Scarlet fever

Scarlet fever is a syndrome caused by infection with toxin-producing group A β‑hemolytic streptococci (Streptococcus pyogenes, GAS) and primarily affects children between the ages of five and fifteen. The syndrome occurs in less than 10% of cases of streptococcal tonsillopharyngitis and classically presents with fever, pharyngeal erythema with tonsillar exudates, and a fine, scarlet-colored rash that is most pronounced in the groin, underarm, and elbow creases. After approximately a week, the skin begins to desquamate on the face, trunk, hands, fingers, and toes. Antibiotic treatment with penicillin is recommended, as scarlet fever may progress to severe disease and other complications associated with Streptococcus infection (e.g., rheumatic fever and post‑streptococcal glomerulonephritis). Scarlet fever is caused by various types of erythrogenic scarlet fever toxins, secreted by S. pyogenes and as such, recurrent infection with other types of toxins is possible.

• Peak incidence: 5–15 years (although it may affect individuals of any age) ^[1]
• Generally occurs in association with streptococcal cases of tonsillopharyngitis

Epidemiological data refers to the US, unless otherwise specified.

• Pathogen
  • Group A β‑hemolytic streptococci (Streptococcus pyogenes) produce erythrogenic exotoxin A, B, or C
  • Previous infection does not rule out additional episodes of the disease, as there are several different types of scarlet fever toxin.
• Route of transmission: aerosol

References:^[2]

Incubation period

• 2–5 days ^[1]

Initial phase (acute tonsillitis)

• Fever
• Malaise, headache, chills, and myalgias
• Tonsillopharyngitis
  • Sore throat and difficulty swallowing
  • White coating on the tongue
  • Enlarged cervical lymph nodes
• Gastrointestinal symptoms (possible in young children)
  • Abdominal pain
  • Nausea and vomiting

Exanthem phase

• Rash appears 12–48 hours after the onset of fever. ^[3]

Scarlet‑colored maculopapular exanthem (rash)

• Presentation
  • Fine, erythematous, sandpaper‑like texture
  • Blanches with pressure
  • Nonblanching petechiae are often additionally present
  • May be pruritic
  • Pastia lines
    • A key sign of scarlet fever: linear, petechial appearance
    • Most pronounced in the groin, underarm, and elbow creases (i.e., flexural areas)
• Location
  • Begins on the neck
  • Disseminates to the trunk and extremities
• Duration: ∼ 7 days ^[4]

The characteristic scarlet fever rash is said to resemble goosebumps with a sunburn.

Tonsillopharyngitis

• Pharyngeal erythema, possibly with tonsillar exudates
• Strawberry tongue: bright red tongue color with papillary hyperplasia, which is revealed once the white coating has sloughed off
• Typical red, flushed appearance of the cheeks with perioral pallor

Desquamation phase

• Appears 7–10 days after resolution of rash ^[4]
• Skin desquamation: desquamation of the skin in flakes
• Affects face, trunk, hands, fingers, and toes

Findings like coryza, rhinorrhea, cough, hoarseness, anterior stomatitis, conjunctivitis, and ulcerative lesions are atypical for scarlet fever and warrant further investigation.

Scarlet fever is primarily a clinical diagnosis that should be confirmed with additional testing.

• Pathogen detection
  • Throat culture
  • Rapid antigen detection testing (rapid strep test)
• Blood and urine studies
  • Complete blood cell (CBC) count shows leukocytosis with a left shift and possibly eosinophilia over the course of the disease.
  • Urinalysis and liver function tests may indicate complications of scarlet fever (see “Complications” below).
  • ↑ Inflammatory markers: CRP, ESR
• Other tests
  • During the course of disease: elevated antistreptolysin O (ASO) and anti‑deoxyribonuclease B (ADB) titers
  • Positive tourniquet test (Rumpel-Leede capillary‑fragility test) ^[5]

• Other infectious rashes in childhood
• Drug hypersensitivity reaction
• Chickenpox (varicella)
• Kawasaki disease
• Viral tonsillitis (infectious mononucleosis, herpangina)

The differential diagnoses listed here are not exhaustive.

• Indication: All cases of scarlet fever should be treated with antibiotics, both to prevent complications and to prevent transmission.
• Drug of choice: oral penicillin V
• Alternative antibiotics
  • In patients allergic to penicillin: macrolides
  • In cases of recurrence due to antibiotic resistance: cephalosporins
• After 24 hours of antibiotic treatment, the patient is no longer infectious and may return to daycare or school. ^[1]

The aim of antibiotic treatment is to prevent complications and shorten the period of infectivity.

Scarlet fever is considered one of the nonsuppurative (i.e., non-pus forming) complications of streptococcal tonsillopharyngitis. Other complications of GAS infection may also occur during or following scarlet fever, especially in patients who did not receive antibiotic treatment.

Nonsuppurative

• Poststreptococcal glomerulonephritis
• Acute rheumatic fever (rare)
• Sydenham chorea
• Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) ^[6]
  • Definition: a rare disorder that is characterized by sudden onset or exacerbation of obsessive-compulsive disorder (OCD) and/or a tic disorder following infection with S. pyogenes
  • Pathophysiology
    • Not fully understood
    • Preceding GAS infection results in an abnormal immune response with development of cross-reactive, anti-neuronal antibodies ^[7]
  • Clinical features
    • Abrupt onset or exacerbation of symptoms of OCD and/or a tic disorder
    • Possible additional behavioral changes: enuresis, separation anxiety disorder, regression in learning and handwriting ability
  • Diagnostic criteria ^[8]
    • Presence of OCD and/or a tic disorder
    • Onset during childhood
    • Acute onset and episodic course
    • Temporal association with streptococcal infection
    • Neurological abnormalities during episodes (e.g., motoric hyperactivity, choreiform movements of fingers/toes)
  • Treatment
    • Antibiotic eradication of GAS
    • Cognitive behavioral therapy and pharmacologic treatment for OCD and tic disorder

Suppurative (i.e., pus-forming)

• Cervical lymphadenitis
• Retropharyngeal or peritonsillar abscess
• Otitis media
• Sinusitis
• Mastoiditis

We list the most important complications. The selection is not exhaustive.