Scarlet Fever: Strep Throat Complication, Antibiotic Treatment, and Prevention Strategies

Cause and Transmission

Scarlet fever is caused by group A Streptococcus (GAS; Streptococcus pyogenes) strains producing erythrogenic toxins (SpeA, SpeB, SpeC). Spread via respiratory droplets, direct contact, fomites.

Classic Symptoms

• Sore throat, fever (≥101°F/38.3°C)
• Strawberry tongue (white coating → red, papillae prominent)
• Sandpaper rash: fine, erythematous, blanching; starts neck/chest/groin → spreads; Pastia's lines (accentuation in flexures).
• Circumoral pallor.
• Desquamation (peeling) on fingertips/toes in convalescence (week 2-3).

Treatment

• Penicillin VK 250 mg PO BID × 10 days (or amoxicillin 50 mg/kg/day ÷ BID).
• Penicillin allergy: Azithromycin, clarithromycin, clindamycin, or cephalexin (if non-anaphylactic allergy).
• Antipyretics, hydration, throat lozenges.
• Contagious until 24 hrs on antibiotics.

Prevention

• No vaccine exists for GAS or scarlet fever.
• Prompt treatment of strep throat prevents scarlet fever and complications (rheumatic fever, post-strep glomerulonephritis, PANDAS).
• Hygiene: handwashing, covering coughs, not sharing utensils/cups.
• Exclude from school/daycare until afebrile and 24 hrs on antibiotics.

Complications (If Untreated)

• Suppurative: peritonsillar abscess, sinusitis, otitis media, cervical adenitis.
• Non-suppurative: acute rheumatic fever (heart, joints, brain), post-strep glomerulonephritis.