components (binding energy< -4.25 kcal/mol). Real-time quantitative polymerase chain reaction and western blot showed that CPD suppressed the activation of the EGFR/extracellular signal-regulated kinase (ERK) signalling pathway (p < 0.05), which could be associated with the inhibition of complement system activation. This study provides a new perspective for understanding the pathogenesis and treatment of HSP.

Clinical characteristics and risk factors analysis of abdominal symptoms in IgA vasculitis patients: a retrospective cohort study

About 50% of children with IgA vasculitis (IgAV) have abdominal symptoms, usually colic mimic to acute abdomen. Since signs and symptoms of vasculitis may appear in any order, this may affect the diagnosis of children whose abdominal symptoms precede the appearance of purpura. It is necessary to identify the risk factors, pathogenesis, and specific biomarkers to improve the prevention and management of IgAV patients with abdominal symptoms. All the 278 patients were children who had been diagnosed with IgAV in Nanyang Central Hospital between January 2018 and December 2018. The patient's age, gender, clinical manifestations, laboratory examination, and medical history were retrospectively collected. All the patients were divided into two groups based on whether they had abdominal symptoms. Ridge regression and multivariate logistic regression model were used to find risk factors of IgAV patients with abdominal symptoms. Of the 278 patients, 54 patients had abdominal symptoms, and the remaining 224 patients had no abdominal symptoms. Patients with abdominal symptoms had a lower proportion of infections and higher IgM concentrations than patients with other symptoms. For patients over 12 years of age, platelet counts were lower in patients with abdominal symptoms. In addition, basophil count was identified as a protective factor, while IgM was identified as a risk factor. Infections, platelet counts, basophil count, and IgM concentration may be associated with abdominal symptoms in IgAV patients. Basophils and IgM may be involved in the pathological mechanism of abdominal symptoms.

Clinical prediction model for progression from henoch-schönlein purpura to nephritis in pediatric patients

OBJECTIVE

To identify independent risk factors for Henoch-Schönlein purpura nephritis (HSPN) in pediatric patients.

METHODS

This study enrolled 180 pediatric patients (90 with HSP, 90 with HSPN) hospitalized at the 940th Hospital of the Joint Logistics Support Force of the Chinese People's Liberation Army from December 2022 to October 2023, with a follow-up of at least six months. Clinical data were collected at the time of the first onset of HSP. Logistic regression analysis identified risk factors, which were subsequently evaluated using Receiver Operating Characteristic (ROC) curve analysis, a calibration plot, a nomogram, and decision curve analysis.

RESULTS

A predictive model was constructed based on serum cystatin C, serum creatinine, immunoglobulin M, and estimated glomerular filtration rate (eGFR). ROC curve analysis showed high predictive accuracy, with an AUC of 0.9444, sensitivity of 0.82, and specificity of 0.98 at the optimal cutoff point. The calibration curve indicated strong agreement between predicted and actual outcomes. Decision curve analysis suggested that the model provides significant net benefits across different risk thresholds.

CONCLUSION

This model effectively predicts the risk of HSPN, facilitating early intervention and improved patient outcomes.

Blood soluble CD89-IgA complex may be a potential biomarker for predicting multi-organ involvement, especially renal involvement in children with immunoglobulin A vasculitis

BACKGROUND

Immunoglobulin A vasculitis (IgAV) is a kind of systemic vasculitis mediated by IgA immune complexes (IgA-ICs). Soluble CD89-IgA complex (sCD89-IgA) as a type of IgA-IC associated with renal involvement in IgAV, the ability of blood sCD89-IgA as a biomarker to predict renal or multi-organ involvement in children with IgAV is not evident, and this study mainly focused on this.

METHODS

The clinical characteristics and blood samples of 57 pediatric patients with IgAV were collected. ELISA was used to detect plasma IgA-ICs and sCD89-IgA levels. Serum IgA levels were detected by Nephelometry method. Statistical analysis was conducted to analyze the relationship between sex, age, serum IgA levels, plasma IgA-ICs levels, plasma sCD89-IgA levels and the involvement of multiple organs (except skin) including kidneys in these patients.

RESULTS

Compared to patients with simple skin involvement, patients with multi-organ involvement, especially kidneys, had higher levels of plasma IgA-ICs and sCD89-IgA, and the statistical difference was significant. In addition, a high level of plasma sCD89-IgA was a high-risk factor for patients to develop multi-organ or renal involvement in addition to the skin. ROC curve analysis showed that the AUC was 0.861 (Sensitivity: 83 %, Specificity: 88 %, p < 0.0001) when plasma sCD89-IgA predicted multi-organ involvement, and AUC 0.926 (Sensitivity: 94 %, Specificity: 88 %, p < 0.0001) for predicting renal involvement.

CONCLUSIONS

The results suggested that plasma sCD89-IgA may be a potential biomarker for predicting multi-organ involvement (in addition to skin), especially renal involvement in IgAV pediatric patients.

Genome-wide studies define new genetic mechanisms of IgA vasculitis

IgA vasculitis (IgAV) is a pediatric disease with skin and systemic manifestations. Here, we conducted genome, transcriptome, and proteome-wide association studies in 2,170 IgAV cases and 5,928 controls, generated IgAV-specific maps of gene expression and splicing from blood of 255 pediatric cases, and reconstructed myeloid-specific regulatory networks to define disease master regulators modulated by the newly identified disease driver genes. We observed significant association at the HLA-DRB1 (OR=1.55, P=1.1×10-25) and fine-mapped specific amino-acid risk substitutions in DRβ1. We discovered two novel non-HLA loci: FCAR (OR=1.51, P=1.0×10-20) encoding a myeloid IgA receptor FcαR, and INPP5D (OR=1.34, P=2.2×10-9) encoding a known inhibitor of FcαR signaling. The FCAR risk locus co-localized with a cis-eQTL increasing FCAR expression; the risk alleles disrupted a PRDM1 binding motif within a myeloid enhancer of FCAR. Another risk locus was associated with a higher genetically predicted levels of plasma IL6R. The IL6R risk haplotype carried a missense variant contributing to accelerated cleavage of IL6R into a soluble form. Using systems biology approaches, we prioritized IgAV master regulators co-modulated by FCAR, INPP5D and IL6R in myeloid cells. We additionally identified 21 shared loci in a cross-phenotype analysis of IgAV with IgA nephropathy, including novel loci PAID4, WLS, and ANKRD55.

The role of antibody glycosylation in autoimmune and alloimmune kidney diseases

Immunoglobulin glycosylation is a pivotal mechanism that drives the diversification of antibody functions. The composition of the IgG glycome is influenced by environmental factors, genetic traits and inflammatory contexts. Differential IgG glycosylation has been shown to intricately modulate IgG effector functions and has a role in the initiation and progression of various diseases. Analysis of IgG glycosylation is therefore a promising tool for predicting disease severity. Several autoimmune and alloimmune disorders, including critical and potentially life-threatening conditions such as systemic lupus erythematosus, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis and antibody-mediated kidney graft rejection, are driven by immunoglobulin. In certain IgG-driven kidney diseases, including primary membranous nephropathy, IgA nephropathy and lupus nephritis, particular glycome characteristics can enhance in situ complement activation and the recruitment of innate immune cells, resulting in more severe kidney damage. Hypofucosylation, hypogalactosylation and hyposialylation are the most common IgG glycosylation traits identified in these diseases. Modulating IgG glycosylation could therefore be a promising therapeutic strategy for regulating the immune mechanisms that underlie IgG-driven kidney diseases and potentially reduce the burden of immunosuppressive drugs in affected patients.

The efficacy of rituximab in the treatment of IgA vasculitis nephritis

The utility of Rituximab (RTX) for IgA vasculitis nephritis (IgAVN) is not well established. Up to now, we analysed the largest samples of IgAVN patients treated by RTX with a total of 41 retrieved subjects up to December 29, 2023 in the present systematic review. We assessed the clinical profiles, efficacy, and safety of RTX treatments. The present review showed that the renal function tended to be stabilized (P = 1.000) and urinalysis tended to normalize after RTX treatment with no serious adverse events reported. Moreover, 40% (16/40) of patients was freed use of glucocorticoid after RTX administration (P < 0.001). The remission rate was 92.7% (38/41) and complete remission rate was 46.3% (19/41) in IgAVN patients. Interestingly, 76.9% (10/13) of IgAVN child patients achieved complete remission when compared with 32.1% (9/28) of adult patients (P = 0.017). In summary, our results support the benefit of RTX therapy in IgAVN patients, especially children subjects.

IgA Vasculitis and IgA Nephropathy: Two Sides of the Same Coin?

IgA vasculitis (IgAV) is considered a systemic form of IgA nephropathy (IgAN). The two diseases share similar geographic and ethnic distribution, along with common variants in genetic association studies. The pathophysiology of IgAN and IgA vasculitis nephritis (IgAVN) can be explained by the four-hit hypothesis. Key molecules involved at each step in both diseases were evaluated as diagnostic and prognostic biomarkers with many common factors, most prominently serum galactose-deficient IgA1. On kidney biopsy, the two diseases are indistinguishable, and the established histological Oxford classification for IgAN will soon be validated for IgAVN. Chronic lesions (segmental glomerulosclerosis and tubular atrophy / interstitial fibrosis) seem more frequent in IgAN, while proliferative lesions (endocapillary hypercellularity and crescents) are more frequent in IgAVN, which could explain the worse IgAN renal prognosis. Due to characteristic skin rash, IgAVN patients are diagnosed precociously. Conversely, the frequent absence of overt clinical signs in IgAN leads to a delayed diagnostic kidney biopsy in the disease evolution, which explains the chronic pathologic lesions. From a therapeutic perspective, while impressive advances have been made in recent years for IgAN, there is a glaring lack of evidence-based guidelines for the treatment of IgAVN. Large therapeutic clinical studies are required, and future IgAN trials should include IgAVN.

Associations of MEFV gene variants, IL-33, and sST2 with the risk of Henoch-Schönlein purpura in children

Objective

Henoch-Schönlein purpura (HSP) is the most common systemic vasculitis in children. HSP is a multifactorial inflammatory disease, but its pathogenesis is still unclear. The pathogenicity of familial Mediterranean fever gene (MEFV) variants in HSP remains controversial. The objective of this study was to evaluate relationships between MEFV variants and susceptibility to HSP and their associations with clinical outcomes. We also investigated levels of IL-33 and soluble suppression of tumorigenicity 2 (sST2) in children with HSP and their clinical significance.

Methods

We selected 100 children with HSP as the case group. The control group consisted of 50 children who visited the hospital for physical health examinations. All subjects were screened for MEFV gene exon mutations, and levels of IL-33 and sST2 were measured.

Results

The frequency of MEFV variants was significantly greater in HSP patients than in healthy controls. The variant with the highest frequency was E148Q. The frequency of the C allele of the MEFV variant E148Q was 32 % in HSP patients and 18 % in controls (P-adjust = 0.04). Patients with the MEFV E148Q variant had more frequent joint involvement and recurrent purpura and higher levels of IL-33 and C-reactive protein (CRP). Levels of IL-33 and sST2 in children with HSP were significantly higher than those in the control group, and the sST2/IL-33 ratio in children with HSP was unbalanced (P-adjust <0.05). Logistic regression analysis revealed the presence of E148Q and an unbalanced sST2/IL-33 ratio to be independent risk factors for HSP.

Conclusion

The results of this study suggest that the MEFV variant E148Q is associated with HSP susceptibility in Chinese children and that carriers of the variant may have more severe clinical manifestations and greater inflammatory responses. E148Q and the sST2/IL-33 ratio may play important roles in the pathogenesis of HSP.

Insight into the Interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in IgA Vasculitis (IgAV)

The pathogenesis of IgAV, the most common systemic vasculitis in childhood, appears to be complex and requires further elucidation. We aimed to investigate the potential role of galactose-deficient immunoglobulin A1 (Gd-IgA1), high-mobility group box 1 (HMGB1), receptor for advanced glycation end products (RAGE) and protocadherin 1 (PCDH1) in the pathogenesis of IgAV. Our prospective study enrolled 86 patients with IgAV and 70 controls. HMGB1, RAGE, Gd-IgA1 and PCDH1 in serum and urine were determined by the enzyme-linked immunosorbent assay (ELISA) method at the onset of the disease and after a six-month interval in patients and once in the control group. Serum concentrations of HMGB1, RAGE and PCDH1 and urinary concentrations of HMGB1, RAGE, Gd-IgA1 and PCDH1 were significantly higher in patients with IgAV than in the control group (p < 0.001). Concentrations of HMGB1 (5573 pg/mL vs. 3477 pg/mL vs. 1088 pg/mL, p < 0.001) and RAGE (309 pg/mL vs. 302.4 pg/mL vs. 201.3 pg/mL, p = 0.012) in the serum of patients remained significantly elevated when the disease onset was compared with the six-month follow-up interval, and thus could be a potential marker of disease activity. Urinary concentration of HMGB1 measured in the follow-up period was higher in patients with nephritis compared to IgAV without nephritis (270.9 (146.7-542.7) ng/mmol vs. 133.2 (85.9-318.6) ng/mmol, p = 0.049) and significantly positively correlated with the urine albumine to creatinine ratio (τ = 0.184, p < 0.05), the number of erythrocytes in urine samples (τ = 0.193, p < 0.05) and with the outcome of nephritis (τ = 0.287, p < 0.05); therefore, HMGB1 could be a potential tool for monitoring patients with IgAV who develop nephritis. Taken together, our results imply a possible interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in the development of IgAV. The identification of sensitive biomarkers in IgAV may provide disease prevention and future therapeutics.

Erythrocyte Glutathione S-Transferase Activity as a Sensitive Marker of Kidney Function Impairment in Children with IgA Vasculitis

IgA vasculitis (IgAV) is the most common childhood vasculitis. The main cause of morbidity and mortality in children with IgAV is nephritis (IgAVN), but the risk of its development, severity, and chronicity remain unclear. Erythrocyte glutathione S-transferase (e-GST) activity has been previously detected as a sensitive marker of kidney function impairment in several diseases. We spectrophotometrically assessed and correlated e-GST activity between 55 IgAV patients without nephritis (IgAVwN), 42 IgAVN patients, and 52 healthy controls. At disease onset, e-GST activity was significantly higher in IgAVN patients (median (interquartile range)) (5.7 U/gHb (4.4-7.5)) than in IgAVwN patients (3.1 U/gHb (2.2-4.2); p < 0.001), and controls (3.1 U/gHb (1.9-4.2); p < 0.001). Therewithal, there were no differences between the IgAVwN patients and controls (p = 0.837). e-GST activity was also significantly higher in the IgAVN patients than in the IgAVwN patients after 3 months (5.0 U/gHb (4.2-6.2) vs. 3.3 U/gHb (2.3-4.1); p < 0.001) and 6 months (4.2 U/gHb (3.2-5.8) vs. 3.3 U/gHb (2.1-4.1); p < 0.001) since the disease onset. Consistent correlations between e-GST activity and serum creatinine, estimated glomerular filtration rate (eGFR), and proteinuria levels were not detected. In conclusion, increased e-GST activity can serve as a subtle indicator of kidney function impairment in children with IgAV.

A Review of IgA Vasculitis (Henoch-Schönlein Purpura) Past, Present, and Future

The clinical association of purpura, arthralgia, and arthritis was first described in 1837 in a publication by Johann Lukas Schönlein, a German physician. In 1874, Eduard Henoch, a student of Schönlein, reported cases of children with purpura, abdominal pain, bloody diarrhea, and joint pain. IgA vasculitis, or Henoch-Schönlein purpura, is a systemic hypersensitivity vasculitis caused by the deposition of immune complexes in small blood vessels, including the renal glomeruli and mesangium. In the skin, the presentation is with non-thrombocytopenic purpura or urticaria. Worldwide, IgA nephropathy is the most common cause of primary glomerulonephritis. Detection of IgA deposition in small blood vessels and the renal glomeruli is diagnostic in most cases. This article aims to review the history, current classification, epidemiology, presentation, and diagnosis of IgA vasculitis and nephropathy, disease associations or trigger factors, including infections, vaccines, and therapeutic agents, and highlights some future approaches to improve diagnosis and clinical management.

Analysis of IL-1β, TGF-β, IL-5, ACE, PTPN22 gene polymorphisms, and gene expression levels in Turkish children with IgA vasculitis

OBJECTIVE

Immunoglobulin-A vasculitis (IgAV) is an inflammatory disease that affects small blood vessels. This study was performed to identify an association between protein tyrosine phosphatase non-receptor type 22 (PTPN22) + 788G > A (rs33996649), transforming growth factor-beta (TGF-β) -509C > T (rs18004069), interleukin 1-beta (IL-1β) -511C > T (rs16944), interleukin 5 (IL-5) -746C/T (rs2069812), and angiotensin-converting enzyme (ACE) I/D (rs4646994) gene polymorphisms, susceptibility to IgAV, as well as the mRNA levels of IL-1β, IL-1β, and TGF-β.

METHOD

A total of 53 patients with IgAV and 50 healthy controls were enrolled. PTPN22, TGF-β, IL-1β, ACE gene polymorphisms, ACE gene I/D polymorphisms, and mRNA expression levels were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, allele-specific PCR, and real-time PCR with TaqMan kits, respectively.

RESULTS

PTPN22, TGF-β, IL-1β, IL-5, and ACE variants showed no genotype or allele differences between patients with IgAV and controls. Increased levels of IL-1β and TGF-β mRNA expressions were observed in patients with IgAV (p < 0.001). Patients with the IL-1β AG genotype showed significantly increased amounts of arthritis than patients with non-AG (p = 0.004). Age at disease onset was found to be significantly different in patients with IgAV according to the presence of TGF-β TT genotype (p = 0.047).

CONCLUSION

Polymorphisms in PTPN22, TGF-β, IL-5, IL-1β, and ACE genes are unlikely to confer susceptibility to IgAV. However, the presence of the AG genotype of IL-1β is associated with susceptibility to IgAV-related arthritis. This is the first study to report a significant increase in serum mRNA levels of IL-1β and TGF-β in IgAV patients, supporting a susceptibility to IgAV in childhood.

Immunoglobulin A vasculitis nephritis: Current understanding of pathogenesis and treatment

The clinical spectrum of immunoglobulin A vasculitis nephritis (IgAVN) ranges from the relatively common transitory microscopic hematuria and/or low-grade proteinuria to nephritic or nephrotic syndrome, rapidly progressive glomerulonephritis, or even renal failure. Clinical and experimental studies have shown a multifactor pathogenesis: Infection triggers, impaired glycosylation of IgA1, complement activation, Toll-like-receptor activation and B cell proliferation. This knowledge can identify IgAVN patients at a greater risk for adverse outcome and increase the evidence for treatment recommendations.

Present and Future of IgA Nephropathy and Membranous Nephropathy Immune Monitoring: Insights from Molecular Studies

IgA Nephropathy (IgAN) and Membranous Nephropathy (MN) are primary immune-mediated glomerular diseases with highly variable prognosis. Current guidelines recommend that greater immunologic activity and worse prognosis should guide towards the best treatment in an individualized approach. Nevertheless, proteinuria and glomerular filtration rate, the current gold standards for prognosis assessment and treatment guidance in primary glomerular diseases, may be altered with chronic damage and nephron scarring, conditions that are not related to immune activity. In recent years, thanks to the development of new molecular technologies, among them genome-wide genotyping, RNA sequencing techniques, and mass spectrometry, we have witnessed an outstanding improvement in understanding the pathogenesis of IgAN and MN. In addition, recent genome-wide association studies have suggested potential targets for immunomodulating agents, stressing the need for the identification of specific biomarkers of immune activity. In this work, we aim to review current evidence and recent progress, including the more recent use of omics techniques, in the identification of potential biomarkers for immune monitoring in IgAN and MN.

ASSOCIATION BETWEEN HIGH MOBILITY GROUP BOX 1 PROTEIN GENE (rs41369348) POLYMORPHISM AND IMMUNOGLOBULIN A VASCULITIS IN CHILDREN

Immunoglobulin A vasculitis (IgAV) or Henoch-Schönlein purpura is the most prevalent systemic small vessel vasculitis in childhood. High mobility group box 1 protein (HMBG1) is a pleiotropic cytokine that functions as a pro-inflammatory signal, important for the activation of antigen-presenting cells and propagation of inflammation. HMGB1 is implicated in the pathophysiology of a variety of inflammatory diseases. The aim of this study was to investigate the role of single nucleotide polymorphism rs41369348 for HMGB1 gene in the susceptibility and clinical features of patients meeting the classification criteria for IgAV. DNA was extracted from blood cells of 76 children with IgAV and 150 age-matched healthy controls. Clinical data and laboratory parameters were collected for all IgAV patients. Although there was a higher frequency of heterozygous A/delA genotype of this gene polymorphism in IgAV group as compared with control group, no genotype difference was observed between these two groups. No statistically significant genotype differences were disclosed when patients with different IgAV clinical features were compared. In conclusion, in this study, polymorphism rs41369348 for HMGB1 was not associated with increased susceptibility to childhood IgAV, its severity or different clinical manifestations.

Diagnostic and Management Strategies of IgA Vasculitis Nephritis/Henoch-Schönlein Purpura Nephritis in Pediatric Patients: Current Perspectives

IgA vasculitis (IgAV) or Henoch-Schönlein purpura (HSP) is the most common vasculitis in children, and nephritis (IgAVN or HSPN) is the most important and only chronic manifestation of the disease. Despite this, there are no diagnostic criteria and we rely on the European League Against Rheumatism/Paediatric Rheumatology International Trials Organization/Paediatric Rheumatology European Society-endorsed Ankara 2008 classification criteria in our daily practice. Basic investigations that should be done in every patient with IgAVN include blood pressure measurement, estimated glomerular filtration rate and urinalysis. Kidney biopsy is still the gold standard for the diagnosis of IgAVN since noninvasive confirmation of nephritis is still pending. According to the Single Hub and Access point for pediatric Rheumatology in Europe (SHARE) recommendations, the first-line treatment for with mild forms of IgAVN is oral glucocorticoids, for patients with moderate IgAVN parenterally administrated glucocorticoids in pulsed doses, while initial treatment for patients with the most severe forms of IgAVN include pulsed doses of glucocorticoids in combination with intravenous cyclophosphamide pulses. New therapeutic options are currently being tested, aiming to reduce the production of galactose-deficient IgA₁ and autoantibodies or suppress the alternative or lectin complement pathway and blocking mesangial cell activation.

Pathophysiology and clinical manifestations of immune complex vasculitides

Immune complex (IC) vasculitides present inflammations of vessel walls associated with perivascular deposition of immunoglobulins (Igs), mostly ICs. They encompass systemic and skin-limited variants of IgA vasculitis (IgAV), cryoglobulinemic vasculitis (CV), rheumatoid, lupus, and hypocomplementemic vasculitides, serum sickness cutaneous IgM/IgG (non-IgA) vasculitis, and recurrent macular (hypergammaglobulinemic or exertion-induced) vasculitis. Serum sickness and CV fulfill the criteria of a type III hypersensitivity immune reaction as large lattices of the IC precipitate at vessel walls and activate polymorphonuclear neutrophils (PMNs). Immunoglobulin-A vasculitis differs with regard to the causes of perivascular deposition of ICs since here many IgA1 molecules are hypoglycosylated (Gd-IgA1), which appears to facilitate their perivascular deposition in skin and mesangium (via e.g. CD71). The reasons for increased generation of immunoglobulins or formation of IC and their perivascular deposition in either skin or systemic organs are different and not fully explored. A common denominator of OC vasculitides is the activation of PMNs near the vessel wall via Fcy or Fcα receptors. Acute episodes of IgAV additionally require PMNs to become preactivated by IgA1 or by IC already in circulation. This intravascular priming results in increased adherence and subsequently vessel-destructive NETosis when they encounter IgA deposited at the vessel walls. Binding of IgA1 to PMNs in blood stream is associated with increased serum levels of hypogalactosidated IgA1. The characteristic clinical picture of IgAV (and also of so-called IgG/IgM vasculitis) comprises palpable or retiform purpura with a clear predilection for lower legs, probably due to stasis-related reduction in blood velocity, while in other IC vasculitides, additional factors influence the sites of vasculitides. Our knowledge of distinct forms and different pathophysiological pathways of IC vasculitides may lead to in efficacious or targeted therapies. Antibodies to complement components or intestinal budesonide for IgAV are promising agents (the latter suppresses the pathophysiologically related IgA nephropathy by reducing the generation of mucosal IgA.

Hemoperfusion and intravenous immunoglobulins for refractory gastrointestinal involvement in pediatric Henoch-Schönlein purpura: a single-center retrospective cohort study

BACKGROUND

Henoch-Schönlein purpura (HSP) with refractory gastrointestinal (GI) symptoms is always difficult to handle because of its resistance to supportive therapies and glucocorticoid. This study aimed to evaluate the efficacy of hemoperfusion (HP) and intravenous immunoglobulins (IVIG) therapies in this population.

METHODS

Sixty-four HSP patients with refractory GI involvement (R-GI group) and 64 cases with mild GI symptoms (control group) were retrospectively analyzed in our center from March 2016 to October 2019. In R-GI group, 42 cases (subgroup A) were treated with IVIG and steroid, 13 cases (subgroup B) used HP and steroid, 9 cases (subgroup C) executed a combination of IVIG, HP and steroid. Demographic characteristics, clinical features, laboratory indexes and treatment outcomes were recorded. t-test, One-way ANOVA, Mann-Whitney U test, and multivariate logistic regression were used in comparing differences among subgroups and predicting independent risk factors.

RESULTS

Compared with the control group, R-GI cases experienced higher risk of renal involvement (P = 0.000), more steroid exposure (P = 0.000), six times expenses (P = 0.000) and 2.3 times length of hospitalization (P = 0.000). The independent risk factors of R-GI group were elevated neutrophils (OR 1.250 [95% CI 1.130-1.383]) and the percentage of B lymphocytes (OR 1.100 [95% CI 1.026-1.179]) as well as decreased IgG (OR 0.847 [95% CI 0.732-0.98]). In R-GI group, increased age (OR 1.039 [95% CI 1.016-1.062]) and IgM (OR 5.994 [95% CI 1.403-27.611]) were verified to be risk factors of HSP nephritis. All three subgroups could alleviate the symptoms effectively. Compared with those in subgroup A, patients in subgroup B were elder (P = 0.004), had less relapse (P = 0.002), steroid exposure (P = 0.033) and expenses (P = 0.031), more significant decrease of WBC (P = 0.026) after treatment.

CONCLUSION

The HSP with refractory GI involvement had much higher risk of medical burden and renal involvement. Both IVIG and HP therapies could ameliorate refractory GI symptoms efficiently. HP therapy tended to reduce the relapse, costs and steroid exposure in its audiences who were cooperated and with stable hemodynamics, while IVIG had better use in younger children.

Epidemiology and Clinical Characteristics of Henoch-Schönlein Purpura Associated with Streptococcal Infection in 217 Children in Hubei Province, China

Objectives The objectives of present study were to analyze the association of the streptococcal infection with childhood Henoch-Schönlein purpura (HSP) in China. Methods: We performed a case-control study over a period of five years to evaluate the epidemiology and clinical characteristics of group A β-hemolytic streptococcal (GABHS) triggered HSP. Results: 1. The frequency of GABHS-triggered HSP was 15.1%, while that of GABHS infection developing HSP in children was 4.7%. 2.The epidemiological characteristics of HSP with streptococcal infection were similar to those of HSP alone. 3. The GABHS-triggered HSP cases had a significantly higher frequency of renal involvement than the noninfectious group. 4. IgA and IgG were significantly increased in the streptococcal infection group than in the noninfectious group, while the levels of C3 and C4 decreased significantly. Conclusions: GABHS infection is the most frequent agent in HSP children, and may aggravate the immune dysfunction and prolong the course of HSP.

Increased Urinary IgA in Paediatric IgA Vasculitis Nephritis

IgA vasculitis (IgAV) is the most common form of paediatric vasculitis, with up to 50% of patients experiencing kidney inflammation. Much remains unknown about IgAV, but it is believed to arise due to galactose-deficient IgA1 promoting an auto-inflammatory response. This study assesses whether urinary IgA can be detected in children with IgAV to allow further evaluation of IgA1 and whether it has any relationship with nephritis. Urinary and serum IgA concentrations were measured using commercially available ELISA kits. Patients were grouped into IgAV nephritis (IgAVN) or IgAV without nephritis (IgAVwoN). Fifty-nine children were included: IgAVN n = 12, IgAVwoN n = 35, and healthy controls (HC) n = 12, with a mean age of 8.2 ± 4.1 years. Urinary IgA concentrations were statistically significantly higher in patients with IgAV (107.1 ± 136.3 μg/mmol) compared to HC (50.6 ± 26.3 μg/mmol; p = 0.027) and IgAVN (229.8 ± 226.3 μg/mmol) compared to both IgAVwoN (65.0 ± 37.8 μg/mmol; p = 0.002) and HC (p < 0.001). Urinary IgA concentrations were able to distinguish between renal status (AUC 0.838, 95%CI [0.704−0.973], p < 0.001) and did not correlate with proteinuria (r = 0.124; p = 0.407). Urinary IgA concentrations are increased in children with IgAVN, and it has the potential to act as a non-invasive biofluid to further evaluate nephritis in this disease.

IgA vasculitis update: Epidemiology, pathogenesis, and biomarkers

Immunoglobulin A vasculitis (IgAV), formerly known as Henoch-Schönlein purpura, is the most common systemic vasculitis in children, characterized by diverse clinical manifestations with a wide spectrum ranging from isolated cutaneous vasculitis to systemic involvement. The incidence of IgAV is geographically and ethnically variable, with a prevalence in autumn and winter, suggesting a driving role that genetic and environmental factors play in the disease. Although IgAV has a certain degree of natural remission, it varies widely among individuals. Some patients can suffer from severe renal involvement and even progress to end-stage renal disease. Its pathogenesis is complex and has not been fully elucidated. The formation of galactose-deficient IgA1 (Gd-IgA1) and related immune complexes plays a vital role in promoting the occurrence and development of IgAV nephritis. In addition, neutrophil activation is stimulated through the binding of IgA to the Fc alpha receptor I expressed on its surface, resulting in systemic vascular inflammation and tissue damage. Starting from the epidemiological characteristics, this article will review the role of immunological factors such as Gd-IgA1, autoantibodies, circulating immune complexes, complement system, cellular immunization, and the contributions of environmental and genetic factors in the pathogenesis of IgAV, and conclude with the major biomarkers for IgAV.

Advances in IgA glycosylation and its correlation with diseases

Immunoglobulin A (IgA) is the most abundant immunoglobulin synthesized in the human body. It has the highest concentration in the mucosa and is second only to IgG in serum. IgA plays an important role in mucosal immunity, and is the predominant antibody used to protect the mucosal surface from pathogens invasion and to maintain the homeostasis of intestinal flora. Moreover, The binding IgA to the FcαRI (Fc alpha Receptor I) in soluble or aggregated form can mediate anti- or pro- inflammatory responses, respectively. IgA is also known as one of the most heavily glycosylated antibodies among human immunoglobulins. The glycosylation of IgA has been shown to have a significant effect on its immune function. Variation in the glycoform of IgA is often the main characteration of autoimmune diseases such as IgA nephropathy (IgAN), IgA vasculitis (IgAV), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). However, compared with the confirmed glycosylation function of IgG, the pathogenic mechanism of IgA glycosylation involved in related diseases is still unclear. This paper mainly summarizes the recent reports on IgA's glycan structure, its function, its relationship with the occurrence and development of diseases, and the potential application of glycoengineered IgA in clinical antibody therapeutics, in order to provide a potential reference for future research in this field.

Navigating the initial diagnosis and management of adult IgA vasculitis: A review

Background

IgA vasculitis in adults has not been thoroughly studied. This has left a practice gap related to the management and follow-up of a population that is at an increased risk of comorbidities and potentially poor outcomes. For this reason, it is important to synthesize evidence from the current literature because this can help direct the movement for more robust studies to clarify best practice recommendations.

Objective

We sought to create a narrative review for the practicing dermatologist when diagnosing and leading the care of IgA vasculitis in adult patients.

Methods

A broad literature search was performed with a focus on articles that were published after the introduction of the most updated European Alliance of Associations for Rheumatology/Pediatric Rheumatology International Trials Organization/Pediatric Rheumatology European Society criteria.

Results

The characteristics and management guidelines for IgA vasculitis in adults have been refined, although more rigorous studies are needed to develop best practice recommendations.

Limitations

Because of the lack of sufficient randomized controlled trials on IgA vasculitis in adults, this narrative review is composed of mostly observational, descriptive studies.

Conclusion

Adults with IgA vasculitis are at an increased risk of complicated disease course, necessitating formal diagnostic assessment and clear-cut follow-up recommendations to manage and prevent poor health outcomes related to various comorbidities.

Specific immune biomarker monitoring in two children with severe IgA nephropathy and successful therapy with immunoadsorption in a rapidly progressive case

BACKGROUND

Childhood IgA nephropathy (cIgAN) is one of the most common primary glomerulonephritides with the potential to evolve to kidney failure. IgAN is an autoimmune disease involving 3 key factors: galactose-deficient IgA1 (Gd-IgA1), anti-IgA1 autoantibodies, and soluble (s)CD89 IgA Fc receptor. These molecules and immune complexes have been described recently as potential biomarkers of disease progression in childhood IgAN but their evolution in time under immunosuppressive treatment remains unknown.

METHODS

We performed a prospective study of two proliferative cIgAN patients by sequentially biomonitoring immune IgA complexes (sCD89-IgA, IgG-IgA), sCD89, and Gd-IgA1 and correlating them with clinical and histological outcome after treatment.

RESULTS

After patient 1's treatment, a decrease in sCD89-IgA, IgG-IgA, and free sCD89 was linked to a decrease in proteinuria whereas eGFR (estimated glomerular filtration rate) and Gd-IgA1 levels remained stable. Patient 1 received tacrolimus and monthly intramuscular steroid injections of Kenacort for 10 months. At the end, a relapse induced an increase in proteinuria consistent with an increase of the 3 biomarkers. Patient 2 displayed rapidly progressive IgAN with crescents in more than 90% of glomeruli and received intense immunosuppression treatment associated with the immunoadsorption (IA) approach. During IA, proteinuria decreased rapidly, as well as levels of CD89-IgA, IgG-IgA, sCD89, and Gd-IgA1 biomarkers. After discontinuation of IA, proteinuria increased as well as IgG-IgA complexes whereas sCD89-IgA and sCD89 remained low. Further re-intensification of IA and addition of cyclophosphamide improved proteinuria again with reduced IgG-IgA. A second biopsy was performed showing a reduction of extracapillary proliferation to 6% of glomeruli and only 9% glomerulsoclerosis.

CONCLUSIONS

In conclusion, sequential biomonitoring of Gd-IgA1, IgA-immune complexes, and sCD89 in cIgAN was found to be valuable, by correlating with clinical features and glomerular proliferative lesions in cIgAN. These biomarkers could represent useful tools to evaluate kidney injury without repeat kidney biopsies.

Serum immunoglobulin profiles in Chinese children with Henoch-Schönlein purpura

OBJECTIVE

The present study focuses on the associations of serum immunoglobulin with disease activity, relapse/recurrence and renal involvement in Henoch-Schönlein purpura (HSP) children.

METHODS

1683 Chinese children with HSP were recruited from January 2015 to January 2021. Laboratory data of blood samples and urine tests were collected. Renal biopsy was performed by the percutaneous technique. Patients' histories associated with HSP onset were obtained by interviews and questionnaires.

RESULTS

(1) IgA and IgE were dramatically elevated in HSP patients as compared with their normal values, and subject to a 1.75-3.09 fold and a 1.97-2.61 fold increase, respectively. (2) No significant correlation of the disease activity with IgA and IgE was determined, respectively. (3) The serum IgA levels were significantly lower in patients with relapse/recurrence than that in patients without relapse/recurrence, which may be attributed to the transmission of IgA-mediated immune complexes from blood to vessel walls. (4) No significant correlation was found between serum IgA, IgE levels and the pathological classification.

CONCLUSIONS

HSP children have marked disorders of serum immunoglobulin profiles, characterized by significant increases in IgA and IgE. The detection of serum IgA may be applicable to predict relapse/recurrence of HSP, whereas not associated with disease activity and renal involvement.

Urinary Protein Array Analysis to Identify Key Inflammatory Markers in Children with IgA Vasculitis Nephritis

Chronic kidney disease is a recognised complication of immunoglobulin A vasculitis, (IgAV; formerly Henoch–Schonlein purpura—HSP). The pathophysiology of IgAV and why some patients develop significant renal involvement remains largely unknown. Identifying urinary inflammatory markers could direct targets for earlier intervention. The aim of this cross-sectional exploratory study was to perform a large protein array analysis to identify urinary markers to provide insight into the mechanisms of kidney inflammation in children with established IgAV nephritis (IgAVN). Determination of the relative levels of 124 key proteins was performed using commercially available proteome profiler array kits. Twelve children were recruited: IgAVN, n = 4; IgAV without nephritis (IgAVwoN), n = 4; healthy controls (HCs), n = 4. The urinary concentrations of twenty proteins were significantly different in IgAVN compared to IgAVwoN. The largest fold changes were reported for B-cell activating factor (BAFF), Cripto-1, sex-hormone-binding globulin and angiotensinogen. The urinary levels of complement components C5/C5a and factor D were also significantly elevated in patients with IgAVN. A total of 69 urinary proteins significantly raised levels in comparisons made between IgAVN vs. HCs and nine proteins in IgAVwoN vs. HCs, respectively. This study identified key urinary proteins potentially involved in IgAVN providing new insight into the pathophysiology. Further longitudinal studies with larger cohorts are needed to quantitatively analyse these biomarkers.

IgA vasculitis with nephritis: update of pathogenesis with clinical implications

IgA vasculitis with nephritis (IgAVN) shares many pathogenetic features with IgA nephropathy (IgAN). The purpose of this review is to describe our current understanding of the pathogenesis of pediatric IgAVN, particularly as it relates to the four-hit hypothesis for IgAN. These individual steps, i.e., hits, in the pathogenesis of IgAN are (1) elevated production of IgA1 glycoforms with some O-glycans deficient in galactose (galactose-deficient IgA1; Gd-IgA1), (2) generation of circulating IgG autoantibodies specific for Gd-IgA1, (3) formation of pathogenic circulating Gd-IgA1-containing immune complexes, and (4) kidney deposition of the Gd-IgA1-IgG immune complexes from the circulation and induction of glomerular injury. Evidence supporting the four-hit hypothesis in the pathogenesis of pediatric IgAVN is detailed. The genetics, pediatric outcomes, and kidney histopathologic features and the impact of these findings on future treatment and potential biomarkers are discussed. In summary, the evidence points to the critical roles of Gd-IgA1-IgG immune complexes and complement activation in the pathogenesis of IgAVN. Future studies are needed to characterize the features of the immune and autoimmune responses that enable progression of IgA vasculitis to IgAVN.

A Review of the Mechanism of Vascular Endothelial Injury in Immunoglobulin A Vasculitis

Immunoglobulin A (IgA) vasculitis (IgAV), also known as Henoch-Schönlein purpura, is the most common form of childhood vasculitis. It is characterized by cutaneous hemorrhage, resulting from red blood cell leakage into the skin or mucosae, possibly caused by damage to small blood vessels. These acute symptoms usually disappear without treatment. Endothelial cells are distributed on the inner surfaces of blood vessels and lymphatic vessels, and have important functions in metabolism and endocrine function, as well as being the primary targets of external stimuli and endogenous immune activity. Injury to endothelial cells is a feature of IgA vasculitis. Endothelial cell damage may be related to the deposition of immune complexes, the activation of complement, inflammatory factors, and chemokines, oxidative stress, hemodynamics, and coagulation factors. Both epigenetic mechanisms and genetic diversity provide a genetic background for endothelial cell injury. Here, research on the role of endothelial cells in allergic IgA vasculitis is reviewed.

New Insights and Challenges Associated With IgA Vasculitis and IgA Vasculitis With Nephritis-Is It Time to Change the Paradigm of the Most Common Systemic Vasculitis in Childhood?

What are the challenges ahead and how have we responded so far when it comes to the non-granulomatous systemic vasculitis, characterized mainly by deposits of IgA immune complexes in the endothelium of small blood vessels-IgA vasculitis (IgAV)? That is the question to which we tried to answer. We summarized existing knowledge about epidemiology, pathogenesis, genetics, diagnostic tests and therapy in this somewhat neglected entity in pediatric rheumatology. Since etiopathogenesis of IgA vasculitis is complex, with factors other than galactose-deficient IgA₁-containing immune complexes also being important, and may involve numerous interactions between environmental and genetic factors, genomics alone cannot explain the entirety of the risk for the disease. The incidence of IgAV and nephritis varies worldwide and may be a consequence of overlapping genetic and environmental factors. In addition to the role of the HLA class II genes, some studies have pointed to the importance of non-HLA genes, and modern geostatistical research has also indicated a geospatial risk distribution, which may suggest the strong influence of different environmental factors such as climate, pathogen load, and dietary factors. The application of modern geostatistical methods until recently was completely unknown in the study of this disease, but thanks to the latest results it has been shown that they can help us a lot in understanding epidemiology and serve as a guide in generating new hypotheses considering possible environmental risk factors and identification of potential genetic or epigenetic diversity. There is increasing evidence that an integrative approach should be included in the understanding of IgA vasculitis, in terms of the integration of genomics, proteomics, transcriptomics, and epigenetics. This approach could result in the discovery of new pathways important for finding biomarkers that could stratify patients according to the risk of complications, without an invasive kidney biopsy which is still the gold standard to confirm a diagnosis of nephritis, even if biopsy findings interpretation is not uniform in clinical practice. Ultimately, this will allow the development of new therapeutic approaches, especially important in the treatment of nephritis, for which there is still no standardized treatment.

Pathogenesis of IgA Vasculitis: An Up-To-Date Review

Immunoglobin A (IgA) vasculitis (IgAV), formerly called the Henoch-Schönlein purpura (HSP), is a small vessel vasculitis, characterized by IgA1-dominant immune deposition at diseased vessel walls. IgAV is the most common form of vasculitis in children; typical symptoms include palpable purpura, arthritis or arthralgia, abdominal pain, and hematuria or proteinuria. Galactose-deficient IgA1 is detected in the tissues of the kidney and skin in patients with IgAV; it forms immune complexes leading to subsequent immune reactions and injuries. This report provides the recent advances in the understanding of environmental factors, genetics, abnormal innate and acquired immunity, and the role of galactose-deficient IgA1 immunocomplexes in the pathogenesis of IgAV.

Predictive Value of Laboratory Indexes on Renal Involvement in Children with Henoch-Schönlein Purpura

Objective

Henoch-Schönlein purpura (HSP) is the most common vasculitis in children. Renal involvement is the main long-term complication of HSP, and presently there is no way to predict which children may have irreversible renal damage from the outset. This study aimed to explore the prediction value of laboratory indexes on renal involvement in children with HSP, which could help the early identification and intervention.

Methods

Children with HSP hospitalized at the First Affiliated Hospital of Henan University of Chinese Medicine from June 2019 to December 2020 were included. The demographic findings, clinical features, laboratory findings including blood routine examination, serum immunoglobulin, complement, T cell subsets levels, liver and kidney function, coagulation function were recorded. Laboratory indexes were analyzed, logistic regression analysis was performed to identify the independent predictors in HSP patients with renal involvement, and receiver operating characteristic (ROC) curves were further used to assess the value of prediction indexes, as well as the efficacy of combined diagnosis.

Results

The study included 146 HSP patients, among them, 50 patients (34.2%) had renal involvement. Age, platelet distribution width (PDW), CD3⁺ and fibrinogen (FIB) were positively correlated with renal involvement, while the levels of Immunoglobulin G (IgG), C-reactive protein (CRP), and neutrophil/lymphocyte ratio (NLR) were negatively correlated with renal involvement. The area under the ROC Curve (AUC) of these biomarkers ranged from 0.6284 to 0.7009, and among the combinations, a combination of NLR, CRP, CD3⁺, FIB, PDW, IgG and age had the best AUC value (0.9774).

Conclusion

Age, PDW, CD3⁺, FIB, CRP, NLR and IgG were prediction indexes for renal involvement in HSP patients, and these indexes can be combined appropriately to improve the diagnostic efficacy.

Soluble CD89 is a critical factor for mesangial proliferation in childhood IgA nephropathy

Childhood IgA nephropathy (IgAN) includes a wide spectrum of clinical presentations, from isolated hematuria to acute nephritis with rapid loss of kidney function. IgAN is an autoimmune disease and its pathogenesis involves galactose deficient (Gd) IgA1, IgG anti-Gd-IgA1 autoantibodies and the soluble IgA Fc receptor (CD89). However, implication of such factors, notably soluble CD89, in childhood IgAN pathogenesis remains unclear. Here, we studied these biomarkers in a cohort of 67 patients with childhood IgAN and 42 pediatric controls. While Gd-IgA1 was only moderately increased in patient plasma, levels of circulating IgA complexes (soluble CD89-IgA and IgG-IgA) and free soluble CD89 were markedly increased in childhood IgAN. Soluble CD89-IgA1 complexes and free soluble CD89 correlated with proteinuria, as well as histological markers of disease activity: mesangial, endocapillary hypercellularity and cellular crescents. Soluble CD89 was found in patient's urine but not in urine from pediatric controls. Mesangial deposits of soluble CD89 were detected in biopsies from patients with childhood IgAN. Serum chromatographic fractions containing covalently linked soluble CD89-IgA1 complexes or free soluble CD89 from patients induced mesangial cell proliferation in vitro in a soluble CD89-dependent manner. Recombinant soluble CD89 induced mesangial cell proliferation in vitro which was inhibited by free soluble recombinant CD71 (also a mesangial IgA receptor) or mTOR blockers. Interestingly, injection of recombinant soluble CD89 induced marked glomerular proliferation and proteinuria in mice expressing human IgA1. Thus, free and IgA1-complexed soluble CD89 are key players in mesangial proliferation. Hence, our findings suggest that soluble CD89 plays an essential role in IgAN pathogenesis making it a potential biomarker and therapeutic target.

IgA Vasculitis with Nephritis in Adults: Histological and Clinical Assessment

Patients with IgA vasculitis (IgAV), an immune complex-mediated disease, may exhibit kidney involvement-IgAV with nephritis (IgAVN). The kidney-biopsy histopathologic features of IgAVN are similar to those of IgA nephropathy, but little is known about histopathologic disease severity based on the interval between purpura onset and diagnostic kidney biopsy. We assessed kidney histopathology and clinical and laboratory data in a cohort of adult patients with IgAVN (n = 110). The cases were grouped based on the interval between the onset of purpura and kidney biopsy: Group 1 (G1, <1 month, n = 14), Group 2 (G2, 1-6 months, n = 58), and Group 3 (G3, >6 months, n = 38). Glomerular leukocytes were more common in G1 than in the other groups (p = 0.0008). The proportion of neutrophils among peripheral-blood leukocytes was the highest in the patients biopsied within a month after onset of purpura (G1: 71 ± 8%). In the patients with an interval >6 months, the neutrophil proportion was lower, 60%. Moreover, the glomerular mesangial proliferation score correlated with the serum total IgA concentration (p = 0.0056). In conclusion, IgAVN patients biopsied <1 month from purpura onset showed an elevated percentage of blood neutrophils and glomerular leukocytes, consistent with an acute-onset inflammatory reaction. In all IgAVN patients, the mesangial proliferation score correlated with the serum IgA level.

Intermittent abdominal pain in IgA vasculitis

Objective:

To assess intermittent abdominal pain in IgA vasculitis patients and its relation to demographic data, clinical manifestations and treatments.

Methods:

A retrospective cohort study included 322 patients with IgA vasculitis (EULAR/PRINTO/PRES criteria) seen at the Pediatric Rheumatology Unit in the last 32 years. Sixteen patients were excluded due to incomplete data in medical charts. Intermittent abdominal pain was characterized by new abdominal pain after complete resolution in the first month of disease.

Results:

Intermittent abdominal pain was observed in 35/306 (11%) IgA vasculitis patients. The median time between first and second abdominal pain was 10 days (3–30 days). The main treatment of intermittent abdominal pain included glucocorticoid [n=26/35 (74%)] and/or ranitidine [n=22/35 (63%)]. Additional analysis showed that the frequency of intermittent purpura/petechiae (37 vs. 21%; p=0.027) and the median of purpura/petechiae duration [20 (3–90) vs. 14 (1–270) days; p=0.014] were significantly higher in IgA vasculitis patients with intermittent abdominal pain compared to those without. Gastrointestinal bleeding (49 vs. 13%; p<0.001), nephritis (71 vs. 45%; p=0.006), glucocorticoid (74 vs. 44%; p=0.001) and intravenous immunoglobulin use (6 vs. 0%; p=0.036) were also significantly higher in the former group. The frequency of ranitidine use was significantly higher in IgA vasculitis patients with intermittent abdominal pain versus without (63 vs. 28%; p<0.001), whereas the median of ranitidine duration was reduced in the former group [35 (2–90) vs. 60 (5–425) days; p=0.004].

Conclusions:

Intermittent abdominal pain occurred in nearly a tenth of IgA vasculitis patients, in the first 30 days of disease, and was associated with other severe clinical features. Therefore, this study suggests that these patients should be followed strictly with clinical and laboratorial assessment, particularly during the first month of disease course.

IgA vasculitis nephritis in children and adults: one or different entities?

The clinical features of the kidney involvement in immunoglobulin A (IgA) vasculitis (IgAVN) differ in children and adults for both clinical presentation and progression. IgAVN in children has mostly a self-limiting course and favorable resolution, while in adults the kidney involvement is frequently severe with unfavorable outcome. However, a subset of children is at risk of progression within the pediatric age or decades later in adulthood, particularly when the diagnosis and a prompt intervention are delayed. Factors predicting progression and outcome in the whole spectrum of age have been investigated in recent research, as well as the relationship between IgAVN and primary IgAN, which share the same pathology features, in the light of peculiar clinical differences and progression tendencies, and hence need for selective treatments. The search for a personalized treatment in children with IgAV and in different ages of life should rely on the identification of different risks for progression. This review will focus on recent studies which contribute to improve our knowledge in this still largely unclear area.

IgA Vasculitis: Etiology, Treatment, Biomarkers and Epigenetic Changes

IgA, previously called Henoch-Schönlein vasculitis, is an essential immune component that drives the host immune response to the external environment. As IgA has the unique characteristic of a flexible response to broad types of microorganisms, it sometimes causes an autoreactive response in the host human body. IgA vasculitis and related organ dysfunction are representative IgA-mediated autoimmune diseases; bacterial and viral infections often trigger IgA vasculitis. Recent drug developments and the presence of COVID-19 have revealed that these agents can also trigger IgA vasculitis. These findings provide a novel understanding of the pathogenesis of IgA vasculitis. In this review, we focus on the characteristics of IgA and symptoms of IgA vasculitis and other organ dysfunction. We also mention the therapeutic approach, biomarkers, novel triggers for IgA vasculitis, and epigenetic modifications in patients with IgA vasculitis.

MicroRNA profiling in Chinese children with Henoch-Schonlein purpura and association between selected microRNAs and inflammatory biomarkers

AIM

This study aimed to profile the microRNA levels in Chinese Henoch-Schonlein purpura (HSP) children and to explore their association with inflammatory factors and T helper 17 (Th17)/regulatory T (Treg).

METHODS

Forty-five HSP children and 27 healthy controls were enrolled in this study, and microRNA levels were profiled with a microRNA microarray. The levels of selected microRNAs were determined by quantitative real-time PCR, and the levels of serum IgA, interleukin-6, interleukin-10 and interleukin-17A were detected by enzyme-linked immunosorbent assay. Additionally, Th17 and Treg cells were analysed by flow cytometry.

RESULTS

There were 9 up-regulated and 27 down-regulated microRNAs in the PBMCs of Chinese HSP children. Among them, miR-1-3p, miR-19b-1-5p and miR-29b-1-5p were up-regulated, while miR-483-5p and miR-1246 were down-regulated. Additionally, these selected microRNAs could differentiate HSP patients from healthy controls. Interestingly, miR-29b-1-5p was correlated with IgA, miR-19b-1-5p, miR-483-5p and miR-1246 were correlated with interleukin-6, while miR-1-3p and miR-1246 were correlated with Th17/Treg.

CONCLUSION

This study reveals that the altered microRNAs could differentiate HSP from the healthy, and were associated with inflammatory factors or Th17/Treg. It is indicated that alteration in these microRNAs may contribute to the HSP pathogenesis and may become therapeutic targets or diagnostic biomarkers for HSP.

Gastrointestinal involvement and its association with the risk for nephritis in IgA vasculitis

Background:

We analysed clinical and biochemical parameters in predicting severe gastrointestinal (GI) manifestations in childhood IgA vasculitis (IgAV) and the risk of developing renal complications.

Methods:

A national multicentric retrospective study included children with IgAV reviewed in five Croatian University Centres for paediatric rheumatology in the period 2009–2019.

Results:

Out of 611 children, 281 (45.99%) had at least one GI manifestation, while 42 of 281 (14.95%) had the most severe GI manifestations. Using logistic regression several clinical risk factors for the severe GI manifestations were identified: generalized rash [odds ratio (OR) 2.09 (95% confidence interval (CI) 1.09–4.01)], rash extended on upper extremities (OR 2.77 (95% CI 1.43–5.34)] or face [OR 3.69 (95% CI 1.42–9.43)] and nephritis (IgAVN) [OR 4.35 (95% CI 2.23–8.50)], as well as lower values of prothrombin time (OR 0.05 (95% CI 0.01–0.62)], fibrinogen [OR 0.45 (95% CI 0.29–0.70)] and IgM [OR 0.10 (95% I 0.03–0.35)]] among the laboratory parameters. Patients with severe GI involvement more frequently had relapse of the disease [OR 2.14 (CI 1.04–4.39)] and recurrent rash [OR 2.61 (CI 1.27–5.38)]. Multivariate logistic regression found that the combination of age, GI symptoms at the beginning of IgAV and severity of GI symptoms were statistically significant predictors of IgAVN. Patients in whom IgAV has started with GI symptoms [OR 6.60 (95% CI 1.67–26.06)], older children [OR 1.22 (95% CI 1.02–1.46)] with severe GI form of IgAV (OR 5.90 (95% CI 1.12–31.15)] were particularly high-risk for developing IgAVN.

Conclusion:

We detected a group of older children with the onset of GI symptoms before other IgAV symptoms and severe GI form of the IgAV, with significantly higher risk for acute and chronic complications of IgAV.

IgA vasculitis

IgA vasculitis (IgAV) is an inflammation of small vessels caused by perivascular deposition of IgA and activation of neutrophils. It may present as systemic vasculitis (IgAV - Henoch-Schönlein purpura) or as a variant restricted to the skin (skin-limited IgAV), while IgA nephropathy presents a variant restricted to the kidneys. Systemic IgAV affects children more frequently than adults (150 to 200 for 1; incidence 1 in 1 million/year). In the latter, disease more often leads to chronic renal disease. The dominant clinical features include round or oval and retiform palpable purpura predominantly on the lower legs, arthralgia or arthritis, gastrointestinal bleeding or pain and glomerulonephritis with mesangial IgA deposits (IgAVN). Pulmonary, cardiac, genital and neurological involvement occurs, but is rare. Immune complexes containing galactose-deficient IgA1 play a pivotal role in the pathophysiology of IgAV; via the Fc alpha receptor (CD89), they induce neutrophilic inflammation around cutaneous vessels and mesangial proliferation and inflammation in the glomerulus. In case of self-limited disease, only symptomatic treatment is recommended. Treatment of severe IgAV, nephritis or gastrointestinal manifestations, is not established, but some studies reported a benefit of corticosteroids, combined with immunosuppressive drugs. Short-term outcome depends on the severity of gastrointestinal manifestations, while long-term prognosis depends on the severity of nephritis.

IgA Vasculitis and IgA Nephropathy: Same Disease?

Many authors suggested that IgA Vasculitis (IgAV) and IgA Nephropathy (IgAN) would be two clinical manifestations of the same disease; in particular, that IgAV would be the systemic form of the IgAN. A limited number of studies have included sufficient children or adults with IgAN or IgAV (with or without nephropathy) and followed long enough to conclude on differences or similarities in terms of clinical, biological or histological presentation, physiopathology, genetics or prognosis. All therapeutic trials available on IgAN excluded patients with vasculitis. IgAV and IgAN could represent different extremities of a continuous spectrum of the same disease. Due to skin rash, patients with IgAV are diagnosed precociously. Conversely, because of the absence of any clinical signs, a renal biopsy is practiced for patients with an IgAN to confirm nephropathy at any time of the evolution of the disease, which could explain the frequent chronic lesions at diagnosis. Nevertheless, the question that remains unsolved is why do patients with IgAN not have skin lesions and some patients with IgAV not have nephropathy? Larger clinical studies are needed, including both diseases, with a common histological classification, and stratified on age and genetic background to assess renal prognosis and therapeutic strategies.

Rare Collagenous Heterozygote Variants in Children With IgA Nephropathy

Introduction

Childhood IgA nephropathy (cIgAN) is a primary glomerulonephritis clinically characterized by microscopic hematuria and proteinuria, the presence of which may potentially overlap with Alport syndrome. Interestingly, earlier studies suggested that familial IgAN could be linked to the chromosome 2q36 region, also the coding region for collagen type 4 alpha 3/4 (COL4A3/A4).

Methods

To investigate a possible relationship or phenocopy between Alport syndrome and cIgAN, COL4A3, COL4A4, and COL4A5 exons were sequenced in 36 cIgAN patients. Clinical data and treatment were collected retrospectively. COL4A3/A4/A5 variants were classified according to American College of Medical Genetics and the Association for Molecular Pathology (ACMG/AMP) guidelines.

Results

Four of 36 cIgAN patients were affected by ACMG class 4/5 COL4A3 heterozygous variants (COL4A3-cIgAN). We found no COL4A4 or COL4A5 variant. Despite having rare and deleterious COL4A3 variants, 3 of 4 COL4A3-cIgAN children developed clinical and biologic features of active IgAN rather than Alport syndrome. Response to intensive immunosuppressive treatment was favorable, leading to a reduction of endocapillary and extracapillary proliferation lesions. High levels of immune immunoglobulin G and A (IgG/IgA) complexes, reduction of proteinuria, and gradual stabilization of estimated glomerular filtration rate (eGFR) argued against Alport syndrome. Nevertheless, COL4A3-cIgAN patients seemed predisposed to a more serious IgAN presentation compared with the non‒COL4A3-cIgAN group, with more glomerulosclerosis and a lower eGFR over time. One of the 4 patients underwent kidney transplant with subsequent IgAN recurrence.

Conclusions

Predisposition factors for developing serious cIgAN flare-up should be considered for cIgAN with COL4A3 pathologic heterozygous variants. COL4A3 variants, usually responsible for Alport syndrome in adults, should not automatically exclude an immunosuppressive regimen in cIgAN. Moreover, evidence of an ACMG class 4/5 COL4A3 variant in early-stage cIgAN could be a helpful tool for stratifying severity of cIgAN beyond the Oxford classification.

Proteomic analysis of urine reveals biomarkers for the diagnosis and phenotyping of abdominal-type Henoch-Schonlein purpura

BACKGROUND

Abdominal-type Henoch-Schonlein purpura (HSP) is a common refractory disease in children. Currently, no specific diagnostic biomarker is available for HSP.

METHODS

Children with abdominal type HSP were first diagnosed with three syndromes using Chinese traditional medicine. The urinary proteomes among the three syndromes of patients with abdominal type HSP and healthy controls were compared using two label-free proteomics quantifications, including data-dependent acquisition and data-independent acquisition.

RESULTS

For the comparison between patients with abdominal type HSP and healthy children, a total of 75 differential urinary proteins were identified by determining the overlap of the two experiments. The ingenuity pathway analysis (IPA) analysis showed that these differential proteins were correlated with the pathogenesis of abdominal type HSP. Of these, 37 proteins were distributed in 13 solid tissues as tissue-enriched proteins. Monitoring changes in these proteins might help us detect uncommon clinical manifestations of HSP. Patients with abdominal type HSP can be further distinguished into three syndromes based on the urine proteome. Finally, a panel of six urinary proteins (P25774, P09417, Q7Z5L0, P60900, P14550 and P09668) was constructed for both the diagnosis and phenotyping of abdominal type HSP.

CONCLUSIONS

Urinary protein biomarkers for the diagnosis and phenotyping of abdominal type HSP were identified, which will contribute to the personalized treatment of patients with abdominal type HSP.

Aberrant RL2 O-GlcNAc antibody reactivity against serum-IgA1 of patients with colorectal cancer

O-GlcNAcylation, a single attachment of N-acetylglucosamine (GlcNAc) on serine and threonine residues, plays important roles in normal and pathobiological states of many diseases. Aberrant expression of O-GlcNAc modification was found in many types of cancer including colorectal cancer (CRC). This modification mainly occurs in nuclear-cytoplasmic proteins; however, it can exist in some extracellular and secretory proteins. In this study, we investigated whether O-GlcNAc-modified proteins are present in serum of patients with CRC. Serum glycoproteins of CRC patients and healthy controls were enriched by wheat germ agglutinin, a glycan binding protein specifically binds to terminal GlcNAc and sialic acid. Two-dimensional gel electrophoresis, RL2 O-GlcNAc immunoblotting, affinity purification, and mass spectrometry were performed. The results showed that RL2 O-GlcNAc antibody predominantly reacted against serum immunoglobulin A1 (IgA1). The levels of RL2-reacted IgA were significantly increased while total IgA were not different in patients with CRC compared to those of healthy controls. Analyses by ion trap mass spectrometry using collision-induced dissociation and electron-transfer dissociation modes revealed one O-linked N-acetylhexosamine modification site at Ser₂₆₈ located in the heavy constant region of IgA1; unfortunately, it cannot be discriminated whether it was N-acetylglucosamine or N-acetylgalactosamine because of their identical molecular mass. Although failed to demonstrate unequivocally it was O-GlcNAc, these data indicated that serum-IgA had an aberrantly increased reactivity against RL2 O-GlcNAc antibody in CRC patients. This specific glycosylated form of serum-IgA1 will expand the spectrum of aberrant glycosylation which provides valuable information to cancer glycobiology.

Immunoglobulin A Glycosylation and Its Role in Disease

Human IgA is comprised of two subclasses, IgA1 and IgA2. Monomeric IgA (mIgA), polymeric IgA (pIgA), and secretory IgA (SIgA) are the main molecular forms of IgA. The production of IgA rivals all other immunoglobulin isotypes. The large quantities of IgA reflect the fundamental roles it plays in immune defense, protecting vulnerable mucosal surfaces against invading pathogens. SIgA dominates mucosal surfaces, whereas IgA in circulation is predominately monomeric. All forms of IgA are glycosylated, and the glycans significantly influence its various roles, including antigen binding and the antibody effector functions, mediated by the Fab and Fc portions, respectively. In contrast to its protective role, the aberrant glycosylation of IgA1 has been implicated in the pathogenesis of autoimmune diseases, such as IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN). Furthermore, detailed characterization of IgA glycosylation, including its diverse range of heterogeneity, is of emerging interest. We provide an overview of the glycosylation observed for each subclass and molecular form of IgA as well as the range of heterogeneity for each site of glycosylation. In many ways, the role of IgA glycosylation is in its early stages of being elucidated. This chapter provides an overview of the current knowledge and research directions.