IgA nephropathy, also known as Berger’s disease, is the most common primary glomerulonephritis worldwide. It is characterized by the deposition of IgA1-containing immune complexes in the glomerular mesangium, leading to mesangial proliferation, inflammation, and subsequent glomerular injury.
The hallmark of the disease is mesangial deposition of IgA, often accompanied by complement component C3, leading to a form of immune complex-mediated glomerulonephritis.
Pathophysiology
IgA nephropathy is a multi-hit immune-mediated disease with the following mechanisms:
- Increased synthesis of aberrantly glycosylated IgA1 in mucosal immune sites (especially after infections).
- Formation of autoantibodies (usually IgG or IgA) against galactose-deficient IgA1.
- Immune complex formation and deposition in the glomerular mesangium.
- Mesangial cell activation, cytokine release, and complement activation (especially via the alternative and lectin pathways).
- Resulting in inflammation, cellular proliferation, and eventually glomerular fibrosis and sclerosis.
Etiology & Risk Factors
The exact cause remains unclear, but several contributing factors are recognized:
Immunological Factors
- Overproduction of galactose-deficient IgA1.
- Autoantibody formation against IgA1.
- Defective mucosal immune regulation.
Genetic & Environmental Factors
- Familial clustering—suggests genetic predisposition.
- Common in East Asians and Caucasians; rare in Black populations.
- Males are affected more frequently (2:1 ratio).
- Most common in teens to early 30s.
Associated Conditions
- Liver diseases (e.g., cirrhosis).
- Celiac disease.
- Infections (especially respiratory or gastrointestinal).
- Dermatitis herpetiformis.
- HIV and other immune dysregulation syndromes.
Clinical Presentation
Common Symptoms
- Recurrent episodes of gross hematuria, often following upper respiratory tract infections (synpharyngitic hematuria).
- Asymptomatic microscopic hematuria with or without mild proteinuria.
- Coca-Cola or tea-colored urine.
- Foamy urine (indicating proteinuria).
- Peripheral edema (due to nephrotic-range proteinuria).
- Hypertension.
Other Presentations
- Rapidly progressive glomerulonephritis (RPGN) in severe cases.
- Flank pain and fever may occur during gross hematuria episodes.
Diagnosis
Laboratory Investigations
- Urinalysis:
- Microscopic hematuria (with dysmorphic RBCs and RBC casts).
- Mild to moderate proteinuria (<1 g/day; nephrotic-range in severe cases).
- Serum studies:
- Normal complement levels (C3 and C4).
- Elevated serum IgA in ~50% of patients.
Definitive Diagnosis
- Renal biopsy:
- Mesangial proliferation and expansion.
- Granular mesangial deposits of IgA and C3 on immunofluorescence.
- Possible presence of crescents in progressive disease.
Prognostic Indicators of Poor Outcome
- Persistent proteinuria > 0.5–1 g/day.
- Hypertension.
- Elevated serum creatinine at diagnosis.
- Microscopic hematuria > 6 months.
- Histological findings: glomerular sclerosis, interstitial fibrosis, and crescent formation.
Treatment and Management
General Approach
- No definitive cure—management aims to slow disease progression and control complications.
- Patients with isolated microscopic hematuria and preserved renal function may only require observation.
Pharmacologic Therapy
- ACE inhibitors (ACEIs) or ARBs:
- First-line in patients with proteinuria >0.5–1 g/day, hypertension, or reduced renal function.
- Corticosteroids:
- Considered in patients with persistent proteinuria >1 g/day despite optimized supportive therapy.
- Immunosuppressants (e.g., cyclophosphamide or mycophenolate mofetil):
- Reserved for rapidly progressive disease or crescentic nephritis.
- Fish oil (omega-3 fatty acids):
- May have anti-inflammatory benefits in mild cases.
Renal Transplantation
- May be required in end-stage renal disease (ESRD).
- Recurrence of IgA nephropathy in the transplanted kidney can occur but usually with a milder course.
Complications
- Hypertension: due to chronic glomerular injury.
- Chronic kidney disease (CKD): slow progression over years.
- Acute kidney injury (AKI): in severe cases, especially RPGN.
- Nephrotic syndrome: in patients with heavy proteinuria.
- Cardiovascular disease: due to associated hypertension and dyslipidemia.
- End-stage renal disease (ESRD): occurs in 20–40% within 20 years in high-risk patients.
High-Yield Clinical Pearls
- IgA nephropathy commonly follows an upper respiratory infection within 1–2 days, distinguishing it from post-streptococcal glomerulonephritis (which occurs 1–3 weeks later).
- Normal complement levels help differentiate from other immune complex-mediated glomerulonephritides (like lupus nephritis).
- Renal biopsy is essential for diagnosis.
- Persistent proteinuria is the most important modifiable risk factor for progression.
- Use RAAS blockers early in patients with proteinuria to reduce glomerular damage.
