Acute Poststreptococcal Glomerulonephritis (PSGN) in Children
Introduction to Acute Poststreptococcal Glomerulonephritis (PSGN) in Children
Acute Poststreptococcal Glomerulonephritis (PSGN) is an immune-mediated renal disease that occurs following infection with specific strains of group A beta-hemolytic streptococci.
- Epidemiology:
- Incidence: Decreasing in developed countries, but still common in developing nations
- Age: Most common in children aged 3-12 years
- Gender: Males are more frequently affected than females (2:1 ratio)
- Etiology:
- Primarily caused by "nephritogenic" strains of group A beta-hemolytic streptococci
- Most common serotypes: M types 1, 4, 12, 25, 49, 55, 57, and 60
- Can follow streptococcal throat infection (pharyngitis) or skin infection (impetigo)
- Latency period:
- 1-2 weeks after streptococcal pharyngitis
- 3-6 weeks after streptococcal skin infection
Pathophysiology of PSGN
PSGN is an immune complex-mediated disease involving the glomeruli of the kidneys.
- Immune complex formation:
- Streptococcal antigens (e.g., streptococcal pyrogenic exotoxin B, NAPlr) interact with host antibodies
- Immune complexes deposit in the glomeruli
- Complement activation:
- Immune complexes activate the complement system
- Results in inflammation and damage to the glomerular basement membrane
- Cellular infiltration:
- Neutrophils and macrophages infiltrate the glomeruli
- Further damage occurs due to release of inflammatory mediators
- Histopathology:
- Light microscopy: Diffuse proliferative glomerulonephritis
- Immunofluorescence: Granular deposits of IgG and C3 along the glomerular capillary walls
- Electron microscopy: Subepithelial "hump-like" deposits
Clinical Presentation of PSGN in Children
The clinical presentation of PSGN can range from asymptomatic to severe, with the classic triad of hematuria, edema, and hypertension.
Common Symptoms and Signs:
- Hematuria:
- Gross hematuria (cola-colored urine) in 30-50% of cases
- Microscopic hematuria in almost all cases
- Edema:
- Periorbital edema is often the first sign
- May progress to generalized edema
- Hypertension:
- Present in 60-80% of cases
- Can be severe, leading to hypertensive encephalopathy in rare cases
- Oliguria: Reduced urine output in some cases
- Constitutional symptoms:
- Fever
- Malaise
- Abdominal or flank pain
- Headache
Less Common Presentations:
- Nephrotic syndrome: In a small percentage of cases
- Rapidly progressive glomerulonephritis: Rare but severe presentation
- Asymptomatic: Detected only through routine urinalysis
Diagnosis of PSGN in Children
Diagnosis is based on clinical presentation, laboratory findings, and evidence of recent streptococcal infection.
Diagnostic Approach:
- Clinical evaluation:
- History of recent streptococcal infection
- Physical examination: Edema, hypertension
- Urinalysis:
- Hematuria (microscopic or gross)
- Proteinuria (usually mild to moderate)
- Red blood cell casts
- Blood tests:
- Elevated creatinine and BUN (indicating reduced renal function)
- Low C3 complement levels (in 90-95% of cases)
- Normal C4 complement levels
- Elevated anti-streptolysin O (ASO) titer or anti-DNase B antibodies
- Throat or skin culture: May be positive for group A streptococci
- Imaging:
- Renal ultrasound: To assess kidney size and exclude other causes
- Renal biopsy:
- Usually not necessary for typical cases
- May be considered in atypical presentations or prolonged course
Differential Diagnosis:
- IgA nephropathy
- Membranoproliferative glomerulonephritis
- Lupus nephritis
- Henoch-Schönlein purpura nephritis
- Other postinfectious glomerulonephritides
Management of PSGN in Children
Management is primarily supportive, as the condition is usually self-limiting in children.
Treatment Approach:
- Antibiotic therapy:
- Penicillin or erythromycin to eradicate streptococcal infection if still present
- Does not alter the course of glomerulonephritis but prevents spread
- Fluid and electrolyte management:
- Fluid restriction in cases of oliguria or edema
- Sodium restriction (<2 g/day)
- Blood pressure control:
- Antihypertensive medications if needed (e.g., calcium channel blockers, ACE inhibitors)
- Target BP <95th percentile for age, sex, and height
- Management of acute complications:
- Diuretics for severe edema or pulmonary edema
- Dialysis in rare cases of severe acute kidney injury or hyperkalemia
- Monitoring:
- Regular assessment of blood pressure, fluid status, and renal function
- Serial urinalysis to track resolution of hematuria and proteinuria
Patient Education:
- Explain the self-limiting nature of the disease to parents and children
- Emphasize the importance of follow-up and adherence to treatment
- Discuss the need for long-term monitoring
Prognosis and Long-term Outcomes of PSGN in Children
The prognosis for children with PSGN is generally excellent, with most cases resolving without long-term sequelae.
Short-term Outcomes:
- Resolution of acute symptoms:
- Edema typically resolves within 5-10 days
- Hypertension usually normalizes within 2-3 weeks
- Normalization of laboratory values:
- C3 levels return to normal within 6-8 weeks
- Urinary abnormalities may persist for several months
- Recovery of renal function: Usually complete in children
Long-term Prognosis:
- Complete recovery: In >95% of pediatric cases
- Persistent urinary abnormalities: May be present in a small percentage of cases for up to 10 years
- Risk of chronic kidney disease: Very low in children (<1%)
- Recurrence: Extremely rare
Factors Influencing Prognosis:
- Age: Children generally have better outcomes than adults
- Severity of initial presentation
- Presence of comorbidities
- Timely diagnosis and appropriate management
Follow-up Recommendations:
- Regular urinalysis and blood pressure checks for at least 6-12 months
- Annual check-ups to monitor for any long-term renal sequelae
- Counseling on the importance of early treatment of streptococcal infections
Acute Poststreptococcal Glomerulonephritis (PSGN) in Children
- What is the causative agent of Acute Poststreptococcal Glomerulonephritis? Group A beta-hemolytic streptococcus
- What is the typical time interval between streptococcal infection and onset of PSGN? 1-3 weeks
- Which age group is most commonly affected by PSGN? 5-12 years old
- What are the three classic symptoms of PSGN? Hematuria, edema, and hypertension
- What color is the urine typically described as in PSGN? Cola-colored or tea-colored
- Which streptococcal antigen is most commonly implicated in the pathogenesis of PSGN? Nephritis-associated plasmin receptor (NAPlr)
- What is the mechanism of kidney injury in PSGN? Immune complex deposition in glomeruli
- Which complement component is typically decreased in acute PSGN? C3
- What is the gold standard for diagnosing a recent streptococcal infection? Anti-streptolysin O (ASO) titer
- What is the typical pattern of proteinuria in PSGN? Mild to moderate, usually <3 g/day
- How is the diagnosis of PSGN typically made? Clinical presentation and laboratory findings
- What is the role of kidney biopsy in PSGN diagnosis? Usually not necessary, reserved for atypical cases
- What is the characteristic finding on light microscopy in PSGN? Diffuse proliferative glomerulonephritis
- What is the "starry sky" appearance on immunofluorescence in PSGN? Granular deposits of IgG and C3
- What percentage of children with PSGN develop acute kidney injury? About 5%
- What is the primary treatment for uncomplicated PSGN? Supportive care
- When is antibiotic treatment indicated in PSGN? If active streptococcal infection is present
- Which antibiotic is commonly used to eradicate streptococcal infection in PSGN? Penicillin
- How is hypertension typically managed in PSGN? Sodium restriction and diuretics
- What is the usual duration of acute symptoms in PSGN? 1-2 weeks
- What percentage of children with PSGN recover complete renal function? 95%
- How long does it typically take for complement levels to normalize in PSGN? 6-8 weeks
- What is the risk of recurrence of PSGN? Very low, less than 1%
- Which extra-renal complication can occur in severe cases of PSGN? Congestive heart failure
- What is the role of corticosteroids in the treatment of PSGN? Generally not recommended, except in severe crescentic cases
- How often should children with PSGN be followed up after the acute phase? Every 3-6 months for at least 2 years
- What long-term complication should be monitored in children who have had PSGN? Hypertension
- Which urinary finding can persist for months to years after PSGN? Microscopic hematuria
- What is the significance of crescents on kidney biopsy in PSGN? Associated with more severe disease and poorer prognosis
- What preventive measure can reduce the incidence of PSGN in endemic areas? Early treatment of streptococcal infections
Further Reading
- StatPearls: Poststreptococcal Glomerulonephritis
- National Kidney Foundation: Poststreptococcal Glomerulonephritis
- UpToDate: Post-streptococcal glomerulonephritis
- New England Journal of Medicine: Acute Postinfectious Glomerulonephritis in the Modern Era
- Kidney International Reports: Post-Streptococcal Glomerulonephritis
