Scarlet Fever

Condition

Most common in children aged 5–15. Results when a Group A Streptococcus pyogenes organism produces erythrogenic toxin. Prodromal symptoms prior to the acute exanthem: malaise, sore throat, fever (may include rigors), and vomiting. A throat swab should be taken.

Features of the rash

• Appears 12–48 hours after the start of fever.
• Usually starts below the ears, neck, chest, armpits, and groin, before spreading to the rest of the body over 24 hours.
• Punctate and red — a “boiled lobster” or sunburnt appearance; blanches on pressure.
• Prominent on the neck, axillae, cubital fossa (Pastia lines), groin, and skinfolds; absent or sparse on the face, palms, and soles.
• Circumoral pallor.
• Tongue discolouration — white initially, becoming red and bumpy (“strawberry tongue”).
• Feels like fine sandpaper.
• Lasts about 5 days, with fine desquamation.

Diagnosis

Throat swab; anti-deoxyribonuclease B and antistreptolysin-O titres.

Treatment

• Phenoxymethylpenicillin 500mg twice daily for 10 days, or
• Cephalexin 1g twice daily for 10 days, or
• Azithromycin 500mg daily for 5 days.

Children can return to school 24 hours after starting antibiotics and once feeling well.