IgA vasculitis with nephritis: update of pathogenesis with clinical implications

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.

Exploration of the pathogenesis of nephrotic syndrome and traditional Chinese medicine intervention based on gut microbiota

Nephrotic syndrome (NS) represents a prevalent syndrome among various chronic kidney disease pathologies and is known for its higher severity and worse prognosis compared with chronic glomerulonephritis. Understanding its pathogenesis and identifying more effective treatment modalities have long been a concern of kidney specialists. With the introduction of the gut-kidney axis concept and the progress in omics technologies, alterations in the gut microbiota have been observed in primary and secondary NS. This link has been extensively researched in conditions such as diabetic nephropathy and immunoglobulin A (IgA) nephropathy. Thus, dysbiosis of the gut microbiota is seen as a crucial contributing factor in NS; however, there is a lack of comprehensive reviews that elucidate the changes in the gut microbiota across different NS conditions and that describe its mechanistic role in the disease. Moreover, serving as an innate regulator of the gut microbiota, traditional Chinese medicine (TCM) has the potential to exert a profound impact on the expression of inflammation-promoting agents, decreasing the levels of endotoxins and uremic toxins. In addition, it strengthens the stability of the intestinal barrier while controlling the metabolic function of the body through its efficient modulation of the gut microbiota. This intricate process yields far-reaching consequences for NS.

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.

IgA Vasculitis (Henoch-Schönlein Purpura): An Update on Treatment

Objective: IgA vasculitis (IgAV), previously named as Henoch-Schönlein purpura, is the most frequent systemic vasculitis in children. In adults, IgAV is less common although it is associated with more severe disease. In fact, the frequency of glomerulonephritis (referred to as IgAV nephritis) in adults is higher than in children and tends to present more severely, with around 10-30% of those affected eventually progressing to end-stage renal disease. In this review, we describe the pathophysiology, main clinical features, diagnosis of the disease, and latest clinical data regarding IgAV therapy. Methods: A narrative literature review, primarily based on articles published in PubMed, was conducted. In addition to discussing the main aspects of glucocorticoids and conventional disease-modifying drugs used in the management of IgAV, this review focuses on the latest information reported regarding biologics and potential future therapies. Results: Glucocorticoids are the first-line therapy for IgAV, especially in adults with severe manifestations. Colchicine, dapsone, and methotrexate can be useful for controlling minor manifestations. Several immunomodulatory agents, such as cyclosporine A, tacrolimus, and mycophenolate mofetil, have shown favorable results as glucocorticoid-sparing agents. Leflunomide has shown promising results but requires further study. The use of rituximab has demonstrated efficacy in reducing relapse frequency, lowering the cumulative glucocorticoid burden, and achieving long-term remission of the disease in children and adults with IgAV. Immunoglobulins and plasma exchange therapy can also be useful in difficult and life-threatening situations. Other potential therapies with encouraging results include TRF-budesonide, B-cell-directed therapy, B-cell-depleting agents, sodium-glucose cotransporter-2 inhibitors, endothelin receptor antagonists, and complement pathway inhibitors. Conclusions: Glucocorticoids are the first-line therapy for IgAV, especially in adults with severe manifestations. The role of various immunomodulatory therapies, such as calcineurin inhibitors and mycophenolate mofetil, remains promising, while rituximab reduces the long-term side effects of glucocorticoids and can help achieve disease remission. Other potential therapies with encouraging results require further research.

O-glycosylation of IgA1 and the pathogenesis of an autoimmune disease IgA nephropathy

IgA nephropathy is a kidney disease characterized by deposition of immune complexes containing abnormally O-glycosylated IgA1 in the glomeruli. Specifically, some O-glycans are missing galactose that is normally β1,3-linked to N-acetylgalactosamine of the core 1 glycans. These galactose-deficient IgA1 glycoforms are produced by IgA1-secreting cells due to a dysregulated expression and activity of several glycosyltransferases. Galactose-deficient IgA1 in the circulation of patients with IgA nephropathy is bound by IgG autoantibodies and the resultant immune complexes can contain additional proteins, such as complement C3. These complexes, if not removed from the circulation, can enter the glomerular mesangium, activate the resident mesangial cells, and induce glomerular injury. In this review, we briefly summarize clinical and pathological features of IgA nephropathy, review normal and aberrant IgA1 O-glycosylation pathways, and discuss the origins and potential significance of natural anti-glycan antibodies, namely those recognizing N-acetylgalactosamine. We also discuss the features of autoantibodies specific for galactose-deficient IgA1 and the characteristics of pathogenic immune complexes containing IgA1 and IgG. In IgA nephropathy, kidneys are injured by IgA1-containing immune complexes as innocent bystanders. Most patients with IgA nephropathy progress to kidney failure and require dialysis or transplantation. Moreover, most patients after transplantation experience a recurrent disease. Thus, a better understanding of the pathogenetic mechanisms is needed to develop new disease-specific treatments.

The Journey to Advocacy: Celebrating the IgA Nephropathy Foundation's 20th Anniversary

The IgA Nephropathy Foundation was established in 2004 by Bonnie and Ed Schneider, the concerned parents of a young boy diagnosed with IgA nephropathy (IgAN). At the time the Foundation was established, patients had trouble finding the most basic information about IgAN, and few nephrologists had experience with this rare disease. Celebrating its 20th anniversary this year, the Foundation has been instrumental in bringing the IgAN community together through research grants, advocating for patients and caregivers, offering patient support services, and becoming the go-to source for information and education. A big focus for the Foundation is communicating the "voice of the patient" to the medical community to help identify needs and provide insight into the lives of IgAN patients and caregivers. The Foundation is very active in getting the word out, attending the last two International Symposia on IgA Nephropathy, in Prague, Czech Republic, and Tokyo, Japan. The Foundation also sponsored the IgA Nephropathy Seminar Day at the 6th CKD Summit in Boston in spring 2024. This article chronicles some of the Foundation's key milestones, highlights patient-facing and point-of-care resources, and provides key insights into the patient experience as well as tips for how clinicians can best meet patients where they are, bridge gaps, and improve care. The unmet needs of the IgAN community continue to drive the IgA Nephropathy Foundation's purpose and steadfast commitment to finding a cure for this rare disease.

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.

Preclinical Detection of Early Glomerular Injury in Children with Kidney Diseases-Independently of Usual Markers of Kidney Impairment and Inflammation

Glomerular kidney diseases typically begin insidiously and can progress to end stage kidney failure. Early onset of therapy can slow down disease progression. Early diagnosis is required to ensure such timely therapy. The goal of our study was to evaluate protein biomarkers (BMs) for common nephropathies that have been described for children with Alport syndrome. Nineteen candidate BMs were determined by commercial ELISA in children with congenital anomalies of the kidneys and urogenital tract, inflammatory kidney injury, or diabetes mellitus. It is particularly essential to search for kidney disease BMs in children because they are a crucial target group that likely exhibits early disease stages and in which misleading diseases unrelated to the kidney are rare. Only minor differences in blood between affected individuals and controls were found. However, in urine, several biomarker candidates alone or in combination seemed to be promising indicators of renal injury in early disease stages. The BMs of highest sensitivity and specificity were collagen type XIII, hyaluronan-binding protein 2, and complement C4-binding protein. These proteins are unrelated to inflammation markers or to risk factors for and signs of renal failure. In conclusion, our study evaluated several strong candidates for screening for early stages of kidney diseases and can help to establish early nephroprotective regimens.

Analysis of the influencing factors of abdominal Henoch-Schonlein purpura in children with gastrointestinal bleeding and the clinical value of PLR

OBJECTIVE

To identify the influencing factors of gastrointestinal bleeding in children with abdominal-type Henoch-Schonlein purpura (HSP) and to assess the diagnostic value of PLR (platelet-to-lymphocyte ratio).

METHODS

We retrospectively analyzed the medical records of 112 children with abdominal HSP admitted to Northwest Women's and Children's Hospital from April 2021 to May 2023. Among them, 62 cases with gastrointestinal bleeding constituted the bleeding group, while the other 50 cases without gastrointestinal bleeding comprised the non-bleeding group. We compared PLR and related routine blood indicators between the two groups. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors for gastrointestinal bleeding. HSP children with gastrointestinal bleeding were further categorized based on treatment efficacy, and the predictive value of PLR for treatment efficacy was analyzed.

RESULTS

The observation group exhibited significantly higher levels of WBC, NEU, PLT, MPV, C-reactive protein, and PLR, along with lower lymphocyte levels compared to the control group (all P < 0.05). Univariate analysis revealed associations between symptom onset, abdominal pain, vomiting, levels of WBC, NEU, LYM, PLT, PLR, C-reactive protein and gastrointestinal bleeding (all P < 0.05). Multivariate logistic analysis identified onset with abdominal pain, high WBC values, and elevated PLR ratios as risk factors for gastrointestinal bleeding. The ROC curve demonstrated an AUC of 0.914 for PLR in predicting gastrointestinal bleeding. Additionally, PLR was significantly lower in the good efficacy group compared to the poor efficacy group. The AUC of PLR in predicting treatment efficacy was 0.804, indicating high predictive value.

CONCLUSION

Elevated PLR may serve as a potential risk factor for gastrointestinal bleeding in children with abdominal-type allergic purpura. Monitoring changes in PLR could aid in diagnosis and improvements in treatment for this condition.

Navigating Adult-Onset IgA Vasculitis-Associated Nephritis

PURPOSE OF REVIEW

IgA vasculitis (IgAV), formerly Henoch-Schonlein purpura, is the most common systemic vasculitis in childhood. In adults, however, this condition is poorly understood, yet associated with more severe disease and poorer outcomes. This necessitates the need for early diagnosis and management.

SCOPE OF REVIEW

We describe the pathophysiology, clinical manifestations, and diagnosis of IgAV in adults. Poor outcomes are often due to the high frequency of glomerulonephritis in IgAV-IgA vasculitis-associated nephritis (IgAVN). We hence also aim to summarize the latest clinical data regarding treatment strategies in IgAVN. The diagnosis and differentiation in histology between IgAVN and IgA nephropathy (IgAN) remain a challenge. Review of treatment therapies: Pathological mechanisms between IgAVN and IgAN appear to be consistent between the two, and data from IgAN are often extrapolated to IgAVN. The role of various immunosuppression therapies remains controversial, and in this review, we will discuss immunosuppression use and highlight evidence surrounding emerging and promising novel therapies in IgAVN/IgAN. Our aim for this review is to guide future treatment strategies and direct future studies.

Immunoglobulin A vasculitis: The clinical features and pathophysiology

Palpable purpura, gastrointestinal symptoms, joint involvement, and renal disease characterize immunoglobulin A vasculitis (IgAV). Renal involvement ranging from mild proteinuria to severe nephritic or nephrotic syndrome highlights the importance of monitoring kidney function in patients with IgAV. Recognizing these key features is crucial for early diagnosis and appropriate management to prevent long-term complications related to kidney disease. However, the pathogenesis of IgAV remains unclear. Disease mechanisms involve various factors, including the interplay of aberrantly glycosylated IgA, anti-endothelial cell antibodies, and neutrophils following infection triggers, which are the main pathogenic mechanisms of IgAV. Insights from cases of IgAV related to Coronavirus disease 2019 have offered additional understanding of the connection between infection and IgAV pathogenesis. This review provides a valuable resource for healthcare professionals and rheumatology researchers seeking a better understanding of the clinical features and pathophysiology of IgAV.

Sparsentan: the first and only non-immunosuppressive therapy for the reduction of proteinuria in IgA nephropathy

INTRODUCTION

IgA nephropathy is one of the most common forms of glomerular disease. Patients with persistent proteinuria are at increased risk of progression to kidney failure. There is a significant need for safe and effective therapies to lower proteinuria in these patients. Sparsentan is a non-immunosuppressive agent that acts as a dual angiotensin and endothelin receptor antagonist. It lowers proteinuria in experimental models of glomerular disease and in affected patients.

AREAS COVERED

This review covers the immunological and non-immunological actions of sparsentan in glomerular disease. It reviews the clinical trials that evaluated the impact of the drug in pediatric and adult patients with IgA nephropathy. It places the use of sparsentan in an overall treatment paradigm for the full spectrum of patients with IgA nephropathy including nonspecific renoprotective agents such as inhibitors of the renin-angiotensin-aldosterone axis and SGLT2 transporter and immunosuppressive drugs. The review represents a search of the current literature about the effect of the drug on normal physiology and the pathogenesis of IgA nephropathy.

EXPERT OPINION

The safety, tolerability, and therapeutic efficacy of sparsentan have been demonstrated in long-term studies of patients with primary glomerular diseases extending over 5 years. The evidence in support of a beneficial treatment effect of sparsentan is stronger in IgAN than in FSGS. It is anticipated that sparsentan will supplant the use of ACEI or ARB as the first-line therapy to reduce proteinuria prior to the implementation of immunosuppressive agents in patients with IgA nephropathy. It may be combined with other renoprotective drugs like SGLT2 inhibitors. Practice guidelines are needed to promote safe and effective use of this new drug by nephrologists caring for patients with IgAN in all clinical settings.

The Association of HMGB1 and RAGE Gene Polymorphisms with IgA Vasculitis

High-mobility group box 1 (HMGB1) is a pleiotropic cytokine that propagates inflammation by its extracellular action of interacting with the receptor for advanced glycation end products (RAGE). Both HMGB1 and RAGE play multiple roles in the pathogenesis of a variety of inflammatory and autoimmune diseases. We investigated the association of five single-nucleotide polymorphisms (SNPs) of the HMGB1 gene (rs1412125, rs2249825, rs1045411, rs1060348, rs41369348) and four SNPs of the RAGE gene (rs1800624, rs1800625, rs2070600, rs3134940) with the susceptibility and clinical features of paediatric patients with IgA vasculitis (IgAV), also known as Henoch-Schönlein's purpura. This case‒control study included 103 children with IgAV (experimental group) and 150 age-matched healthy individuals (control group). The strength of the association between different groups and alleles or genotypes of HMGB1 and RAGE was estimated using odds ratios (ORs) and 95% confidence intervals (CIs). The HMGB1 polymorphisms rs41369348, rs1045411, rs2249825 and rs1412125 were associated with the development of generalized purpuric rash, and rs1412125 was associated with IgAV nephritis (IgAVN). The RAGE polymorphism rs2070600 might be linked to the development of arthritis in IgAV patients. There was no statistically significant association between the analysed polymorphisms and susceptibility to IgAV. This is the first study to propose an association between several HMGB1 and RAGE polymorphisms and different phenotypes in the clinical course of IgAV in a paediatric population. Further research on other polymorphisms of HMGB1 and RAGE should be conducted in a larger number of patients.

IgA vasculitis nephritis: insights from kidney biopsies

PURPOSE OF REVIEW

To present findings indicating the value of kidney biopsy in assessing prognosis and guiding clinical approach to patients with IgA vasculitis nephritis (IgAVN), including a recent international study examining the value of the Oxford (MEST-C) classification.

RECENT FINDINGS

Historically, kidney biopsies with IgAVN are scored using the International Society for Kidney Diseases in Children (ISKDC) classification. However, this classification has limited prognostic value, and most biopsies fall into just two of the six ISKDC grades. There are few studies examining the clinical value of the Oxford classification, which is well documented to be predictive of kidney outcomes in IgA nephropathy, in IgAVN. However, a recent study of 361 biopsied patients with IgAVN showed that endocapillary hypercellularity (Oxford E1) predicted a subclass of patients showing initial improvement in kidney function with immunosuppressive treatment, followed by a later decline.

SUMMARY

Kidney outcome in patients with biopsied IgAVN treated with immunosuppression is determined by clinical factors and endocapillary hypercellularity. The latter is not part of the ISKDC classification and supports including MEST-C scores in biopsy reports of IgAVN. Even patients showing a good initial response to immunosuppression require long-term follow-up due to risk of subsequent kidney function decline.

A Case Series of Unusual IgA Vasculitis

Introduction

Immunoglobulin A vasculitis (IgA)is a rare condition characterized by palpable purpura, often involving the skin, gastrointestinal tract, joints, and kidneys. Presentation is usually acute and is more common in children and adolescents of Southeast Asian and European descent. In the adult population, it is less common and therapies are not as well-established.

Case Presentation

Disease prevalence of IgA vasculitis outside Southeast Asian and European populations is not well-documented. In this case series, we present 2 cases of IgA vasculitis in 2 older adult males, one of Native American descent and one of African American descent.

Conclusion

IgA vasculitis must be considered within the adult population, and it is not limited to certain ethnic groups. Further research is needed to give clarity on the best treatment options for adults with IgA vasculitis. We believe that patients presenting with IgA vasculitis are best managed in a multidisciplinary approach, especially those patients with limited improvement despite the initiation of corticosteroids. Our 2 cases should raise awareness of IgA vasculitis in patients with skin rashes and elevated creatinine levels.

Histologic and Clinical Factors Associated with Kidney Outcomes in IgA Vasculitis Nephritis

BACKGROUND

Nephritis is a common manifestation of IgA vasculitis and is morphologically indistinguishable from IgA nephropathy. While MEST-C scores are predictive of kidney outcomes in IgA nephropathy, their value in IgA vasculitis nephritis has not been investigated in large multiethnic cohorts.

METHODS

Biopsies from 262 children and 99 adults with IgA vasculitis nephritis ( N =361) from 23 centers in North America, Europe, and Asia were independently scored by three pathologists. MEST-C scores were assessed for correlation with eGFR/proteinuria at biopsy. Because most patients ( N =309, 86%) received immunosuppression, risk factors for outcomes were evaluated in this group using latent class mixed models to identify classes of eGFR trajectories over a median follow-up of 2.7 years (interquartile range, 1.2-5.1). Clinical and histologic parameters associated with each class were determined using logistic regression.

RESULTS

M, E, T, and C scores were correlated with either eGFR or proteinuria at biopsy. Two classes were identified by latent class mixed model, one with initial improvement in eGFR followed by a late decline (class 1, N =91) and another with stable eGFR (class 2, N =218). Class 1 was associated with a higher risk of an established kidney outcome (time to ≥30% decline in eGFR or kidney failure; hazard ratio, 5.84; 95% confidence interval, 2.37 to 14.4). Among MEST-C scores, only E1 was associated with class 1 by multivariable analysis. Other factors associated with class 1 were age 18 years and younger, male sex, lower eGFR at biopsy, and extrarenal noncutaneous disease. Fibrous crescents without active changes were associated with class 2.

CONCLUSIONS

Kidney outcome in patients with biopsied IgA vasculitis nephritis treated with immunosuppression was determined by clinical risk factors and endocapillary hypercellularity (E1) and fibrous crescents, which are features that are not part of the International Study of Diseases of Children classification.

Urinary Protein-Biomarkers Reliably Indicate Very Early Kidney Damage in Children With Alport Syndrome Independently of Albuminuria and Inflammation

Introduction

Alport syndrome (AS) is a hereditary type IV collagen disease. It starts shortly after birth, without clinical symptoms, and progresses to end-stage kidney disease early in life. The earlier therapy starts, the more effectively end-stage kidney disease can be delayed. Clearly then, to ensure preemptive therapy, early diagnosis is an essential prerequisite.

Methods

To provide early diagnosis, we searched for protein biomarkers (BMs) by mass spectrometry in dogs with AS stage 0. At this very early stage, we identified 74 candidate BMs. Of these, using commercial enzyme-linked immunosorbent assays (ELISAs), we evaluated 27 in dogs and 28 in children, 50 with AS and 104 healthy controls.

Results

Most BMs from blood appeared as fractions of multiple variants of the same protein, as shown by their chromatographic distribution before mass spectrometry. Blood samples showed only minor differences because ELISAs rarely detect disease-specific variants. However, in urine , several proteins, individually or in combination, were promising indicators of very early and preclinical kidney injury. The BMs with the highest sensitivity and specificity were collagen type XIII, hyaluronan binding protein 2 (HABP2), and complement C4 binding protein (C4BP).

Conclusion

We generated very strong candidate BMs by our approach of first examining preclinical AS in dogs and then validating these BMs in children at early stages of disease. These BMs might serve for screening purposes for AS before the onset of kidney damage and therefore allow preemptive therapy.

Current Understanding of Complement Proteins as Therapeutic Targets for the Treatment of Immunoglobulin A Nephropathy

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide and a frequent cause of kidney failure. Currently, the diagnosis necessitates a kidney biopsy, with routine immunofluorescence microscopy revealing IgA as the dominant or co-dominant immunoglobulin in the glomerular immuno-deposits, often with IgG and sometimes IgM or both. Complement protein C3 is observed in most cases. IgAN leads to kidney failure in 20-40% of patients within 20 years of diagnosis and reduces average life expectancy by about 10 years. There is increasing clinical, biochemical, and genetic evidence that the complement system plays a paramount role in the pathogenesis of IgAN. The presence of C3 in the kidney immuno-deposits differentiates the diagnosis of IgAN from subclinical glomerular mesangial IgA deposition. Markers of complement activation via the lectin and alternative pathways in kidney-biopsy specimens are associated with disease activity and are predictive of poor outcome. Levels of select complement proteins in the circulation have also been assessed in patients with IgAN and found to be of prognostic value. Ongoing genetic studies have identified at least 30 loci associated with IgAN. Genes within some of these loci encode complement-system regulating proteins that can interact with immune complexes. The growing appreciation for the central role of complement components in IgAN pathogenesis highlighted these pathways as potential treatment targets and sparked great interest in pharmacological agents targeting the complement cascade for the treatment of IgAN, as evidenced by the plethora of ongoing clinical trials.

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.

Comparative study on clinicopathological features and prognosis of IgA vasculitis nephritis and IgA nephropathy in children

BACKGROUND

IgA vasculitis nephritis (IgAVN) and IgA nephropathy (IgAN) share several clinical and pathological characteristics, though distinctions also exist. Their interrelation, however, remains undefined. This study investigates the clinicopathological divergences and prognostic disparities in pediatric patients with IgAVN and IgAN.

METHODS

Our study encompasses 809 pediatric patients with IgAVN and 236 with IgAN, all of whom underwent kidney biopsy. We utilized the Semiquantitative Classification (SQC) scoring system to juxtapose the pathologies of the two conditions, and performed a COX regression analysis to examine factors influencing their prognoses.

RESULTS

Both patient groups demonstrated a predominance of males. A seasonality was observed, with a higher incidence of IgAN in the summer, and IgAVN in the fall (P < 0.0001). Patients with IgAN exhibited more severe tubulointerstitial injury, higher chronicity index, and total biopsy scores compared to those with IgAVN (P < 0.0001). Mesangial deposition intensity of complement C3, and the rate of pure IgA deposition, were found to be greater in patients with IgAVN compared to those with IgAN (P < 0.0001). The intensity of IgA deposition was also significantly higher in IgAVN patients (P = 0.003). IgAVN demonstrated a superior prognosis, with a higher rate of kidney remission (P < 0.0001). COX regression analysis indicated that interstitial fibrosis, as identified in the SQC pathology system, was associated with the prognosis of both conditions. Furthermore, the findings suggest that IgA deposition levels (IgA +  + and IgA +  + +) could potentially influence the prognosis of IgAVN.

CONCLUSIONS

Compared to IgAVN, IgAN manifests more severely with regard to renal impairment, interstitial damage, and prognosis. The disparities in immune complex deposition levels and locations within the kidneys support the hypothesis of IgAVN and IgAN as distinct diseases. Interstitial fibrosis may serve as a key pathological indicator within the SQC system associated with kidney prognosis in children with IgAVN and IgAN. The degree of IgA deposition could also be linked with the prognosis of IgAVN.

A bibliometric analysis of complement in IgA nephropathy from 1991 to 2022

Introduction: IgA nephropathy is a common glomerular disease on a global scale, which has resulted in significant economic burdens. The complement system plays a vital role in enhancing the efficacy of antibodies and phagocytic cells in eliminating microbes and damaged cells, and promoting inflammation. Complement activation has been found to contribute to the progression of various renal diseases, including IgA nephropathy. Methods: In this study, a thorough analysis was conducted on publications related to complement in IgAN from 1991 to 2022, retrieved from the Web of Science Core Collection and Scopus database. The analysis focused on various aspects such as annual publications, country, institution, author, journal, keywords, and co-cited references, utilizing Citespace and Vosviewer. Results: A total of 819 publications were obtained, and while there were slight fluctuations in annual publications, an overall upward trend was observed. China, Japan and the United States were the leading countries in terms of publications, with China having the highest number of publications (201). Collaborative network analysis revealed that England, University of Alabama Birmingham, and Robert J Wyatt were the most influential country, institution, and author, respectively, in this field of research. Furthermore, the analysis of references and keywords indicated that complement activation contributes to IgAN, and immunosuppression in IgAN are a hot topic of research. Discussion: This study identifies current research hotspots and advanced tendencies in the study of complement in IgAN, providing scholars with crucial directions in this research area.

Glomerular Diseases Across Lifespan: Key Differences in Diagnostic and Therapeutic Approaches

Glomerular diseases are common causes of chronic kidney disease in childhood, adolescence, and adulthood. The epidemiology of glomerular diseases differs between different age groups, with minimal change disease being the leading cause of nephrotic syndrome in childhood, while membranous nephropathy and focal segmental glomerulosclerosis are more common in adulthood. IgA vasculitis is also more common in childhood. Moreover, there is a difference in disease severity with more children presenting with a relapsing form of nephrotic syndrome and a more acute presentation of antineutrophil cytoplasmic antibody-associated vasculitis and concomitant glomerulonephritis, as highlighted by the higher percentage of cellular crescents on kidney biopsy specimens in comparison with older patients. There is also a female preponderance in antineutrophil cytoplasmic antibody-associated vasculitis and more children present with tracheobroncholaryngeal disease. This article aims to summarize differences in the presentation of different glomerular diseases that are encountered commonly by pediatric and adult nephrologists and potential differences in the management.

Targeted Transcriptional Analysis of IgA Vasculitis, IgA Nephropathy, and IgA-Dominant Infection-Related Glomerulonephritis Reveals Both Distinct and Overlapping Immune Signatures

Key Points

Skin IL-9, calprotectin, and KIR gene expression may be predictive of subsequent kidney involvement in patients with IgAV. Histologically similar patients with IgAN, IgAV, and IgA-IRGN can be distinguished by their immune transcriptomes. Kidney biopsies from patients with IgA-IRGN are enriched for transcripts involved in granulocyte chemotaxis.

Background

IgA vasculitis (IgAV), IgA nephropathy (IgAN), and IgA-dominant infection-related glomerulonephritis (IgA-IRGN) have shared histopathologic features, but differences in clinical management and prognosis. The most serious IgAV organ involvement is in the kidneys (IgAV nephritis). In this study, we hypothesized that targeted immune transcript profiling could aid in (1 ) predicting the development of IgAV nephritis in patients with cutaneous IgAV and (2 ) differentiating IgAN, IgAV, and IgA-IRGN.

Methods

RNA was extracted from 24 formalin-fixed paraffin-embedded tissue specimens (16 kidney, 8 skin) from 21 patients with IgAV nephritis (n=7), IgAN (n=5), and IgA-IRGN (n=4), and IgAV skin biopsies from patients with (n=3) and without (n=5) IgAV nephritis. Differential gene expression and gene set enrichment analysis were performed on a total of 594 transcripts (Nanostring immunology panel) profiled using the nCounter system.

Results

Skin biopsies in patients with IgAV who develop kidney involvement exhibit reduced S100A8/S100A9 , IL9 , and killer cell immunoglobulin-like receptor expression. The kidney tissue immune transcriptomes of IgAN, IgAV, and IgA-IRGN are largely overlapping. IgA-IRGN kidney biopsies are, however, uniquely enriched for transcripts involved in granulocyte chemotaxis.

Conclusion

This study identifies immune transcript signatures that may predict IgAV nephritis in skin biopsies and distinguish IgA-IRGN from IgAN and IgAV in kidney biopsies.

Comparative proteomic analysis of glomerular proteins in IgA nephropathy and IgA vasculitis with nephritis

BACKGROUND

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAVN) are related glomerular diseases characterized by marked similarities in immunological and histological findings. We herein performed a comparative proteomic analysis of glomerular proteins in IgAN and IgAVN.

METHODS

We used renal biopsy specimens from 6 IgAN patients without nephrotic syndrome (NS) (IgAN-I subgroup), 6 IgAN patients with NS (IgAN-II subgroup), 6 IgAVN patients with 0-8.0% of glomeruli with crescent formation (IgAVN-I subgroup), 6 IgAVN patients with 21.2-44.8% of glomeruli with crescent formation (IgAVN-II subgroup), 9 IgAVN patients without NS (IgAVN-III subgroup), 3 IgAVN patients with NS (IgAN-IV subgroup), and 5 control cases. Proteins were extracted from laser microdissected glomeruli and analyzed using mass spectrometry. The relative abundance of proteins was compared between groups. An immunohistochemical validation study was also performed.

RESULTS

More than 850 proteins with high confidence were identified. A principal component analysis revealed a clear separation between IgAN and IgAVN patients and control cases. In further analyses, 546 proteins that were matched with ≥ 2 peptides were selected. The levels of immunoglobulins (IgA, IgG, and IgM), complements (C3, C4A, C5, and C9), complement factor H-related proteins (CFHR) 1 and 5, vitronectin, fibrinogen chains, and transforming growth factor-β inducible gene-h3 were higher (> 2.6 fold) in the IgAN and IgAVN subgroups than in the control group, whereas hornerin levels were lower (< 0.3 fold). Furthermore, C9 and CFHR1 levels were significantly higher in the IgAN group than in the IgAVN group. The abundance of some podocyte-associated proteins and glomerular basement membrane (GBM) proteins was significantly less in the IgAN-II subgroup than in the IgAN-I subgroup as well as in the IgAVN-IV subgroup than in the IgAVN-III subgroup. Among the IgAN and IgAVN subgroups, talin 1 was not detected in the IgAN-II subgroup. This result was supported by immunohistochemical findings.

CONCLUSIONS

The present results suggest shared molecular mechanisms for glomerular injury in IgAN and IgAVN, except for enhanced glomerular complement activation in IgAN. Differences in the protein abundance of podocyte-associated and GBM proteins between IgAN and IgAVN patients with and without NS may be associated with the severity of proteinuria.

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.

IgA vasculitis presenting as nephrotic syndrome following COVID-19 vaccination: a case report

BACKGROUND

Following the strong recommendation for coronavirus disease 2019 (COVID‑19) vaccination, many patients with medical comorbidities are being immunized. However, the safety of vaccination in patients with autoimmune diseases has not been well established. We report a new case of biopsy-proven IgA vasculitis with nephritis presenting as a nephrotic syndrome after mRNA COVID-19 vaccination in a patient with a history of leukocytoclastic vasculitis.

CASE PRESENTATION

A 76-year-old man with a history of cutaneous leukocytoclastic vasculitis presented with purpura in both lower limbs, followed by nephrotic syndrome after the second dose of BNT162b2 mRNA COVID-19 vaccination. Skin and renal biopsy revealed IgA vasculitis with nephritis. The patient's past medical history of leukocytoclastic vasculitis and features of chronicity in renal pathology suggest an acute exacerbation of preexisting IgA vasculitis after COVID-19 vaccination. After the steroid and renin-angiotensin system inhibitor use, purpura and acute kidney injury recovered within a month. Subnephrotic proteinuria with microscopic hematuria remained upon follow-up.

CONCLUSION

Physicians should keep in mind the potential (re)activation of IgA vasculitis following mRNA COVID-19 vaccines. It is important to closely monitor COVID-19 vaccinated patients, particularly those with autoimmune diseases.

Bibliometric analysis of IgA vasculitis nephritis in children from 2000 to 2022

Background

IgA vasculitis Nephritis (IgAVN) is a kidney-damaging disease that occurs during the course of IgA vasculitis (IgAV) and is the most serious complication of IgAV. However, there is a lack of reports of bibliometric analysis of IgAVN in children. The purpose of this study is to conduct a bibliometric analysis of IgAVN in children from 2000 to 2022, to explore the current status and cutting-edge trends in the field of IgAVN in children, and to establish new directions for subsequent research.

Methods

Screening the literature in the field of IgAVN in children in the Web of Science Core Collection (WoSCC) from 2000 to 2022. Visual analysis of their annual publications, countries, institutions, authors, journals, keywords, and references were using CiteSpace5.8.R3 and VOSviewer1.6.18.

Results

A total of 623 publications were included in the study, since the beginning of 2014, there has been an overall increasing trend in the number of articles issued. The most prolific country and institution were China and Zhejiang University. The most frequently cited author was Coppo R, with 331 citations, who has made great contributions to IgAVN. Mao Jianhua, Lee JS and Wyatt Robert J were the most prolific authors, all with 9 articles. Pediatric Nephrology was the most published and cited journal. The highest burst strength keyword is IgA vasculitis, and the highest burst strength reference is Davin JC, 2014.

Conclusion

The research hotspots and trends predicted by the analysis of this study provide a reference for in-depth research in this field with a view to promoting the development of IgAVN research in children.

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.

IgA vasculitis nephritis

PURPOSE OF REVIEW

The purpose of this update is to summarize current knowledge on the pathophysiology of immunglobulin A (IgA) vasculitis nephritis (IgAVN) as well as to critically review evidence for established therapeutic regimes and available biomarkers. An additional purpose is to raise the discussion what could be done to further improve our understanding of IgAVN, identify patients at risk for adverse outcome and increase the evidence for therapy recommendations.

RECENT FINDINGS

Clinical and experimental studies have established the concept of a multilevel pathogenesis. Toll-like-receptor activation, B cell proliferation, micro-RNAs and complement activation have been identified or confirmed as potential therapeutic targets which can modify the course of the disease. Currently, kidney injury molecule-1, monocyte chemotactic protein-1, N-acetyl-β-glucosaminidase, and angiotensinogen are the most promising urinary biomarkers for early diagnosis of renal involvement in IgA vasculitis.

SUMMARY

Close surveillance of all IgAV patients for renal involvement is recommended. Given the multilevel pathogenesis, early treatment of even mild cases should be initiated. Further therapeutic options should be considered in case first-line therapy (mostly corticosteroids) has no effect. The evidence supporting current therapeutic regimes is predominantly based on expert opinion. Prospective studies are needed and should involve substances inhibiting B cell proliferation and complement activation.

[Update on immunoglobulin A vasculitis]

Die Immunglobulin-A-Vaskulitis (IgAV) ist eine systemische Vaskulitis der kleinen Gefäße mit Ig(Immunglobulin)A-Immunkomplexbildung und einem breiten Spektrum klinischer Konstellationen. Typische Manifestationen sind Purpura, Arthralgien oder Arthritiden, Enteritis und Glomerulonephritis. Die IgAV ist die häufigste Vaskulitis im Kindesalter mit meist unkompliziertem und selbstlimitierendem Verlauf. Erwachsene erkranken deutlich seltener an einer IgAV, wobei die Verläufe insbesondere bei renaler oder gastrointestinaler Manifestation komplizierter sind. Verschiedene Trigger der IgAV, darunter Infektionen, wurden beschrieben, wobei eine gestörte Glykosylierung von IgA1 mit konsekutiver Freilegung von Bindungsstellen für Autoantikörper die pathophysiologische Voraussetzung für die Vaskulitis ist. Therapeutische Strategien mit Immunsuppressiva sind bisher mit geringer Evidenz unterlegt, berücksichtigen die Schwere der Organmanifestationen und orientieren sich an den Empfehlungen zur Behandlung anderer Vaskulitiden der kleinen Gefäße. Benigne Verläufe werden symptomatisch behandelt. Die langfristige Prognose der IgAV ist von der renalen Manifestation beeinflusst.

A case of pathologically confirmed streptococcal infection-related IgA vasculitis with associated glomerulonephritis and leukocytoclastic cutaneous vasculitis

We report the case of an 80 year-old woman who developed bilateral lower extremity purpura and renal impairment with proteinuria a few days after a transient fever (day 0). High levels of both anti-streptolysin-O antibody (ASO) and anti-streptokinase antibody (ASK), as well as low levels of coagulation factor XIII in serum were noted. Skin biopsy was performed and showed a leukocytoclastic vasculitis with deposition of IgA and C3 in the cutaneous small vessels, indicating IgA vasculitis in the skin. After initiation of oral prednisolone, the skin lesions showed significant improvement. However, renal function and proteinuria gradually worsened from day 12. Kidney biopsy was performed on day 29, which demonstrated a necrotizing and crescentic glomerulonephritis with mesangial deposition of IgA and C3. In addition, the deposition of galactose-deficient IgA1 (Gd-IgA1) was positive on glomeruli and cutaneous small vessels, indicating that the purpura and glomerulonephritis both shared the same Gd-IgA1-related pathogenesis. In addition, the association between the acute streptococcal infection and the IgA vasculitis was confirmed by the deposition of nephritis-associated plasmin receptor (NAPlr) in glomeruli. The patient was treated with steroid pulse and intravenous cyclophosphamide, in addition to the oral prednisolone treatment. Renal function and proteinuria gradually improved, but did not completely recover, as is typically seen with courses of IgA vasculitis in the elderly. In this case, the streptococcal infectionrelated IgA vasculitis was confirmed pathologically by the deposition of both NAPlr and Gd-IgA1 in glomeruli, as well as Gd-IgA1 in the cutaneous small vessels.

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.

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.

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.

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.

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.