Scarlet Fever

Scarlet Fever is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • A disease (typically in childhood) characterized by fever, pharyngitis, and rash caused by group A β-hemolytic Streptococcus pyogenes (GAS) that produces erythrogenic toxin
  • Incubation period: 1 to 7 days
  • Duration of illness: 4 to 10 days
  • Rash usually appears on the second day of illness.
  • Rash first appears on the upper chest and flexural creases and then spreads rapidly all over the body.
  • Rash clears at the end of the 1st week and is followed by several weeks of desquamation.
  • System(s) affected: head, eyes, ears, nose, throat, skin/exocrine
  • Synonym(s): scarlatina

Epidemiology

Incidence
  • In developed countries, 15% of school age children and 4–10% of adults have an episode of GAS pharyngitis each year.
  • Scarlet fever is rare in infancy because of maternal antitoxin antibodies.
  • Predominant age: 6 to 12 years
  • Peak age: 4 to 8 years
  • Predominant sex: male = female
  • Rare in the United States in persons >12 years because of high rates (>80%) of lifelong protective antibodies to erythrogenic toxins

Prevalence
  • 15–30% of cases of pharyngitis in children are due to GAS; 5–15% in adults
  • <10% of children with streptococcal pharyngitis develop scarlet fever.

Etiology and Pathophysiology

  • Erythrogenic toxin production is necessary to develop scarlet fever.
  • Three toxin types: A, B, C
  • Toxins damage capillaries (producing rash) and act as superantigens, stimulating cytokine release.
  • Antibodies to toxins prevent development of rash but do not protect against underlying infection.
  • Primary site of streptococcal infection is usually within the tonsils, but scarlet fever may also occur with infection of skin, surgical wounds, or uterus (puerperal scarlet fever).

Risk Factors

  • Winter/spring seasonal increase
  • More common in school-aged children
  • Contact with infected individual(s)
  • Crowded living conditions (e.g., lower socioeconomic status, barracks, child care, schools)

General Prevention

  • Spread by contact with airborne respiratory droplets
  • Asymptomatic contacts do not require cultures/prophylaxis.
  • Symptomatic contacts may be treated with or without culture.
  • Children should not return to school/daycare until they have received 24 hours of antibiotic therapy.

Commonly Associated Conditions

  • Pharyngitis
  • Impetigo
  • Rheumatic fever
  • Glomerulonephritis

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