Scarlet fever is a childhood disease that is caused by a reaction to erythrogenic toxin produced by Streptococcus pyogenes (GAS). Scarlet fever is primarily a clinical diagnosis based on fever, pharyngitis, and the classical scarlatiniform rash.
It peaks at 4 years and commonly affects children aged 6 years.
- Pathophysiology
- Infection with GAS carrying bacteriophages that encode pyrogenic exotoxins→ pyrogenic exotoxins (type A, B, and C) act as superantigens → massive, non-specific T-cell activation and cytokine release
- The result is capillary damage and increased vascular permeability
- Signs and symptoms
- Fever lasting 24 – 48 hours
- ‘Strawberry’ tongue
- White stawberry tongue → red strawberry tongue
- Fine punctate erythema (’pinhead’)
- Initially appears on the torso
- Most obvious in the flexures
- Spares the palms and soles
- Rough ‘sandpaper’ texture due to micropapules
- Desquamation later in the course, especially around the fingers and toes
- Circumoral pallor (due to vasoconstriction in the perioral region)
- Malaise
- Nausea
- Vomiting
- Headache
- Investigations
- Throat swab for bacterial culture or rapid antigen detection if diagnosis is uncertain
- Urinalysis and renal function test if glomerulonephritis is suspected
- CRP, ESR, and antistreptolysin O titres if there are signs of post-streptococcal sequelae
- Treatment
- Scarlet fever is a notifiable illness
- PO penicillin V for 10 days
- PO azithromycin if there is a penicillin allergy
- Resume school 24 hours after starting antibiotics
- Complications
- Otitis media (the most common complication)
- Acute glomerulonephritis (occurs 10 days after infection)
- Rheumatic fever (occurs 20 days after infection)
- Bacteraemia
- Meningitis
- Necrotizing fasciitis
