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Scarlet Fever
John C. Huscher, MD
image BASICS
  • A disease (typically in childhood) characterized by fever, pharyngitis, and rash caused by group A &bgr;-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
  • 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
  • Increased rates are noted in United Kingdom in 2013.
  • 5-30% of cases of pharyngitis in children are due to GAS.
  • <10% of children with streptococcal pharyngitis develop scarlet fever.
  • 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).
  • 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)
  • 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.
  • Pharyngitis
  • Impetigo
  • Rheumatic fever
  • Glomerulonephritis
  • Oral exam
    • Beefy red tonsils and pharynx with/without exudate
    • Petechiae on palate
    • White coating on tongue: White strawberry tongue appears on days 1 to 2. This sheds by days 4 to 5, leaving a red strawberry tongue, which is shiny and erythematous with prominent papillae.
  • Exanthem (appears within 1 to 5 days)
    • Scarlet macules with generalized erythema; blanches when pressed
    • Orange-red punctate skin eruption with sandpaperlike texture, “sunburn with goose pimples”
    • Coarse “sandpaper” rash—helpful in darkskinned individuals
    • Initially, rash appears on chest and axillae. It then spreads to abdomen and extremities; prominent in skin folds, flexural surfaces (e.g., axillae, groin, buttocks), with sparing of palms and soles.
    • Flushed face with circumoral pallor, red lips
    • Pastia lines: transverse red streaks in skin folds of abdomen, antecubital space, and axillae
    • Desquamation begins on face after 7 to 10 days and proceeds over trunk to hands and feet; may persist for 6 weeks.
    • In severe cases, small vesicular lesions (miliary sudamina) may appear on abdomen, hands, and feet.
  • Viral exanthem: measles; rubella; roseola
  • Infectious mononucleosis
  • Mycoplasma pneumonia
  • Secondary syphilis
  • Toxic shock syndrome
  • Staphylococcal scalded-skin syndrome
  • Kawasaki disease
  • Drug hypersensitivity
  • Severe sunburn
  • Test for GAS pharyngitis by rapid antigen detection test (RADT) and/or culture with pharyngeal swab because clinical features alone do not reliably discriminate between GAS and viral pharyngitis.
  • Testing for GAS pharyngitis is not recommended for patients with symptoms suggesting a viral etiology (e.g., cough, rhinorrhea, hoarseness, oral ulcers).
Initial Tests (lab, imaging)
  • RADT: diagnostic if positive, 95% specific; sensitivity approaches that of culture. Negative RADT should be confirmed by throat culture. Positive RADTs do not require backup culture (1)[C].
  • Throat culture: &bgr;-hemolytic colonies that are catalase negative and sensitive to bacitracin; culture is the gold standard for confirming streptococcal infection (99% specific, 90-97% sensitive; 5-10% of healthy individuals are carriers) (1).
  • Serologic tests (antistreptolysin O titer and streptozyme tests, antihyaluronidase): Confirm recent GAS infection; not helpful or recommended for diagnosis of acute disease.
  • Gram stain: gram-positive cocci in chains
  • CBC may show elevated WBC count (12,000 to 16,000/mm3); eosinophilia later (second week).
  • Follow-up (posttreatment) throat cultures or RADT not routinely recommended
  • Diagnostic testing and empiric treatment of asymptomatic household contacts of patients with acute streptococcal pharyngitis is not routinely recommended (2)[B].
  • Appropriately symptomatic patients >3 years old with a family member recently diagnosed with laboratory-confirmed GAS pharyngitis may be treated without screening or confirmatory testing (3)[C].
Follow-Up Tests & Special Considerations
  • Recent antibiotic therapy may impact culture results.
  • Within 5 days of symptoms, antibiotics can delay/abolish antistreptolysin O response.
Test Interpretation
Skin lesions reveal characteristic inflammatory reaction, specifically hyperemia, edema, and polymorphonuclear cell infiltration.
Supportive care; analgesic/antipyretic such as acetaminophen or an NSAID, for treatment of moderate to severe symptoms or control of fever

First Line
The main reason for treating GAS is to decrease the risk of acute rheumatic fever. Early treatment decreases duration of symptoms by 1 to 2 days and decreases the period of contagiousness (3)[B].
  • Penicillin (PO; penicillin V and others) for 10 days
    • 250 mg PO BID or TID for ≥27 kg (60 lb); 500 mg BID or TID for >27 kg (60 lb) adolescents and adults(1,4,5)[A]
    • If compliance is questionable, use penicillin G, benzathine: single IM dose 600,000 U for ≥27 kg (60 lb); 1.2 mU for those >27 kg.
  • Amoxicillin (PO) 50 mg/kg once daily or 25 mg/kg twice daily for 10 days (use only for definitive GAS because it can induce rash with some viral infections) (6)[A]
    • Contraindications: penicillin allergy
  • Acetaminophen for fever and pain
  • Precautions: Avoid in patients with penicillin allergy (anaphylaxis).
Second Line
  • For patients allergic to penicillin
    • Azithromycin (Zithromax, Z pack): 12 mg/kg/day (max 500 mg) for 5 days (4)[A]
    • Clarithromycin (Biaxin): children >6 months: 7.5 mg/kg BID for 10 days; adults: 250 mg BID for 10 days
  • Oral cephalosporins: Many are effective, but firstgeneration cephalosporins are less expensive:
    • Cephalexin 25 to 50 mg/kg/day divided every 12 hours for 10 days; max 500 mg every 12 hours (1)[A]
    • Cefadroxil 30 mg/kg/day divided BID; max 500 mg BID for 10 days (1)
  • Clindamycin 20 mg/kg/day divided TID for 10 days (4)[B]
  • Tetracyclines and sulfonamides should not be used.
Peritonsillar abscess; shock symptoms: hypotension, disseminated intravascular coagulation (DIC), cardiac, liver, renal dysfunction
  • Tonsillectomy is recommended with recurrent bouts of pharyngitis (≥6 positive strep cultures in 1 year).
  • While children still may get streptococcal pharyngitis (“strep throat”) after a tonsillectomy, the procedure reduces the frequency and severity of infections.
Follow-up throat culture is not needed unless the patient is symptomatic.
Patient Monitoring
GAS is uniformly susceptible to penicillin, treatment failures are typically due to:
  • Poor adherence to recommended antibiotic therapy
  • &bgr;-Lactamase oral flora hydrolyzing penicillin
  • GAS carrier state and concurrent viral rash (requires no treatment)
  • Repeat exposure to carriers in family: Streptococci persist on nonrinsed toothbrushes and orthodontic appliances for up to 15 days.
  • Recurrent GAS pharyngitis after a recent oral antibiotic course can be retreated with the same agent, an alternative oral agent, or IM penicillin G.
No special diet
  • A brief delay in initiating treatment awaiting culture results does not increase the risk of rheumatic fever.
  • Complete the entire course of antibiotics.
  • Children should not return to school/daycare until they have received >24 hours of antibiotic therapy.
  • Can spread person to person: attend to personal hygiene (wash hands, don't share utensils)
  • “Recurring strep throat: When is tonsillectomy useful?” (http://www.mayoclinic.org/diseasesconditions/strep-throat/expert-answers/recurringstrep-throat/faq-20058360)
  • Symptoms are shortened by 12 to 24 hours with penicillin.
  • Recurrent attacks are possible (different erythrogenic toxins).
1. Choby BA. Diagnosis and treatment of streptococcal pharyngitis. Am Fam Physician. 2009;79(5):383-390.
2. Shulman ST, Bisno AL, Clegg HW, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis: 2012 update by the Infectious Diseases Society of America. Clin Infect Dis. 2012;55(10):1279-1282.
3. University of Michigan Health System. Pharyngitis. Ann Arbor, MI: University of Michigan Health System; 2013. National Guideline Clearinghouse Guideline Summary NGC-9967.
4. Gerber MA, Baltimore RS, Eaton CB, et al. Prevention of rheumatic fever and diagnosis and treatment of acute streptococcal pharyngitis: a scientific statement from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young, the Interdisciplinary Council on Functional Genomics and Translational Biology, and the Interdisciplinary Council on Quality of Care and Outcomes Research: endorsed by the American Academy of Pediatrics.. Circulation. 2009;119(11):1541-1551.
5. van Driel ML, De Sutter AI, Keber N, et al. Different antibiotic treatments for group A streptococcal pharyngitis. Cochrane Database Syst Rev. 2013;(4):CD004406.
6. Lennon DR, Farrell E, Martin DR, et al. Once-daily amoxicillin versus twice-daily penicillin V in group A beta-haemolytic streptococcal pharyngitis. Arch Dis Child. 2008;93(6):474-478.
See Also
  • Pharyngitis
  • Algorithm: Pharyngitis
  • A38.9 Scarlet fever, uncomplicated
  • J02.0 Streptococcal pharyngitis
  • A38.0 Scarlet fever with otitis media
Clinical Pearls
  • Consider scarlet fever in the differential diagnosis of children with fever and an exanthematous rash.
  • Key clinical findings include strawberry tongue, circumoral pallor, and a coarse sandpaper rash.
  • Desquamation (7 to 10 days after symptom onset) may last for several weeks following acute illness in scarlet fever.
  • Throat culture remains the diagnostic test of choice to document streptococcal illness.
  • Penicillin is the drug of choice for treatment.