Iga Nephritis

Overview

• Definition: IgA nephropathy (IgAN), also known as Berger's disease, is the most common primary glomerulonephritis worldwide. It is characterized by the deposition of immunoglobulin A (IgA) in the mesangium of the glomeruli, leading to inflammation and progressive renal damage.

• Epidemiology:

  • IgAN affects approximately 25 individuals per million population annually in Western countries and is even more prevalent in Asia, particularly East Asia (e.g., China, Japan, Korea), where it accounts for 30-40% of primary glomerulonephritis cases.
  • Typically presents in the second or third decade of life (peak incidence 20-30 years), but can occur at any age.
  • Male-to-female ratio is about 2:1.
  • Geographic variations may be partly due to differences in diagnostic biopsy practices.

• Classification:

  • Primary IgAN: Not associated with other systemic diseases.
  • Secondary IgAN: Associated with other conditions such as:
    • Gastrointestinal diseases: Celiac disease, inflammatory bowel disease, liver cirrhosis (especially alcoholic liver disease).
    • Autoimmune diseases: Systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis.
    • Infections: HIV, chronic hepatitis B/C.
    • Malignancies: Certain lymphomas, carcinomas.
  • Oxford Classification (MEST-C Score): A widely used histopathological classification system based on light microscopy findings, which correlates with prognosis:
    • Mesangial hypercellularity (M0: <50% glomeruli, M1: ≥50% glomeruli)
    • Endocapillary hypercellularity (E0: Absent, E1: Present)
    • Segmental glomerulosclerosis (S0: Absent, S1: Present)
    • Tubular atrophy/interstitial fibrosis (T0: ≤25%, T1: 26-50%, T2: >50%)
    • Crescents (C0: Absent, C1: <25%, C2: 25-50%, C3: >50%)

Pathophysiology

• Mechanism: The "multi-hit" hypothesis is widely accepted, involving four key steps:

  1. First Hit: Production of aberrantly glycosylated IgA1 (Galactose-deficient IgA1, Gd-IgA1) by bone marrow and mucosal B cells. This IgA1 lacks galactose residues in its hinge region O-glycans.
  2. Second Hit: Formation of autoantibodies (IgG or IgA) against Gd-IgA1.
  3. Third Hit: Formation of immune complexes (Gd-IgA1 and anti-Gd-IgA1 antibodies) in the circulation.
  4. Fourth Hit: Deposition of these immune complexes in the glomerular mesangium, stimulating proliferation of mesangial cells and release of pro-inflammatory cytokines, chemokines, and growth factors (e.g., TGF-β). This leads to mesangial cell proliferation, extracellular matrix expansion, and ultimately glomerular injury, potentially involving complement activation (lectin and alternative pathways).

• Risk Factors:

  • Genetic predisposition (e.g., HLA-DRB1*0401, specific gene variants involved in immune response and glycosylation).
  • Family history of IgAN.
  • Recurrent mucosal infections (e.g., upper respiratory tract infections, gastroenteritis) often precede episodes of gross hematuria.

• Protective Factors: None definitively identified. General healthy lifestyle might mitigate disease progression but does not prevent onset.

Clinical Presentation

Signs and Symptoms

• Cardinal Features:

  • Gross Hematuria: Often macroscopic, typically occurring within 1-3 days after a mucosal infection (e.g., pharyngitis, sinusitis, gastroenteritis) ("synpharyngitic" hematuria). This differentiates it from post-streptococcal glomerulonephritis, where gross hematuria usually occurs 1-3 weeks after infection. Episodes are usually self-limiting but recur.
  • Microscopic Hematuria: Persistent, often incidentally found on routine urinalysis.
  • Proteinuria: Variable, ranging from mild (<1 g/day) to nephrotic range (>3.5 g/day).
  • Hypertension: Present in a significant proportion of patients, particularly those with more advanced disease.

• Early Signs:

  • Recurrent episodes of gross hematuria, especially post-infectious.
  • Persistent microscopic hematuria.
  • Mild proteinuria.
  • Often asymptomatic initially, with discovery through routine urine testing.

• Advanced Signs:

  • Progressive chronic kidney disease (CKD) with rising serum creatinine and declining GFR.
  • Worsening hypertension.
  • Edema (due to nephrotic range proteinuria or renal failure).
  • Symptoms of uremia (fatigue, nausea, pruritus) in end-stage renal disease (ESRD).

• Atypical Presentations:

  • Rapidly Progressive Glomerulonephritis (RPGN): Severe crescentic IgAN, leading to swift decline in renal function.
  • Nephrotic Syndrome: Though typically associated with other glomerulonephritides, 5-10% of IgAN patients can present primarily with nephrotic syndrome.

Physical Examination

• Inspection:

  • May be normal in early disease.
  • Edema (periorbital, ankle, sacral) in cases with nephrotic syndrome or significant renal impairment.
  • Pallor (anemia of CKD).
  • Rarely, signs of associated systemic disease (e.g., skin rash in Henoch-Schönlein purpura, which is a systemic vasculitis with IgA deposition affecting skin, joints, GI tract, and kidneys).

• Palpation: Normal. Kidneys not typically palpable unless massively hydronephrotic.

• Special Tests: No specific physical examination tests for IgAN. Focus is on assessing hydration status, blood pressure, and signs of complications.

Diagnostic Approach

History Taking

• Key Questions:

  • Detailed history of hematuria: onset, timing (relation to infections), color (cola-colored vs. bright red), duration, recurrence.
  • History of recent infections (upper respiratory, gastrointestinal).
  • Presence of foamy urine (suggestive of proteinuria).
  • Symptoms of edema, fatigue, nausea, shortness of breath.
  • Family history of kidney disease or IgAN.
  • Medication history (especially NSAIDs, nephrotoxic drugs).
  • History of systemic diseases (e.g., liver disease, autoimmune conditions, celiac disease).

• Red Flags:

  • Rapid decline in urine output or sudden rise in serum creatinine (suggests RPGN).
  • Symptoms of significant volume overload (pulmonary edema, severe edema).
  • Blood pressure crisis.

Laboratory Tests

• First-Line:

  • Urinalysis with Microscopy:
    • Microscopic or gross hematuria (dysmorphic red blood cells, RBC casts are highly suggestive of glomerular origin).
    • Proteinuria (dipstick positive, quantification with urine protein-to-creatinine ratio (UPCR) or 24-hour urine collection).
  • Serum Creatinine and eGFR: To assess renal function.
  • Blood Pressure Measurement: Essential for all patients.
  • Complete Blood Count (CBC): To check for anemia.
  • Electrolytes (Na, K, HCO3): To evaluate kidney function and acid-base status.

• Confirmatory:

  • Kidney Biopsy: The gold standard for diagnosis. Essential to confirm IgAN and assess severity, prognosis, and guide treatment.
    • Light Microscopy: Mesangial proliferation, matrix expansion. May show focal segmental glomerulosclerosis, endocapillary proliferation, crescent formation, or tubular atrophy/interstitial fibrosis.
    • Immunofluorescence (IF): Dominant or co-dominant mesangial IgA deposition (usually IgA1 subtype), often with C3 and sometimes IgG or IgM. C1q is typically negative, differentiating it from lupus nephritis.
    • Electron Microscopy (EM): Electron-dense deposits in the mesangium.

• Monitoring:

  • Serial measurement of UPCR or 24-hour urine protein: To monitor proteinuria, a key marker of disease activity and progression.
  • Serum creatinine and eGFR: To track renal function.
  • Blood pressure: Regularly monitored and managed.
  • Serial urinalysis: To track hematuria.

Imaging

• Recommended:

  • Renal Ultrasound: To assess kidney size, rule out obstruction, identify chronic kidney disease features (e.g., increased echogenicity, reduced cortical thickness). Not diagnostic for IgAN itself but essential to rule out other causes of hematuria and assess CKD chronicity.

• Advanced:

  • No advanced imaging specifically diagnostic for IgAN. In select cases, MRA/CTA might be considered for evaluation of renal artery stenosis if severe hypertension is refractory or GFR decline is disproportionate to proteinuria, but this is not typical for IgAN diagnosis.

Management

Acute Management

• Immediate:

  • Severe Gross Hematuria: If causing significant blood loss or clot formation leading to obstruction, may require hydration, blood transfusion, or urological consultation.
  • Hypertensive Crisis: Immediate BP control with intravenous antihypertensives (e.g., nicardipine, labetalol) to prevent end-organ damage.

• Stabilization:

  • Volume Overload: Diuretics (loop diuretics like furosemide) if symptoms of pulmonary edema or severe peripheral edema.
  • Electrolyte Abnormalities: Correction of hyperkalemia, metabolic acidosis.
  • Acute Kidney Injury (AKI): Address reversible causes, consider urgent dialysis if severe AKI with life-threatening complications (e.g., refractory hyperkalemia, severe acidosis, pulmonary edema).

• Emergency:

  • Rapidly Progressive Glomerulonephritis (RPGN) with crescents on biopsy: High-dose corticosteroids (e.g., methylprednisolone 0.5-1 g IV daily for 3 days) often followed by oral prednisone, sometimes combined with cyclophosphamide (e.g., 0.5-1 g/m² IV monthly for 3-6 months), especially if >50% crescents. Plasma exchange is controversial but may be considered in severe, rapidly progressive cases.

Chronic Management

• Pharmacological:

  • Renin-Angiotensin System (RAS) Blockade: Cornerstone of therapy for proteinuria and hypertension.
    • ACE Inhibitors (ACEi) or Angiotensin Receptor Blockers (ARBs): Indicated for all patients with proteinuria >0.5-1 g/day, and for hypertension. Target blood pressure <120/80 mmHg (or specific targets per current guidelines, e.g., <130/80 mmHg). Titrate to maximum tolerated dose or until proteinuria is optimally reduced. Examples: Lisinopril 10-40 mg PO daily, Valsartan 80-320 mg PO daily.
  • Corticosteroids:
    • Systemic corticosteroids: Considered for patients with persistent proteinuria (>0.75-1 g/day despite RAS blockade) and declining eGFR (e.g., eGFR 30-50 mL/min/1.73m²), particularly with active inflammation on biopsy. E.g., Prednisone 0.5-1 mg/kg/day (max 60 mg/day) for 2-3 months, tapered over 6-9 months, or a reduced-dose regimen like 0.4 mg/kg/day. Shared decision-making is crucial due to side effects.
    • Budesonide (targeted-release formulation, e.g., Nefecon): Specifically targets Peyer's patches in the ileum, reducing IgA1 production. Approved for IgAN patients at risk of progression. Dose: 16 mg PO once daily for 9 months.
  • SGLT2 Inhibitors: (e.g., Dapagliflozin 10 mg PO daily, Empagliflozin 10 mg PO daily)
    • Recommended for patients with CKD and albuminuria (urine albumin-to-creatinine ratio (UACR) ≥200 mg/g) to reduce progression of kidney disease and cardiovascular events, regardless of diabetes status. This applies to IgAN.
  • Immunosuppressants (other than corticosteroids):
    • Cyclophosphamide: Primarily for RPGN.
    • Mycophenolate Mofetil (MMF): (e.g., 1-2 g PO daily in divided doses)
      • May be considered in patients intolerant or unresponsive to corticosteroids, or as an alternative in specific populations (e.g., East Asians, where some studies show benefit). Evidence for first-line use is not as strong as for corticosteroids, especially in non-Asian populations.
    • Calcineurin Inhibitors (CNIs): (e.g., Cyclosporine, Tacrolimus)
      • Less commonly used due to nephrotoxicity, but may be an option for steroid-resistant nephrotic syndrome secondary to IgAN.
  • Omega-3 Fatty Acids (Fish Oil): (e.g., 2-4 g/day)
    • Historically used, but evidence for significant renal protective effect is inconsistent, particularly in the current era of RAS blockade. May be considered as an adjunct, especially in patients with high dietary intake of omega-3s.

• Non-pharmacological:

  • Dietary Sodium Restriction: <2 g/day for blood pressure and edema control.
  • Dietary Protein Restriction: Moderate restriction (0.8 g/kg/day) for patients with advanced CKD to potentially slow progression, but clinical benefits are modest.
  • Maintenance of Ideal Body Weight: Obesity exacerbates CKD progression.
  • Smoking Cessation: Crucial for overall renal and cardiovascular health.
  • Regular Exercise: As tolerated.

• Monitoring:

  • Regular BP monitoring: In clinic and at home.
  • Serum creatinine and eGFR: Every 3-6 months, or more frequently if rapidly declining or during dose titration of medications.
  • Urinalysis with UPCR: Every 3-6 months to assess proteinuria and hematuria.
  • Electrolytes: To monitor side effects of RAS blockers and SGLT2 inhibitors.
  • Lipid panel: Hyperlipidemia is common, especially with proteinuria, and should be managed per guidelines (statins).
  • Bone mineral density: For patients on long-term corticosteroids.

Treatment Algorithms

• First-Line:

  1. Supportive Care: BP control (<130/80 mmHg), RAS blockade (ACEi/ARB) for proteinuria (>0.5 g/day or >500 mg/g UPCR), dietary sodium restriction.
  2. SGLT2 Inhibitor: For patients with CKD and albuminuria (UACR >200 mg/g).

• Second-Line:

  1. Systemic Corticosteroids: For patients with persistent proteinuria (>0.75-1 g/day despite 3-6 months of optimized supportive care including RAS blockade and SGLT2i), and an eGFR >30 mL/min/1.73m², without significant C-scores on Oxford biopsy.
  2. Targeted-release budesonide (Nefecon): Alternative or addition to systemic corticosteroids for similar indications, particularly when avoiding systemic steroid side effects.

• Refractory Cases:

  1. Repeat Kidney Biopsy: To reassess disease activity and chronicity if response is poor or eGFR declines rapidly.
  2. Immunosuppressants: For severe, progressive cases not responding to steroids.
     • MMF: Consider if corticosteroids are contraindicated or poorly tolerated, or if there's evidence for benefit (e.g., in East Asian populations).
     • Cyclophosphamide: Primarily for crescentic IgAN or RPGN.
  3. Rituximab: Limited evidence, mostly in small series and case reports for steroid-resistant severe cases or RPGN. Not routinely recommended.
  4. Clinical Trials: Enrollment in clinical trials for novel IgAN therapies (e.g., complement inhibitors, B-cell targeting agents) may be an option.
  5. ESRD Management: Ultimately, renal replacement therapy (dialysis or kidney transplant) for progression to ESRD. IgAN can recur in kidney transplant allografts (up to 50% incidence histologically by 10 years, symptomatic recurrence in 10-30%).

Complications

• Common:

  • Hypertension: Affects up to 60% of patients.
  • Proteinuria: Can lead to edema and increase risk of CKD progression.
  • Chronic Kidney Disease (CKD): Progressive loss of renal function. Approximately 20-40% of patients progress to ESRD within 10-20 years.
  • Anemia: Due to CKD.

• Serious:

  • End-Stage Renal Disease (ESRD): Requiring dialysis or kidney transplantation.
  • Cardiovascular Disease: Increased risk due to hypertension, dyslipidemia, and CKD.
  • Acute Kidney Injury (AKI): Can be due to severe gross hematuria (obstructive nephropathy from clots), superimposed acute tubular necrosis, or rapidly progressive glomerulonephritis.
  • Infections: Increased risk with immunosuppressive therapy.

• Long-term:

  • Recurrence of IgAN in transplanted kidney.
  • Increased morbidity and mortality from cardiovascular events.

Prognosis

• Factors:

  • Good Prognostic Factors:
    • Preserved GFR at presentation.
    • Mild or intermittent microscopic hematuria without proteinuria.
    • Absence of hypertension.
    • Lack of significant mesangial hypercellularity, segmental sclerosis, interstitial fibrosis, or crescents on biopsy (low Oxford MEST-C score).
  • Poor Prognostic Factors:
    • Persistent proteinuria >1 g/day.
    • Elevated serum creatinine or reduced eGFR at presentation.
    • Uncontrolled hypertension.
    • Older age at onset.
    • Presence of endocapillary hypercellularity, segmental sclerosis, tubular atrophy/interstitial fibrosis, or crescents on biopsy (high Oxford MEST-C score, especially T1/T2 and C1/C2/C3).
    • Absence of gross hematuria episodes (suggests less intense inflammatory episodes but more insidious chronic damage).

• Survival:

  • Approximately 20-40% of patients with IgAN progress to ESRD within 10-20 years of diagnosis.
  • Overall life expectancy is reduced in patients who progress to ESRD, largely due to cardiovascular complications.

• Quality of Life:

  • Can be significantly impacted by symptoms of CKD, side effects of immunosuppressive medications, and the need for renal replacement therapy. Regular monitoring and aggressive management are key to maintaining quality of life.

Prevention

• Primary: No known specific primary prevention for IgAN. General healthy lifestyle and management of infections may be beneficial for overall health but do not prevent the autoimmune process.

• Secondary: Early diagnosis and aggressive management of modifiable risk factors can slow disease progression:

  • Early identification of proteinuria and hypertension.
  • Prompt initiation of RAS blockade and SGLT2 inhibitors.
  • Control of blood pressure per target guidelines.

• Tertiary: Preventing complications and managing ESRD:

  • Close monitoring and management of CKD complications (anemia, bone disease, cardiovascular risk factors).
  • Timely referral for renal replacement therapy options when ESRD develops.
  • Careful selection and monitoring of immunosuppressants to mitigate side effects.

Special Populations

• Pediatric:

  • Often presents with gross hematuria following URIs.
  • Crescentic IgAN occurs more frequently than in adults.
  • Prognosis generally better than in adults, but long-term follow-up is essential as progression to ESRD can occur.
  • Treatment with RAS blockade and supportive care is similar. Steroid therapy and other immunosuppressants are used for rapidly progressive or severe cases (e.g., nephrotic range proteinuria, RPGN).

• Geriatric:

  • Higher incidence of advanced CKD at presentation.
  • Comorbidities and polypharmacy are common, increasing risk of medication side effects.
  • Immunosuppressive therapy requires careful consideration due to increased infection risk and other adverse events.
  • Prognosis is generally worse due to older age, higher comorbidity burden, and often more advanced kidney damage.

• Pregnancy:

  • Pregnancy in women with IgAN should be managed as high-risk.
  • Increased risk of preeclampsia, hypertension, preterm birth, and accelerated decline in GFR, especially if baseline renal function is impaired or proteinuria is significant (>1 g/day).
  • RAS inhibitors are contraindicated in pregnancy; discontinue before conception. Labetalol, nifedipine, and methyldopa are safe antihypertensive alternatives.
  • Close monitoring of BP, proteinuria, and renal function throughout pregnancy.

• Comorbidities:

  • Liver Cirrhosis: Often associated with secondary IgAN. Management focuses on treating the underlying liver disease and supportive renal care.
  • Celiac Disease: Screen for celiac disease in IgAN patients with GI symptoms. Gluten-free diet may improve renal outcomes in some.
  • Obesity: Exacerbates kidney disease progression. Weight loss is important.
  • Diabetes: Increases cardiovascular and renal risk. Aggressive management of glycemic control is essential. SGLT2 inhibitors are beneficial in both conditions.

Clinical Pearls

• Diagnostic:

  • Think IgAN in young adults with recurrent gross hematuria, especially 1-3 days after an infection (synpharyngitic hematuria).
  • Kidney biopsy is essential; IgA deposition is diagnostic, but context with clinical and histological features (Oxford classification) is crucial for prognosis and treatment decisions.
  • Always consider secondary causes of IgA nephropathy, especially in older patients or those with systemic symptoms.

• Treatment:

  • RAS blockade and SGLT2 inhibitors are first-line for nearly all patients with proteinuria and/or CKD.
  • Shared decision-making is critical when considering immunosuppression (systemic steroids, targeted-release budesonide) due to potential side effects and varying patient preferences.
  • Target BP rigorously: aim for <120/80 mmHg if tolerated, according to current guidelines.
  • Do not delay biopsy in patients with suspected RPGN or rapid decline in eGFR.

• Pitfalls:

  • Mistaking IgAN for acute post-streptococcal glomerulonephritis (APSG): distinguish by timing of hematuria onset after infection (IgAN: 1-3 days; APSG: 1-3 weeks) and C3 levels (IgAN: normal C3; APSG: low C3).
  • Underestimating the risk of progression in seemingly "mild" cases; even with preserved GFR, significant proteinuria warrants treatment.
  • Overtreating with immunosuppression in patients with extensive chronicity (high T score on biopsy) where benefits are unlikely to outweigh risks.
  • Failure to address cardiovascular risk factors, which are major contributors to morbidity and mortality in CKD.

Recent Updates

• Guidelines:

  • KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases: Recommended SGLT2 inhibitors for patients with CKD and albuminuria (UACR ≥ 200 mg/g), regardless of diabetes status. Emphasized personalized steroid use and the role of novel therapies.
  • Recognition of targeted-release budesonide (Nefecon) as an approved treatment option for IgAN at risk of progression.

• Evidence:

  • PROTECT Study: Demonstrated reduction in proteinuria and stabilization of eGFR with targeted-release budesonide (Nefecon) in IgAN.
  • DAPA-CKD and EMPA-KIDNEY Trials: Confirmed the kidney protective effects of SGLT2 inhibitors in patients with CKD, including those with IgAN, further solidifying their role in standard care.

• Controversies:

  • Optimal duration and dosing of systemic corticosteroids: While guidelines suggest a course of 6-9 months, there's ongoing debate regarding the optimal balance between efficacy and minimizing side effects.
  • Role of tonsillectomy: Some evidence from Asian cohorts suggests benefit in reducing disease progression, especially in patients with recurrent gross hematuria. However, its routine use is not universally recommended, and more robust Western data are needed.
  • Emerging therapies: Ongoing research into complement inhibitors, B-cell depleting agents, and other novel targets. Their precise role in standard treatment algorithms is yet to be fully defined.

Key References

• Guidelines:

  • Kidney Disease: Improving Global Outcomes (KDIGO) 2021 Clinical Practice Guideline for the Management of Glomerular Diseases. Kidney Int. 2021 Oct;100(4S):S1-S276.
  • KDIGO Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2012;3(1):1–150. (Updates expected)

• Studies:

  • J. Barratt et al., "Targeted-release budesonide versus placebo in patients with IgA nephropathy (NefIgArd): a multicentre, double-blind, randomised, phase 3 trial," Lancet. 2023 Feb 11;401(10380):1016-1029. (NefIgArd Study)
  • H. J. L. Heerspink et al., "Dapagliflozin in Patients with Chronic Kidney Disease," N Engl J Med. 2020 Oct 22;383(15):1436-1446. (DAPA-CKD Trial)
  • M. Estirado et al., "Immunosuppression in IgA nephropathy: from randomized controlled trials to real-world experience," Clin Kidney J. 2021 Nov 22;15(3):477-486.

• Reviews:

  • J. Barratt and J. Feehally, "IgA nephropathy," J Am Soc Nephrol. 2005 Sep;16(9):2088-97.
  • F. M. Rizk et al., "The First Autoimmune Glomerulonephritis: IgA Nephropathy," Adv Chronic Kidney Dis. 2019 Mar;26(2):100-108.
  • R. P. Coppo, "Therapeutic approaches for IgA nephropathy," Semin Nephrol. 2013 May;33(3):370-82.

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Disclaimer: This information is intended for educational purposes only and does not constitute medical advice. It is essential for clinicians to exercise independent medical judgment and consider individual patient factors when making diagnostic and treatment decisions. Always refer to the latest evidence-based guidelines and consult with specialists as appropriate. The practice of medicine is constantly evolving, and information may become outdated.