BACTERIAL,  DERMATOLOGY

Scarlet Fever

Pathophysiology

  • Cause: Group A beta-hemolytic streptococcal (GAS) infection, typically Streptococcal Pharyngitis
  • Mechanism: Some GAS strains produce streptococcal pyrogenic exotoxin
  • Susceptibility: Patients with hypersensitivity to the toxin may develop a rash

Epidemiology

  • Occurs in 10% of Streptococcal Pharyngitis cases

Symptoms

  • Fever:
    • Peaks on Day 2
    • Returns to normal on Day 5-7
  • Chills
  • Headache
  • Vomiting
  • Pharyngitis

Signs

  • Facial Appearance:
    • Flushed forehead and cheeks
    • Circumoral pallor
  • Throat:
    • Pharyngitis
    • Hyperemic and edematous tonsils with exudate
    • Inflamed throat covered by a membrane
    • Possible palatal petechiae
  • Tongue:
    • Strawberry tongue
    • Fine papules on tongue surface
    • Dorsum of tongue may have white exudate and projecting edematous papillae
  • Rash:
    • Onset within 12-72 hours after fever
    • Coalescing, blanching erythematous macules (may appear sunburn-like)
    • Fine papular or punctate lesions, with texture like coarse sandpaper
    • Distribution:
      • Starts on the upper trunk
      • Generalizes within 24 hours
      • Affects flexor creases (Pastia lines) in the axillae, groin, and neck (do not blanche)
      • Spares the palms and soles
      • Desquamation (peeling) of palms and soles may occur
  • Desquamation:
    • Follows rash fading after several weeks
    • Affects face, skin folds, hands, and feet
    • May last up to 6 weeks

Labs

  • Streptococcal Rapid Antigen Test
  • Throat Culture:
    • Used to confirm a negative rapid antigen test
  • Antistreptolysin O Titer (ASO Titer):
    • Confirms diagnosis but not typically helpful in acute disease

Differential Diagnosis

  • Staphylococcal Scalded Skin Syndrome
  • Kawasaki Disease:
    • Also with desquamation of palms and soles as well as strawberry tongue

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