Post-streptococcal glomerulonephritis (E) is the correct answer.
Infectious impetigo, caused by Group A Streptococcus (Streptococcus pyogenes), can lead to post-streptococcal glomerulonephritis as a non-suppurative, immune-mediated complication. 1
Understanding the Complications of Impetigo
Direct Evidence from Guidelines
The IDSA guidelines explicitly state that systemic antimicrobials should be used for infections during outbreaks of poststreptococcal glomerulonephritis to help eliminate nephritogenic strains of S. pyogenes from the community 1. This recommendation directly confirms that impetigo can cause post-streptococcal glomerulonephritis.
Mechanism and Clinical Context
Post-streptococcal glomerulonephritis is an autoimmune, non-suppurative complication that occurs after streptococcal infections of either the throat (pharyngitis) or skin (impetigo) 2, 3. The condition results from:
- Cross-reactivity of antibodies with renal tissue via molecular mimicry
- Immune complex deposition in glomeruli
- Typically occurs 1-3 weeks after the initial streptococcal infection
Renal disease can occur after localized skin infection, specifically streptococcal impetigo 4, making this a well-established complication with significant implications for morbidity.
Why the Other Options Are Incorrect
A) Necrotizing fasciitis - While both conditions can be caused by Group A Streptococcus, necrotizing fasciitis is a separate, invasive soft tissue infection, not a complication arising from impetigo 2, 5.
B) Clostridial myonecrosis - This is gas gangrene caused by Clostridium species, not streptococci. It is an entirely different pathogen and disease process 6.
C) Toxic shock - While streptococcal toxic shock syndrome (STSS) can occur with severe GAS infections, it is associated with invasive disease or severe presentations like necrotizing fasciitis, not typical impetigo 7, 4.
D) Rheumatic valvular disease - Acute rheumatic fever and rheumatic heart disease are non-suppurative complications of streptococcal pharyngitis (throat infections), not skin infections like impetigo 2, 3, 8.
Clinical Significance
The recognition that impetigo can lead to post-streptococcal glomerulonephritis has important treatment implications:
- During outbreaks, systemic antibiotics are recommended specifically to eliminate nephritogenic strains from the community
- This represents a public health intervention to prevent serious renal complications
- The complication can occur even after the skin infection has resolved