IgA nephropathy Medical Services in China

IgA nephropathy (IgAN), also known as Berger’s disease, is a chronic autoimmune kidney disorder characterized by the deposition of immunoglobulin A (IgA) immune complexes in the glomerular mesangium. This triggers localized inflammation, mesangial cell proliferation, and extracellular matrix expansion—ultimately leading to progressive glomerulosclerosis, tubulointerstitial fibrosis, and declining renal function. Pathogenesis involves a multifactorial interplay: aberrant glycosylation of IgA1 (particularly deficient galactosylation in the hinge region), generation of autoantibodies against these neoepitopes, formation of circulating IgA1-containing immune complexes, impaired hepatic clearance, and subsequent mesangial deposition. Complement activation—especially via the lectin and alternative pathways—amplifies injury, while genetic susceptibility (e.g., variants in CFHR1, DEFA, HLA-DQB1) and environmental triggers (mucosal infections, gut dysbiosis, smoking) modulate disease onset and progression. Epidemiologically, IgAN is the most common primary glomerulonephritis worldwide, with highest prevalence in East Asia (incidence ~2.5–4.5 per 100,000/year), intermediate rates in Europe (~1.0–2.0), and lower incidence in Africa and Latin America. It typically presents in adolescence or early adulthood (peak onset 16–35 years), with a male-to-female ratio of ~2:1. Key risk factors include familial clustering (10–15% of cases), Asian or Caucasian ethnicity, recurrent upper respiratory or gastrointestinal infections, celiac disease, HIV, and liver cirrhosis. Clinical manifestations range from asymptomatic microscopic hematuria and mild proteinuria to episodic macroscopic hematuria (often post-infectious), hypertension, nephrotic-range proteinuria (>3.5 g/day), and progressive chronic kidney disease (CKD). Approximately 20–40% of untreated patients progress to end-stage kidney disease (ESKD) within 20 years. Quality of life is significantly impacted—not only by physical symptoms (fatigue, edema, nocturia) but also by psychological burden (anxiety about progression, treatment adherence challenges), dietary restrictions (low-sodium, low-protein diets), medication side effects (e.g., corticosteroid-induced weight gain, mood changes), and socioeconomic strain from long-term monitoring, dialysis, or transplant preparation. Early diagnosis via renal biopsy remains essential for risk stratification, as clinical presentation alone cannot reliably predict prognosis. Emerging biomarkers—including serum galactose-deficient IgA1, anti-glycan antibodies, and urinary CD89 complexes—are under validation for non-invasive monitoring. With growing understanding of pathogenic mechanisms, targeted therapies (e.g., Nefecon, budesonide targeting gut-associated lymphoid tissue; anti-APRIL agents like atacicept and telitacicept) are reshaping management paradigms beyond conventional supportive care.

IgA nephropathy (IgAN), also known as Berger’s disease, is the most common primary glomerulonephritis worldwide. It is characterized by the deposition of immunoglobulin A1 (IgA1)-containing immune complexes in the mesangium of the glomeruli, leading to inflammation, mesangial cell proliferation, matrix expansion, and progressive renal injury. The precise etiology remains incompletely understood, but current evidence supports a multifactorial pathogenesis involving aberrant mucosal immunity, defective IgA1 glycosylation, autoantibody formation, and genetic susceptibility.

The central pathogenic mechanism involves the production of galactose-deficient IgA1 (Gd-IgA1). In healthy individuals, IgA1 hinge region O-glycans are normally capped with galactose; in IgAN patients, this glycosylation is impaired—specifically, there is reduced activity of core 1 β1,3-galactosyltransferase (C1GALT1) and its chaperone Cosmc. This results in exposed N-acetylgalactosamine (GalNAc) residues on circulating IgA1. Gd-IgA1 acts as an autoantigen, prompting the production of IgG (and occasionally IgA) autoantibodies that recognize the aberrantly glycosylated epitopes. These immune complexes—comprising Gd-IgA1 and anti-Gd-IgA1 antibodies—are poorly cleared, deposit in the glomerular mesangium, activate the lectin and alternative complement pathways, and trigger local inflammation, cytokine release (e.g., IL-6, TNF-α), and mesangial cell activation.

Triggers often involve mucosal immune challenges. Upper respiratory tract infections (e.g., pharyngitis, sinusitis), gastrointestinal infections (e.g., Campylobacter jejuni, Shigella), and less commonly, viral illnesses (e.g., influenza, Epstein-Barr virus) frequently precede hematuria flares or disease onset. These events stimulate mucosal B-cell activation and IgA1 synthesis, particularly at gut- and respiratory-associated lymphoid tissue (GALT and BALT), thereby amplifying Gd-IgA1 production and immune complex formation. Exercise-induced hematuria and heavy alcohol consumption may also provoke acute macroscopic hematuria episodes in susceptible individuals.

Established risk factors for disease progression include persistent proteinuria (>0.5–1.0 g/day), hypertension (especially uncontrolled), male sex, older age at diagnosis (>40 years), impaired baseline estimated glomerular filtration rate (eGFR <60 mL/min/1.73 m²), and histopathological features such as crescent formation, interstitial fibrosis, tubular atrophy, and global glomerulosclerosis on kidney biopsy. Smoking is an independent modifiable risk factor associated with faster eGFR decline and increased risk of end-stage kidney disease (ESKD).

Genetic factors play a substantial role. Genome-wide association studies (GWAS) have identified multiple susceptibility loci, most notably within the major histocompatibility complex (MHC) region on chromosome 6p21, implicating HLA-DQB1, HLA-DRB1, and HLA-B alleles. Non-MHC loci include genes involved in IgA biology (e.g., CFHR1–CFHR3 deletion confers protection), complement regulation (e.g., CD46, C3), and mucosal immunity (e.g., TNFSF13, DEFA). Familial clustering occurs in ~5–10% of cases, and first-degree relatives of IgAN patients show elevated serum Gd-IgA1 levels even without clinical disease—suggesting inherited dysregulation of IgA1 glycosylation and immune complex handling.

Environmental influences interact with genetic background. Endemic prevalence is highest in East Asia (Japan, Korea, China), intermediate in Southern Europe, and lowest in North America and Africa—pointing to gene–environment interactions. Dietary factors—including high sodium intake, which exacerbates hypertension and proteinuria, and possibly gluten exposure in genetically predisposed individuals—may modulate immune responses. Air pollution (e.g., PM2.5) has been epidemiologically linked to increased IgAN incidence and flare frequency, potentially via systemic inflammation and oxidative stress. Chronic mucosal antigenic stimulation—such as from recurrent tonsillitis, chronic periodontitis, or untreated celiac disease—may perpetuate Gd-IgA1 overproduction. Notably, while Helicobacter pylori infection is not causative, eradication may reduce Gd-IgA1 levels in some cohorts, suggesting a contributory role in immune dysregulation.

In summary, IgA nephropathy arises from a convergence of intrinsic (genetically driven IgA1 glycosylation defects, complement dysregulation) and extrinsic (mucosal infections, environmental toxins, lifestyle exposures) factors. Understanding these interrelationships is critical for risk stratification, targeted monitoring, and emerging therapies aimed at Gd-IgA1 production, immune complex clearance, or downstream inflammatory effectors.

IgA nephropathy (IgAN), also known as Berger’s disease, is the most common primary glomerulonephritis worldwide and a leading cause of end-stage kidney disease (ESKD) in young adults. It is characterized by dominant or codominant mesangial deposition of immunoglobulin A1 (IgA1) with associated complement activation, triggering chronic inflammation, mesangial proliferation, and progressive glomerulosclerosis. Clinical presentation is highly heterogeneous—ranging from asymptomatic microscopic hematuria to rapidly progressive glomerulonephritis—and often correlates poorly with histopathologic severity. Early symptoms are frequently subtle and nonspecific, contributing to delayed diagnosis. The earliest and most common manifestation is episodic, painless, macroscopic hematuria, typically occurring within 1–3 days following an upper respiratory tract infection (e.g., pharyngitis, sinusitis) or, less commonly, gastrointestinal illness. This synpharyngeal hematuria reflects mucosal immune dysregulation and aberrant IgA1 glycosylation, resulting in immune complex formation and glomerular deposition. Microscopic hematuria—detected incidentally on urinalysis—is even more prevalent, present in up to 90% of patients at diagnosis, and may persist chronically without overt episodes. Mild, non-nephrotic range proteinuria (<1 g/day) is also common early on; however, isolated proteinuria without hematuria is rare and should prompt reconsideration of alternative diagnoses. Hypertension is uncommon in early-stage IgAN but may emerge as renal function declines.

Typical symptoms reflect progressive glomerular injury and include persistent microscopic hematuria with dysmorphic red blood cells and red blood cell casts, indicative of glomerular origin. Proteinuria often increases over time, with approximately 30–40% of patients developing nephrotic-range proteinuria (>3.5 g/day), accompanied by hypoalbuminemia, edema (especially periorbital and lower extremity), and hyperlipidemia. Sustained hypertension becomes increasingly prevalent as estimated glomerular filtration rate (eGFR) falls below 60 mL/min/1.73 m², reflecting both renal parenchymal damage and activation of the renin-angiotensin-aldosterone system (RAAS). Patients may report fatigue, reduced exercise tolerance, and mild flank discomfort—though true renal colic is absent, distinguishing IgAN from obstructive uropathy or nephrolithiasis.

Accompanying symptoms often reflect systemic immune dysregulation or comorbid conditions. Recurrent mucosal infections—including chronic sinusitis, tonsillitis, and celiac disease—are observed at higher frequency than in the general population, supporting the hypothesis of mucosal IgA1 overproduction. Some patients report arthralgias or low-grade fevers during hematuric flares, though systemic inflammatory signs (e.g., rash, lymphadenopathy, weight loss) are atypical and should raise suspicion for vasculitis or lupus nephritis. Gastrointestinal symptoms such as abdominal pain or diarrhea may occur in association with Henoch-Schönlein purpura (HSP), the systemic counterpart of IgAN; however, in isolated IgAN, extrarenal manifestations are absent. Notably, patients rarely present with acute kidney injury (AKI) unless complicated by crescentic transformation, severe volume depletion, or concurrent nephrotoxic exposure.

Complications arise from chronic glomerular injury and progressive fibrosis. The most consequential is chronic kidney disease (CKD), with ~20–40% of patients progressing to ESKD over 20 years. Risk factors for progression include persistent proteinuria >1 g/day, hypertension uncontrolled to <130/80 mmHg, impaired baseline eGFR, male sex, older age at onset, and specific histopathologic features (e.g., crescents >25%, interstitial fibrosis/tubular atrophy >25%, global glomerulosclerosis). Cardiovascular complications—including left ventricular hypertrophy, coronary artery disease, and stroke—are markedly increased due to CKD-associated uremic cardiomyopathy, accelerated atherosclerosis, and RAAS overactivity. Hyperkalemia, metabolic acidosis, and anemia of chronic disease develop as eGFR declines. Rarely, patients develop nephrotic syndrome–associated thromboembolic events (e.g., renal vein thrombosis, pulmonary embolism) due to urinary antithrombin III loss and hypercoagulability. In advanced disease, secondary hyperparathyroidism, renal osteodystrophy, and uremic neuropathy may manifest.

Diagnosis requires integration of clinical, laboratory, and histopathologic data. Urinalysis consistently reveals hematuria (microscopic or macroscopic) with dysmorphic RBCs and/or RBC casts; urine protein-to-creatinine ratio (UPCR) quantifies proteinuria. Serum creatinine and eGFR assess functional impairment; serum albumin, lipid panel, and complement levels (C3, C4) are typically normal—low C3 suggests alternative complement pathway activation (e.g., C3 glomerulopathy) or post-infectious GN. Serologic testing excludes mimics: negative ANA, anti-dsDNA, ANCA, anti-GBM antibodies, and hepatitis serologies are expected. Renal biopsy remains the gold standard: light microscopy shows mesangial hypercellularity and matrix expansion; immunofluorescence demonstrates dominant or codominant mesangial IgA deposits (with IgG and/or IgM in ~30%), often with C3; electron microscopy reveals electron-dense mesangial deposits. The Oxford MEST-C classification (mesangial hypercellularity, endocapillary hypercellularity, segmental glomerulosclerosis, tubular atrophy/interstitial fibrosis, crescents) provides prognostic stratification.

Differential diagnosis is critical. Post-infectious glomerulonephritis (PIGN) presents similarly with post-streptococcal hematuria and proteinuria but features subepithelial humps on EM, low serum C3, and resolves spontaneously. Lupus nephritis may mimic IgAN but shows multi-class immune deposits (IgG dominant), positive serologies (ANA, anti-dsDNA), and extrarenal manifestations. ANCA-associated vasculitis (e.g., granulomatosis with polyangiitis) causes pauci-immune crescentic GN, with necrotizing lesions, minimal immune deposits, and positive ANCA. Thin basement membrane nephropathy presents with lifelong microscopic hematuria but lacks proteinuria, hypertension, or progression; biopsy shows diffuse GBM thinning without immune deposits. Alport syndrome features hematuria plus sensorineural hearing loss and ocular abnormalities, with GBM lamellation on EM. Finally, membranoproliferative GN (MPGN) exhibits C3-dominant deposits, low C3, and often systemic complement dysregulation. Accurate distinction relies on comprehensive serologic evaluation, careful histopathologic interpretation, and clinical context—notably, the absence of systemic features, normal complement, and isolated IgA-dominant deposits strongly support IgAN.

IgA nephropathy (IgAN), or Berger’s disease, is the most common primary glomerulonephritis worldwide, characterized by dominant or codominant IgA1-containing immune deposits in the mesangium. Its clinical course is highly variable—ranging from asymptomatic microscopic hematuria and mild proteinuria to progressive chronic kidney disease (CKD) and end-stage kidney disease (ESKD) over decades. Management in nephrology departments emphasizes risk stratification, individualized therapy, and long-term renal protection. Treatment strategies are broadly categorized into conservative (nonpharmacologic) measures, pharmacologic interventions, and—rarely—surgical approaches. Importantly, no single therapy is universally effective; decisions must integrate histopathologic findings (e.g., Oxford MEST-C score), estimated glomerular filtration rate (eGFR), proteinuria level (>0.5–1.0 g/day signals higher risk), hypertension control, and comorbidities.

Conservative treatment forms the cornerstone of IgAN management and should be initiated at diagnosis, regardless of disease activity. This includes strict blood pressure control targeting <120/80 mmHg (per KDIGO 2021 guidelines), achieved preferentially with renin-angiotensin-aldosterone system inhibitors (RAASi)—angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARBs). These agents reduce intraglomerular pressure, attenuate podocyte injury, and exert antiproteinuric effects independent of BP lowering. Dietary sodium restriction (<2 g/day) potentiates RAASi efficacy and mitigates fluid retention. A low-protein diet (0.8 g/kg/day) may slow CKD progression in patients with eGFR <60 mL/min/1.73m², though evidence remains modest and requires nutritional supervision to prevent sarcopenia. Smoking cessation, weight optimization (BMI 18.5–24.9 kg/m²), and avoidance of nephrotoxic agents—including NSAIDs and iodinated contrast—constitute essential lifestyle modifications. Regular monitoring of serum creatinine, urine albumin-to-creatinine ratio (UACR), and eGFR every 3–6 months enables timely intervention escalation.

Pharmacologic therapy is indicated for patients with persistent proteinuria ≥1.0 g/day despite 3–6 months of optimized conservative care and stable eGFR ≥30 mL/min/1.73m². First-line immunosuppression remains controversial; corticosteroids (e.g., 6-month oral prednisone taper) demonstrated benefit in the STOP-IgAN and TESTING trials but carry significant risks—particularly diabetes, osteoporosis, and infection. The TESTING trial confirmed reduced risk of CKD progression with steroid therapy but mandated gastroprotection and stringent infection surveillance. More recently, targeted-release budesonide (Nefecon®), delivered to gut-associated lymphoid tissue to modulate aberrant IgA1 production, received FDA and EMA approval for high-risk IgAN (proteinuria ≥1 g/day, eGFR 35–90 mL/min/1.73m²). In the NefIgArd trial, it significantly reduced proteinuria and slowed eGFR decline over 2 years. Other emerging agents include SGLT2 inhibitors (e.g., dapagliflozin), which—regardless of diabetes status—reduce intraglomerular pressure, tubulointerstitial hypoxia, and inflammation; the DAPA-CKD trial included IgAN subgroups showing consistent renal and cardiovascular benefits. Endothelin receptor antagonists (e.g., atrasentan) and complement inhibitors (e.g., iptacopan, narsoplimab) are under active phase III investigation. Anticoagulation and antiplatelet therapy are not recommended outside specific thrombotic microangiopathy contexts due to lack of proven benefit and bleeding risk.

Surgical treatment has no established role in IgAN pathophysiology. Nephrectomy is contraindicated except in rare cases of unilateral, massive, life-threatening hemorrhage unresponsive to embolization—a scenario virtually nonexistent in routine practice. Kidney transplantation remains the definitive therapy for ESKD secondary to IgAN; however, disease recurrence in the allograft occurs in ~40–60% of recipients, typically within 5 years. Recurrence rarely causes graft loss unless accompanied by aggressive histologic features (e.g., crescents, fibrosis). Pre-transplant evaluation includes assessment of donor-specific antibodies and careful counseling regarding recurrence risk—not surgical intervention per se.

China offers distinct advantages in IgAN management, rooted in integrated traditional Chinese medicine (TCM) and modern nephrology. Over 30 Class I hospitals—including Peking University First Hospital and Shanghai Renji Hospital—operate specialized IgAN clinics with multidisciplinary teams (nephrologists, pathologists, TCM physicians, dietitians). China pioneered large-scale prospective registries (e.g., the China IgAN Registry), enabling real-world evidence generation on treatment patterns and outcomes. TCM adjuncts—such as Tripterygium wilfordii Hook F (TwHF) and Huangkui capsule—have demonstrated antiproteinuric and anti-inflammatory effects in randomized trials, though standardization and quality control remain critical. Moreover, China’s national health insurance covers key therapies—including RAASi, SGLT2 inhibitors, and Nefecon—reducing financial toxicity. Rapid diagnostic infrastructure (e.g., digital pathology platforms for Oxford scoring) and centralized biopsy review networks improve diagnostic accuracy. Clinical trial participation is robust: Chinese sites contributed >25% of global enrollment in the NefIgArd trial, accelerating access to novel therapeutics.

Recovery and long-term prognosis hinge on sustained adherence and proactive self-management. Patients should maintain daily home BP logs, perform monthly UACR spot checks if feasible, and avoid herbal remedies with unknown nephrotoxic potential (e.g., aristolochic acid-containing herbs). Vaccination against influenza, pneumococcus, and hepatitis B is strongly advised, especially before immunosuppression. Annual ophthalmologic screening detects hypertensive or diabetic retinopathy early. Psychological support is integral—chronic kidney disease correlates with elevated depression and anxiety prevalence; structured counseling and peer support groups improve treatment concordance. Women of childbearing age require preconception counseling: ACEi/ARBs and immunosuppressants are teratogenic; pregnancy is generally safe with proteinuria <1 g/day and stable eGFR >70 mL/min/1.73m² but mandates close maternal-fetal surveillance. Finally, transition planning for adolescents with IgAN ensures continuity into adult nephrology care, minimizing gaps during critical developmental windows. With comprehensive, evidence-informed, and patient-centered care, many individuals with IgAN maintain stable kidney function for decades—underscoring that early recognition, rigorous conservative foundation, judicious pharmacotherapy, and holistic support collectively define optimal outcomes.