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BASICS

Description

  • PIGN is an immune complex disease associated with nonrenal infections by bacteria such as Streptococcus and Staphylococcus.
  • Most common form: poststreptococcal glomerulonephritis (PSGN), predominantly affects children.
  • Clinical features range from asymptomatic to acute nephritic syndrome: gross hematuria, proteinuria, edema, hypertension, acute kidney injury.

Epidemiology

  • Declining globally due to improved hygiene.
  • Estimated 470,000 new PSGN cases annually worldwide.
  • PSGN remains the most common cause of acute nephritis in children globally, especially in developing countries (~97%).
  • Recent increase in nonstreptococcal PIGN cases in adults.

Etiology and Pathophysiology

  • Caused by nephritogenic strains of bacteria:

  • 95% due to group A β-hemolytic Streptococcus (GAS).

  • Staphylococcus aureus (including MRSA), coagulase-negative Staph.
  • Gram-negative bacteria: E. coli, Yersinia, Pseudomonas, Haemophilus.
  • Rare viral, fungal, helminthic, protozoal causes.
  • Pathogenesis:
  • Circulating immune complexes with bacterial antigens deposit in glomeruli.
  • Complement activation (alternative and lectin pathways) causes inflammation.
  • Nephritis-associated plasmin receptor (NAPlr) and streptococcal pyrogenic exotoxin B (SPE B) promote injury.

Risk Factors

  • Children 5-12 years.
  • Older adults (>65) with immunocompromise (diabetes, alcohol abuse).

General Prevention

  • Early antibiotics for streptococcal/staphylococcal infections (efficacy uncertain).
  • Improved hygiene and respiratory etiquette.
  • Prophylactic penicillin in closed communities/household contacts where PIGN is prevalent.

DIAGNOSIS

History

  • Antecedent GAS pharyngitis or skin infection.
  • Acute nephritic syndrome: hematuria (tea/cola-colored urine), edema, hypertension, oliguria.
  • Latent period: 1-3 weeks post-pharyngitis, 3-6 weeks post-skin infection.
  • Adult PIGN often follows staphylococcal infections; sometimes no identifiable preceding infection.

Physical Exam

  • Fever (40-50%).
  • Edema (2/3 adults), less common in children.
  • Hypertension (80-90%), mild to severe.
  • Rare hypertensive encephalopathy.
  • Rare pulmonary edema, encephalopathy, seizures.

Differential Diagnosis

  • MPGN (persistent nephritis, hypocomplementemia >4-6 weeks).
  • Lupus nephritis, Henoch-Schönlein purpura nephritis.
  • IgA nephropathy (recurs, normal complements).
  • IgA-dominant acute PIGN (poststaphylococcal, no prior renal disease).
  • Pauci-immune crescentic GN in elderly (ANCA testing recommended).

Diagnostic Tests & Interpretation

Initial Tests

  • Urinalysis: hematuria (gross in 25-60%, microscopic in subclinical), RBC casts, pyuria.
  • Proteinuria in ~90% (nephrotic range uncommon in children).
  • Decreased GFR, elevated creatinine in 25-83% (more common in adults).

Follow-Up Tests

  • Culture: positive throat/skin cultures in ~25% only.
  • Complement: depressed C3 and CH50 (90% children, fewer adults), normal C2, C4.
  • Serology: elevated ASO, anti-DNAse B, anti-hyaluronidase titers (>95% pharyngitis, 80% skin infections).

Diagnostic Procedures

  • Renal biopsy (rare in children, recommended in adults):
  • Light microscopy: diffuse proliferative GN, endocapillary proliferation, neutrophils, "starry sky" deposits.
  • Crescent formation uncommon but indicates poor prognosis.
  • Immunofluorescence: granular C3 and IgG deposits.
  • Electron microscopy: subepithelial "hump"-shaped electron-dense deposits (immune complexes).

TREATMENT

Medication

  • No specific therapy for PIGN.
  • Steroids considered if >30% crescents on biopsy.
  • Supportive management:
  • Salt/water restriction.
  • Loop diuretics.
  • Calcium channel blockers/ACE inhibitors for hypertension.
  • Antibiotics for ongoing infection.

Surgery/Other Procedures

  • Acute dialysis required in ~50% elderly patients.

Admission

  • Hospitalization for elderly at risk of complications (heart failure exacerbation).

ONGOING CARE

Follow-up

  • Repeat urinalysis for clearance of hematuria/proteinuria.
  • Consider alternative diagnoses if no improvement in 2 weeks.

Diet

  • Renal diet if dialysis required.

PROGNOSIS

  • Excellent recovery in >90% children.
  • Adults, especially elderly with comorbidities, risk hypertension, proteinuria, renal insufficiency long-term.
  • Complete remission in adults 26-56%, prognosis worsening since 1990s.
  • Risk factors for ESRD: diabetes, high creatinine, severe glomerular disease (crescents).

COMPLICATIONS

  • Volume overload related: hypertension, pulmonary edema.
  • Recurrent proteinuria, renal insufficiency rare.

CLINICAL PEARLS

  • PIGN is immune complex disease after infection, mainly group A Streptococcus.
  • Presentation: gross hematuria, proteinuria, edema, HTN, AKI.
  • Treatment is supportive; steroids used in crescentic disease.
  • Persistent nephritis and low C3 >2 weeks prompt evaluation for other GN causes.

REFERENCES

  1. Hunt EAK, Somers MJG. Infection-related glomerulonephritis. Pediatr Clin North Am. 2019;66(1):59-72.
  2. Nasr SH, Radhakrishnan J, D'Agati VD. Bacterial infection-related glomerulonephritis in adults. Kidney Int. 2013;83(5):792-803.
  3. Nadasdy T, Hebert LA. Infection-related glomerulonephritis: understanding mechanisms. Semin Nephrol. 2011;31(4):369-375.