# IgA Nephropathy

> IgA nephropathy for NEET-PG Paediatrics: synpharyngitic haematuria, mesangial IgA deposits, Oxford classification and how it differs from post-infectious GN.

- Canonical URL: https://prepelephant.com/topics/neet-pg/paediatrics/iga-nephropathy
- Exam / course: NEET-PG · Subject: Paediatrics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Brenner and Rector's The Kidney; Oxford Classification of IgA Nephropathy
- How to cite: "IgA Nephropathy", PrepElephant, https://prepelephant.com/topics/neet-pg/paediatrics/iga-nephropathy

## Direct answer

IgA nephropathy is the commonest primary glomerulonephritis worldwide, defined by mesangial IgA deposits on immunofluorescence. In children it often presents as macroscopic haematuria within one to three days of an upper respiratory infection, or as persistent microscopic haematuria found on screening. Most children have a benign course, but persistent proteinuria and hypertension predict progression, and ACE inhibitors are the mainstay of treatment.

## What you must remember

- **Synpharyngitic haematuria:** macroscopic haematuria within one to three days of an upper respiratory infection, often recurring with later infections.
- **Immunofluorescence:** dominant mesangial IgA, usually with C3; electron microscopy shows electron-dense mesangial deposits.
- **Oxford classification:** scores mesangial hypercellularity, endocapillary hypercellularity, segmental sclerosis, tubular atrophy and interstitial fibrosis, and crescents (MEST-C) to predict outcome.
- **Adverse markers:** persistent proteinuria, hypertension and falling eGFR predict progression to kidney failure.
- **Complement:** normal C3 in IgA nephropathy, unlike post-streptococcal GN, where C3 is low and recovers within weeks.
- **Mimic:** IgA vasculitis (Henoch-Schonlein purpura) shares the same IgA deposits, but adds purpura, arthralgia and abdominal pain.
- **Treatment:** renin-angiotensin blockade for proteinuria; immunosuppression reserved for progressive disease under specialist care.
- **Prognosis:** most children do well, though a proportion progress to kidney failure in adult life.

## A pathway from screening to risk-based treatment

A 10-year-old has recurrent visible haematuria after colds, with normal blood pressure and a urine protein-creatinine ratio of about 0.3 mg/mg. The pathway decides whether he needs a biopsy and how aggressively to treat.

1. **Confirm glomerular bleeding.** Dysmorphic red cells and casts on urine microscopy support a glomerular source.
2. **Quantify protein and pressure.** Protein-creatinine ratio, creatinine, eGFR and blood pressure at each visit.
3. **Biopsy when indicated.** Persistent proteinuria, hypertension or reduced eGFR calls for biopsy with Oxford scoring.
4. **Exclude mimics.** Check for purpura and arthralgia suggesting IgA vasculitis, and low complement suggesting other disease.
5. **Start supportive therapy.** ACE inhibitor or ARB for significant proteinuria, with salt restriction and blood pressure control.
6. **Consider immunosuppression.** Reserved for heavy proteinuria or declining function despite supportive care.
7. **Follow up for years.** Repeat urine and renal function tests to catch late progression.

## Where the exam tries to catch you

IgA questions often hinge on complement levels and the nature of the proteinuria.

- **Trap:** labelling post-viral haematuria as post-streptococcal GN without checking complement. **Correct:** IgA nephropathy has normal C3, whereas low complement points to PSGN, lupus or membranoproliferative disease.
- **Trap:** starting steroids routinely for mild IgA nephropathy. **Correct:** supportive RAS blockade comes first, and immunosuppression is reserved for progressive disease.
- **Trap:** dismissing isolated haematuria as harmless without a biopsy. **Correct:** persistent proteinuria or reduced eGFR calls for biopsy and classification.

## Frequently asked questions

### Which immunofluorescence finding defines IgA nephropathy?

Dominant or co-dominant mesangial IgA deposits on immunofluorescence define IgA nephropathy. These deposits are usually accompanied by C3 and are seen on renal biopsy, often with electron-dense mesangial deposits on electron microscopy.

### How does IgA nephropathy differ from post-streptococcal glomerulonephritis?

IgA nephropathy differs from post-streptococcal glomerulonephritis by its normal complement levels and its mesangial IgA deposits. Post-streptococcal GN has low C3 that normalises within about eight weeks and subepithelial humps on electron microscopy.

### What features predict poor prognosis in childhood IgA nephropathy?

Persistent proteinuria, hypertension, reduced eGFR and higher Oxford scores for segmental sclerosis, tubular atrophy and crescents predict poor prognosis in childhood IgA nephropathy. These features guide the intensity of treatment and the frequency of follow-up.

### Why is the complement level important in IgA nephropathy?

The complement level is important in IgA nephropathy because it helps separate this disease from post-streptococcal GN, lupus nephritis and membranoproliferative GN. Normal C3 supports IgA nephropathy, while a low C3 needs a different diagnostic pathway.