Immune complex GN 1-3 weeks after group A strep pharyngitis or impetigo.
Also known as: PSGN, post-streptococcal GN, acute post-infectious GN
Overview
An immune complex-mediated glomerulonephritis occurring 1-3 weeks after infection with nephritogenic strains of group A beta-hemolytic streptococcus (GAS), typically pharyngitis or skin infection (impetigo). Presents with classic nephritic syndrome.
Epidemiology
Most common cause of acute glomerulonephritis in children worldwide. Peak age 4-12 years. Incidence has declined in developed countries with early antibiotic treatment of strep infections. Adults can be affected, with worse prognosis. Outbreaks may follow skin infection epidemics.
🔒 Free preview limit reached
Keep reading — start your free trial
You've read your 2 free diagnosis previews. Create your free account to unlock the full Post-Streptococcal Glomerulonephritis (PSGN) outline — plus all 514 diagnoses, 3,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
Nephritogenic strains of GAS (M types 1, 4, 12 in pharyngitis; M types 47, 49, 55 in impetigo) produce antigens (notably streptococcal pyrogenic exotoxin B and nephritis-associated plasmin receptor) that form circulating immune complexes or deposit in situ in subepithelial glomerular sites. Complement activation (alternative pathway predominantly) drives inflammation, mesangial and endothelial proliferation.
Clinical presentation
Symptoms
Abrupt onset of tea-colored or cola-colored urine (gross hematuria) 1-3 weeks after pharyngitis or 3-6 weeks after impetigo
Periorbital edema, especially in the morning
Decreased urine output
Headache and malaise from hypertension
Children may have nonspecific symptoms initially
Signs / physical exam
Hypertension (50-90% of children)
Periorbital and dependent edema
Tea-colored or smoky urine
Mild tenderness over flanks (uncommon)
Healed strep infection — pharyngeal exam often normal at presentation
Classic findings
Cola-colored urine + periorbital edema + hypertension in a child 1-3 weeks after sore throat or impetigo = classic PSGN.
Differential diagnosis
IgA nephropathy — Synpharyngitic hematuria (within 1-3 days, not 1-3 weeks); normal complement; recurrent episodes
Other post-infectious GN — After staph, gram-negative, or viral infections; similar pathology
Diagnostic workup
Diagnostic criteria
Clinical diagnosis: nephritic syndrome + recent strep infection + low C3 + positive streptococcal serology. Biopsy reserved for atypical presentations (persistent low C3 >8 weeks, severe AKI, RPGN features) and shows endocapillary proliferative GN with subepithelial 'humps' on EM and granular IgG/C3 on IF.
Labs
Urinalysis: hematuria with dysmorphic RBCs and RBC casts, mild-moderate proteinuria (typically subnephrotic), pyuria
BMP: elevated creatinine, sometimes hyperkalemia
Low C3 (90%), normal C4 — pathognomonic complement pattern
Streptococcal serologies: ASO (positive in 60-80% after pharyngitis but less so after skin infection), anti-DNase B (more sensitive after impetigo), anti-hyaluronidase, anti-streptokinase
Throat culture or skin culture (often negative by time of GN presentation)
Streptozyme test combines multiple antibodies
Imaging
Renal ultrasound usually unnecessary; normal or mildly enlarged kidneys
Diagnostic algorithm
Feature
PSGN
IgA Nephropathy
Latency after infection
1-3 wk (pharyngitis); 3-6 wk (skin)
1-3 days (synpharyngitic)
Age
Children 4-12 yr (mainly)
Young adults
Complement C3
Low (resolves in 6-8 wk)
Normal
Serology
ASO, anti-DNase B positive
Elevated IgA (~50%)
Course
Self-limited (children); residual in adults
Chronic, relapsing
Biopsy IF
Granular IgG/C3, 'humps' on EM
Mesangial IgA deposits
Prognosis
>95% recovery in children
20-40% ESRD over 20 yr
Distinguishing post-streptococcal GN from IgA nephropathy — the two most common pediatric/young adult nephritic presentations.
Treatment
First-line
Supportive care — most cases resolve spontaneously
Sodium and fluid restriction for volume overload
Loop diuretic — furosemide — for edema and hypertension
Antihypertensives: CCB (amlodipine) or ACEi (if renal function stable); hydralazine or nicardipine for hypertensive emergency
Antibiotics (penicillin V, amoxicillin, or erythromycin if allergic) if active strep infection still present — does NOT alter renal course but limits transmission
Second-line / adjunct
Dialysis temporarily if severe AKI with hyperkalemia, uremia, or refractory volume overload (rare)
Glucocorticoids only if biopsy shows crescents (atypical RPGN course)
Monitor C3 — should normalize within 6-8 weeks; persistent low C3 should prompt alternative diagnosis (MPGN, lupus)
Family screening of household contacts for active strep infection
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. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.