Introduction

Scarlet fever is a reaction to erythrogenic toxins produced by Group A haemolytic streptococci (usually Streptococcus pyogenes). It is more common in children aged 2 - 6 years with the peak incidence being at 4 years.

Epidemiology

  • Incidence: 25.00 cases per 100,000 person-years
  • Peak incidence: 1-5 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Pathophysiology

Scarlet fever is spread via the respiratory route by inhaling or ingesting respiratory droplets or by direct contact with nose and throat discharges, (especially during sneezing and coughing).

Clinical features

Scarlet fever has an incubation period of 2-4 days and typically presents with:
  • fever: typically lasts 24 to 48 hours
  • malaise, headache, nausea/vomiting
  • sore throat
  • 'strawberry' tongue
  • rash - fine punctate erythema ('pinhead') which generally appears first on the torso and spares the palms and soles. Children often have a flushed appearance with circumoral pallor. The rash is often more obvious in the flexures. It is often described as having a rough 'sandpaper' texture. Desquamination occurs later in the course of the illness, particularly around the fingers and toes

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Investigations

Diagnosis
  • a throat swab is normally taken but antibiotic treatment should be commenced immediately, rather than waiting for the results

Management

Management
  • oral penicillin V for 10 days
  • patients who have a penicillin allergy should be given azithromycin
  • children can return to school 24 hours after commencing antibiotics
  • scarlet fever is a notifiable disease

Complications

Scarlet fever is usually a mild illness but may be complicated by:
  • otitis media: the most common complication
  • rheumatic fever: typically occurs 20 days after infection
  • acute glomerulonephritis: typically occurs 10 days after infection
  • invasive complications (e.g. bacteraemia, meningitis, necrotizing fasciitis) are rare but may present acutely with life-threatening illness