Renal/Urology · PANCE / PANRE

IgA Nephropathy

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Most common primary glomerulonephritis; mesangial IgA deposits with synpharyngitic hematuria.

Also known as: IgA nephropathy, Berger disease, IgAN

Overview

A primary glomerular disease defined by predominant mesangial IgA deposition on immunofluorescence, typically presenting with recurrent macroscopic hematuria concurrent with or shortly after mucosal infection (synpharyngitic hematuria) or with asymptomatic microscopic hematuria and proteinuria.

Epidemiology

Most common primary glomerulonephritis worldwide. Peak incidence in 2nd-3rd decade. Male predominance (2:1). More common in Asian and white populations; rare in Black patients.

Try two board-style IgA Nephropathy questions

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Question 1RenalMedium
A 25-year-old man presents with one day of painless gross hematuria that began the same day he developed a sore throat and rhinorrhea. He has had two similar episodes in the past two years, each coinciding with an upper respiratory infection. Exam is unremarkable. Labs show creatinine 1.4 mg/dL and proteinuria 1.5 g/day. Urinalysis shows dysmorphic RBCs. Renal biopsy demonstrates mesangial proliferation with IgA deposits on immunofluorescence. Which of the following is the most likely diagnosis?
  • APost-streptococcal glomerulonephritis
  • BThin basement membrane disease
  • CAlport syndrome
  • DIgA nephropathy
Reveal answer & full explanation
Correct answer: D — IgA nephropathy
  • APost-streptococcal glomerulonephritis
  • BThin basement membrane disease
  • CAlport syndrome
  • DIgA nephropathy✓

Why IgA nephropathy is correct

  • IgA nephropathy is the most common primary glomerulonephritis (GN) worldwide
  • KEY DISTINGUISHING FEATURE: synpharyngitic hematuria — gross hematuria occurs concurrent with or within days of a URI, NOT weeks later
  • Biopsy shows mesangial IgA deposits on immunofluorescence
  • Treatment: ACE inhibitor (ACEi) / angiotensin receptor blocker (ARB) if proteinuria >1 g/day; corticosteroids plus supportive care for rapidly progressive disease

Why the others are wrong

  • A) Post-streptococcal glomerulonephritis — hematuria occurs 2–3 weeks after strep throat or 4–6 weeks after strep impetigo, not concurrent with the URI
  • B) Thin basement membrane disease — benign familial hematuria causes persistent MICROSCOPIC hematuria with normal creatinine and no significant proteinuria, and biopsy shows a thinned GBM without IgA
  • C) Alport syndrome — hereditary (usually X-linked) collagen IV disease with sensorineural hearing loss and ocular defects; biopsy shows basket-weave GBM splitting, not mesangial IgA
Question 2RenalEasy
A 22-year-old male presents with hematuria 2 days after a viral upper respiratory infection (URI). He had a similar episode 6 months ago, also after a URI. Renal biopsy shows mesangial expansion with IgA deposits on immunofluorescence. C3 and C4 are normal. Which of the following is the most likely diagnosis?
  • APost-streptococcal glomerulonephritis
  • BIgA nephropathy
  • CAlport syndrome
  • DLupus nephritis
Reveal answer & full explanation
Correct answer: B — IgA nephropathy
  • APost-streptococcal glomerulonephritis
  • BIgA nephropathy✓
  • CAlport syndrome
  • DLupus nephritis

Why IgA nephropathy is correct

  • IgA nephropathy (Berger disease) is the most common primary glomerulonephritis worldwide.
  • Episodic hematuria occurs 1–3 days after a URI ("synpharyngitic" — concurrent with the URI, not after a latent period).
  • Complement levels (C3, C4) are characteristically normal.
  • Renal biopsy shows mesangial expansion with IgA deposits on immunofluorescence.
  • Recurrent gross hematuria triggered by mucosal infections in a young adult is the classic presentation.

Why the others are wrong

  • Post-streptococcal glomerulonephritis — right-concept-wrong-setting: has a latent period of 1–3 weeks after pharyngitis and shows low C3 from complement consumption, unlike the synpharyngitic timing and normal complement here.
  • Alport syndrome — confused-with hereditary nephritis; features sensorineural hearing loss and ocular abnormalities and is not associated with recurrent post-URI flares.
  • Lupus nephritis — anchoring on immune-complex nephritis; requires systemic lupus findings and typically shows low complement levels.

Additional high-yield points

  • Henoch-Schönlein purpura (IgA vasculitis) is the systemic form with IgA deposits in skin (palpable purpura), GI tract (abdominal pain), joints, and kidneys.
  • Treatment: ACE inhibitor or ARB for proteinuria; corticosteroids for active disease with declining GFR.
  • 25–30% progress to end-stage renal disease (ESRD) over 25 years.
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Risk factors

  • Family history of IgA nephropathy
  • Asian or white ethnicity
  • Mucosal infections (URIs, GI) — trigger flares
  • Celiac disease, IBD, cirrhosis (secondary IgA deposition)
  • Henoch-Schönlein purpura (IgA vasculitis) — systemic form

Pathophysiology

Galactose-deficient IgA1 (Gd-IgA1) is recognized by anti-glycan autoantibodies, forming circulating immune complexes that deposit in the mesangium. Mesangial cell proliferation, complement activation (alternative pathway), and cytokine release drive injury. Progressive disease causes glomerulosclerosis and tubulointerstitial fibrosis.

Clinical presentation

Symptoms

  • Gross hematuria within 1-3 days of URI, GI infection, or vigorous exercise (synpharyngitic)
  • Asymptomatic microscopic hematuria (most common presentation)
  • Flank pain during gross hematuria episodes
  • Edema and hypertension if nephrotic-range proteinuria or significant impairment

Signs / physical exam

  • Often normal physical exam
  • Hypertension (more common with progression)
  • Edema if heavy proteinuria
  • Skin/joint findings if IgA vasculitis variant

Classic findings

Recurrent episodes of cola-colored urine within 24-72 hours of a URI = synpharyngitic hematuria of IgA nephropathy.

Differential diagnosis

  • Post-streptococcal GN — Hematuria 1-3 weeks after strep infection (not same-day); low C3; positive ASO; usually self-limited
  • Thin basement membrane disease — Benign familial hematuria; isolated microhematuria; thin GBM on EM; preserved function
  • Alport syndrome — X-linked; hematuria + sensorineural hearing loss + ocular findings; type IV collagen mutation
  • Henoch-Schönlein purpura (IgA vasculitis) — Same pathology + palpable purpura, arthralgia, abdominal pain; usually in children
  • Lupus nephritis — Systemic SLE features; full-house IF pattern (vs IgA-dominant)
  • Urinary tract source of hematuria — Eumorphic RBCs, no casts, no proteinuria; cystoscopy and urology workup

Diagnostic workup

Diagnostic criteria

Definitive diagnosis requires kidney biopsy showing dominant or co-dominant mesangial IgA deposition on immunofluorescence with mesangial proliferation on light microscopy. Oxford MEST-C score (mesangial hypercellularity, endocapillary, segmental sclerosis, tubular atrophy, crescents) prognosticates.

Labs

  • Urinalysis with microscopy — hematuria with dysmorphic RBCs, sometimes RBC casts; mild proteinuria
  • Spot UPCR — proteinuria quantification (>1 g/day = poor prognosis)
  • BMP with creatinine and eGFR
  • Serum IgA elevated in ~50% (nonspecific, not diagnostic)
  • Normal complement (helps distinguish from post-strep, lupus, MPGN)
  • Negative ANA, ANCA, anti-GBM (to exclude alternatives)

Imaging

  • Renal ultrasound to assess size and exclude obstruction in presence of gross hematuria

Diagnostic algorithm

FeatureIgA NephropathyPost-Strep GN
Timing after infection1-3 days (synpharyngitic)1-3 weeks (latent)
Complement (C3)NormalLow
SerologyElevated IgA (~50%)ASO, anti-DNase B positive
CourseChronic, relapsingSelf-limited (typically)
PopulationYoung adults, Asian/whiteChildren, post-strep pharyngitis or impetigo
Biopsy IFMesangial IgAGranular IgG/C3, subepithelial 'humps'
Long-term prognosis20-40% ESRD over 20 yrExcellent in children, worse in adults
Distinguishing IgA nephropathy from post-streptococcal GN — timing, complement, and serology.

Treatment

First-line

  • BP control with ACEi (lisinopril, ramipril) or ARB (losartan, valsartan) — first-line; titrate to maximally tolerated dose
  • SGLT2 inhibitor — dapagliflozin or empagliflozin — added for proteinuria reduction and renal protection (KDIGO 2024)
  • Target proteinuria <0.5-1 g/day; BP <120/80
  • Lifestyle: smoking cessation, sodium restriction, weight management
  • Cardiovascular risk reduction: statin if indicated

Second-line / adjunct

  • Sparsentan (dual endothelin/angiotensin receptor antagonist) — for proteinuria >1 g/day despite RAAS blockade
  • Targeted-release budesonide (Nefecon) — gut-restricted glucocorticoid for high-risk patients with persistent proteinuria
  • Systemic glucocorticoids — controversial; consider in rapidly progressive disease (KDIGO suggests selective use)
  • Crescentic IgA nephropathy: cyclophosphamide + steroids ± plasma exchange
  • Tonsillectomy: variable evidence, more common in Asian practice
  • RRT/transplant for ESRD — IgA can recur in allograft (~30%)

Complications

  • Progression to CKD/ESRD in 20-40% over 20 years
  • Rapidly progressive (crescentic) GN — rare but severe
  • Acute kidney injury from gross hematuria episodes (tubular obstruction by RBC casts)
  • Hypertensive complications
  • Recurrence post-transplant

PANCE pearls

  • Synpharyngitic hematuria (within 1-3 days of URI) = IgA. Post-streptococcal GN takes 1-3 weeks.
  • Normal complement levels distinguish IgA from post-strep, lupus, and MPGN.
  • MEST-C score guides prognosis: M1, E1, S1, T1-2, C1-2 each carry worse outcome.
  • IgA vasculitis (Henoch-Schönlein purpura) is the systemic form: same renal pathology + palpable purpura, arthritis, abdominal pain.
  • Persistent proteinuria >1 g/day is the strongest predictor of progression.

References

  • KDIGO 2021/2024 — KDIGO 2021 Guideline for Management of Glomerular Diseases; 2024 IgA Nephropathy Update
  • PROTECT — Sparsentan in IgA Nephropathy (Heerspink et al., Lancet 2023)
  • NefIgArd — Targeted-release Budesonide for IgA Nephropathy (Barratt et al., Lancet 2023)
  • Oxford Classification — Oxford Classification of IgA Nephropathy: 2016 Update (Trimarchi et al., Kidney Int 2017)

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Commonly confused with

vs Post-Streptococcal Glomerulonephritis

Related Renal/Urology diagnoses

Acute Kidney Injury (AKI)Chronic Kidney Disease (CKD)End-Stage Renal Disease and DialysisNephrotic SyndromeNephritic SyndromeAcute Tubular Necrosis (ATN)Acute Interstitial Nephritis (AIN)Post-Streptococcal Glomerulonephritis (PSGN)Autosomal Dominant Polycystic Kidney Disease (ADPKD)Urolithiasis (Kidney Stones)Acute Cystitis (Uncomplicated UTI)Acute PyelonephritisRenal Cell Carcinoma (RCC)Bladder Cancer

Differentials & related conditions

IgA Vasculitis (Henoch-Schönlein Purpura)Lupus Nephritis

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.