Strep pyogenes: Presentation

Strep pyogenes presentation/complications: 

• Presentation:
  • Pharyngitis
  • Skin infections
    • Impetigo
      • “honey/golden-crusted” lesions
    • Erysipelas
      • painful red plaque with raised borders
    • Cellulitis
  • Can cause hematogenous osteomyelitis, necrotizing fasciitis
  • Scarlet fever
    • Caused by pyrogenic exotoxin
    • Blanching, sandpaper-like rash, strawberry tongue, and circumoral pallor in the setting of group A streptococcal pharyngitis
      • Erythrogenic toxin +
  • Toxic shock-like syndrome
    • Caused by pyrogenic exotoxin
    • Caused by a superstimulation of T cells 
    • Necrotizing fasciitis
• Complications
  • Rheumatic fever
    • Usually follows untreated pharyngitis, not skin infections
    • antibodies against M protein or other virulence factors (e.g. streptolysin O) can attack self-tissues
      • Similarity of M protein to self-cells is due to molecular mimicry
        • may help the bacteria avoid detection by immune system
    • Presentation:
      • Migratory polyarthritis 
      • Endocarditis
        • presents as acute development of mitral regurgitation
        • Many years later, chronic lesion can present as mitral stenosis 
  • Poststreptococcal Glomerulonephritis
    • Usually occurs 1-2 weeks after GAS infection (e.g. skin, pharynx)
    • Facial edema, dark cola-colored urine, hematuria
    • Caused by immune complex deposition (Type III Hypersensitivity Reaction) 
    • Strains causing impetigo can induce glomerulonephritis