Basics
Description
- Scarlet fever or "scarlatina " is a manifestation of infection with Streptococcus pyogenes (group A ²-hemolytic Streptococcus) that is characterized by an erythematous "sandpaper " rash. It results from infection with a strain of S. pyogenes that elaborates streptococcal pyrogenic exotoxin (SPE).
- Typically occurs in the setting of streptococcal pharyngitis but may occur with group A streptococcal skin or wound infections
- Associated SPE A, B, C, and F. SPE A is associated with more virulent disease.
- Similar syndrome may also be seen in infection with certain enterotoxin-producing strains of Staphylococcus aureus, known as staphylococcal scarlet fever.
General Prevention
- Prompt treatment leads to fewer secondary cases of streptococcal disease.
- Some experts recommend chemoprophylaxis with penicillin in children with repeated documented episodes occurring at short intervals.
- Control measures, including hygiene advice and exclusion of infected students for 24 hours while initiating penicillin treatment, were ineffective in a school outbreak.
Epidemiology
- Equal prevalence in boys and girls
- Most common between ages 3 and 15 years, possibly related to the requirement for prior sensitization and toxin-specific immunity
- Little seasonal variation, although some increased prevalence in winter and spring
- Incubation period is 2 " 5 days for strep pharyngitis and may be up to 10 days for strep skin infections.
Incidence
Peak incidence during the first few school years
Prevalence
By age 10 years, 80% of children have developed toxin-specific antibodies.
Pathophysiology
- Susceptible individuals are thought to lack toxin-specific immunity. This is supported by results of the Dick test, in which a small amount of toxin introduced intradermally produces local erythema in susceptible individuals but no reaction in those with toxin-specific immunity.
- Rash and other toxic manifestations of scarlet fever have been attributed to the development of hypersensitivity to the toxin, which requires prior exposure to the toxin.
- Toxin production depends on lysogeny of the infecting Streptococcus by a temperate bacteriophage.
- Histologic examination of affected skin shows dilated blood and lymphatic vessels and engorged capillaries, most prominently around hair follicles.
- Acute, edematous polymorphonuclear inflammatory reaction is seen microscopically within affected tissues.
- Epidermal inflammatory reaction is usually followed by hyperkeratosis, which accounts for scaling during defervescence.
Diagnosis
History
- Sudden onset of fever up to 40.5 °C, sore throat, headache, nausea, vomiting, and toxicity are classic symptoms for group A streptococcal disease.
- Texture of rash (e.g., feels like sandpaper) is more important than appearance.
- Characteristic rash typically occurs 12 " 48 hours after onset of fever.
- Patient may complain of abdominal pain or muscle aches before onset of rash as well as aching in extremities or back.
- There may be close contacts with streptococcal infection.
Physical Exam
- Fine maculopapular (sandpaper texture) rash on erythematous background: usually begins on the trunk and spreads to involve almost the entire body within hours to days. Although the rash seen with scarlet fever is generally fine and sandpaper-like, larger papules and petechiae may be seen.
- Rash may be more easily detected by palpation than visual inspection
- Pastia line: accentuation of erythema in flexor creases (antecubital, axillary, inguinal)
- Circumoral pallor: Area around mouth appears pale in comparison to flushed cheeks.
- Rash blanches with pressure and ultimately desquamates: Desquamation occurs within 7 " 21 days from onset of illness.
- Systemic toxicity: may indicate incorrect diagnosis
- Dorsum of tongue: has white coat early in illness with edematous red papillae. White covering desquamates and reveals swollen, red, and mottled strawberry tongue.
- Other findings:
- Pharynx and tonsils are beefy red and may contain exudate.
- Hemorrhagic spots on interior pillar of tonsils and soft palate
- Large, tender anterior cervical nodes
Diagnostic Tests & Interpretation
Lab
- Rapid streptococcal antigen tests: effective as screening tests; 70 " 90% sensitivity and >95% specificity. Positive rapid tests do not require culture confirmation.
- Throat culture: the gold standard with best sensitivity (>90%) for group A ²-hemolytic streptococci. A culture should be performed when rapid test is negative.
- White blood cell count: usually elevated, although may be elevated in viral pharyngitis as well. Low count would be rare with streptococcal infection.
- Eosinophilia (up to 30%): common in the recovery phase
- Dick test: of historic interest; no longer used clinically
- Pitfalls
- A positive throat culture may be evidence only of carriage in some cases of acute pharyngitis that are actually viral (e.g., Epstein-Barr virus).
- Milder disease is becoming more common and is easier to miss. Rash may involve only the bridge of the nose, face, shoulders, and upper chest. Circumoral pallor and severe exudative pharyngitis are being seen less frequently.
Differential Diagnosis
- Viral exanthems (measles, rubella, erythema infectiosum)
- Drug eruptions
- Staphylococcal scalded skin syndrome
- Toxic epidermal necrolysis
- Toxic shock syndrome (streptococcal or staphylococcal)
- Kawasaki disease
- Uncommon entities:
- Infection with Arcanobacterium hemolyticum
- Mercury poisoning (acrodynia)
- Atropine intoxication
- Boric acid poisoning
- Rifampin overdose
Treatment
General Measures
- Identical to therapy for streptococcal pharyngitis
- Therapy started as late as 9 days after illness onset should be effective in preventing acute rheumatic fever.
- May withhold treatment until throat culture result is available
- Immediate therapy probably shortens symptomatic period.
Medication
Penicillin or amoxicillin remain the drugs of choice to treat streptococcal pharyngitis. Resistance to penicillin has never been documented in the United States.
- Oral penicillin V potassium (10 days)
- Children: 250 mg twice or 3 times daily
- Adolescents: 250 mg 4 times daily or 500 mg twice daily
- Oral amoxicillin (10 days)
- 50/mg/kg once daily (max 1,000 mg/dose)
- Alternate 25 mg/kg/dose (max 500 mg/dose) twice daily
- Intramuscular penicillin G benzathine
- Equally effective as oral penicillin
- Dose: 600,000 U for children <14 kg (<30 lb); 900,000 " 1,200,000 U for children 14 " 27 kg; and 1,200,000 U for children >27 kg and adults
- Ensures compliance (only one dose needed)
- Benzathine/procaine penicillin combinations are less painful.
The following medications are options for penicillin-allergic patients:
- Oral cephalexin (10 days)
- 20 mg/kg/dose twice daily (max 500 mg/dose)
- Oral cefadroxil (10 days)
- 30 mg/kg/dose once daily (max 2 g/dose)
- Oral azithromycin (5 days)
- 12 mg/kg/dose once daily (max 500 mg/dose)
- Oral clarithromycin (10 days)
- 7.5 mg/kg/dose twice daily (max 500 mg/dose)
Tetracyclines and sulfonamides should not be used because of resistance of group A streptococci.
Ongoing Care
- Fever and symptoms usually resolve within 24 " 48 hours of antibiotic treatment.
- Nonsuppurative complications occur after the acute streptococcal infection has resolved.
- Acute rheumatic fever occurs an average of 18 days after untreated infection. Treatment must be initiated within 9 days of onset to prevent this complication
- Acute postinfectious glomerulonephritis occurs an average of 10 days after infection. The risk of glomerulonephritis is not reduced by treatment with antibiotics.
Prognosis
Overall prognosis is excellent.
- Few patients suffer suppurative complications.
- Risk of developing acute rheumatic fever in untreated streptococcal infections is about 3% under epidemic conditions (0.3% in endemic situations).
- Acute postinfectious glomerulonephritis is uncommon. Risk may be as high as 10 " 15% following infections with certain nephritogenic strains.
Complications
- Patients with scarlet fever may experience hyperkeratosis. Peeling of the affected skin may also occur 2 weeks after the acute infection.
- Other complications worth noting may occur following any primary manifestation of group A streptococcal infection and are not specific to scarlet fever.
- Streptococcal toxic shock syndrome is a toxin-mediated complication of streptococcal infection that may be life threatening.
- Suppurative complications of streptococcal pharyngitis include the following:
- Cervical adenitis
- Peritonsillar abscess
- Retropharyngeal abscess
- Sinusitis
- Otitis media
- Mastoiditis
- Meningitis
- Brain abscess
- Thrombosis of intracranial venous sinuses
- Nonsuppurative complications include acute rheumatic fever and postinfectious glomerulonephritis
Additional Reading
- Chiappini E, Regoli M, Bonsignori F, et al. Analysis of different recommendations from international guidelines for the management of acute pharyngitis in adults and children. Clin Ther. 2011;33(1):48 " 58. [View Abstract]
- Lamden KH. An outbreak of scarlet fever in a primary school. Arch Dis Child. 2011;96(4):394 " 397. [View Abstract]
- Luk EY, Lo JY, Li AZ, et al. Scarlet fever epidemic, Hong Kong, 2011. Emerg Infect Dis. 2012;18(10):1658 " 1661. [View Abstract]
- Shaikh N, Swaminathan N, Hooper EG. Accuracy and precision of the signs and symptoms of streptococcal pharyngitis in children: a systematic review. J Pediatr. 2012;160(3):487 " 493.e3. [View Abstract]
- Shulman ST, Bisno ST, 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):e86 " e102. [View Abstract]
Codes
ICD09
- 034.1 Scarlet fever
- 034.0 Streptococcal sore throat
ICD10
- A38.9 Scarlet fever, uncomplicated
- J02.0 Streptococcal pharyngitis
SNOMED
- 30242009 Scarlet fever (disorder)
- 186357007 streptococcal sore throat with scarlatina (disorder)
FAQ
- Q: Should household contacts have throat cultures performed?
- A: Obtain cultures only from symptomatic household contacts.
- Q: Is there any indication for throat culture in asymptomatic individuals (e.g., household contact of infected individual or test of cure in treated individual)?
- A: No. Throat culture of close contacts of highly vulnerable individuals (e.g., those with recurrent rheumatic fever) may be indicated.
- Q: Is culture confirmation of strep infection necessary to make the diagnosis of scarlet fever?
- A: No. Although laboratory evidence of strep infection is supportive, scarlet fever is a clinical diagnosis.
- Q: Should posttreatment throat cultures be performed?
- A: Only in symptomatic individuals and patients at risk for acute rheumatic fever.
- Q: Can scarlet fever occur in the absence of pharyngitis?
- A: Yes. Scarlet fever has been reported after group A streptococcal skin infections
- Q: Can scarlet fever recur?
- A: Yes. There have been documented reports of recurrent scarlet fever.
- Q: Have there been documented child care outbreaks of scarlet fever?
- A: Yes. Outbreaks have been traced to single strains in this setting.
- Q: How soon can children return to school or child care?
- A: When they are afebrile and after at least 24 hours of antibiotic therapy