Core Dermatology Diagnoses / CategoriesInfectious

Scarlet fever

Author: Faculty Reviewer:

Publish date: Posted on
Last updated: October 8, 2021

Keywords #

scarlet fever
group A streptococcus
GAS
streptococcus pyogenes

Diagnosis #

Scarlet fever is a clinical syndrome caused by certain strains of Group A streptococcal (GAS) bacteria that release the streptococcal pyrogenic exotoxin [3]. It is characterized by the presence of a diffuse maculopapular rash in conjunction with exudative pharyngitis [4]. The characteristic rash is seen in patients who develop a delayed hypersensitivity to the exotoxin, though no single toxin has been consistently associated with scarlet fever [4]. The clinical course usually includes fever and sore throat 1-2 days prior to the rash [3]. The disease generally resolves within 10 days with treatment of the underlying streptococcal infection, but the rash may persist for weeks. 

Key Concepts #
  • Scarlet fever is caused by a delayed hypersensitivity reaction to the exotoxin of GAS bacteria.  
  • Suggestive clinical features include a “sandpaper-like” rash that blanches with pressure, as well as strawberry tongue and Pastia’s lines. 
  • The lack of upper respiratory inflammation distinguishes scarlet fever from measles and rubella, which can present with similar rash and desquamation patterns [1].  
  • Scarlet fever is a clinical diagnosis.  
  • No additional treatment is warranted for the rash of scarlet fever beyond standard of care for a streptococcal pharyngitis infection [2].  
Epidemiology #

10% of children who present with streptococcal tonsillopharyngitis are diagnosed with scarlet fever [3]. The syndrome is most common in children aged 3-8 years old [2]. 

Clinical Features #
  • A “sandpaper-like” rash originates in the inguinal and axillary regions. After 7-10 days, the rash often spreads to the extremities and desquamates on palms and soles [1,2].  
  • High fevers, sore throat, anterior cervical lymphadenopathy.   
  • Strawberry-like tongue characterized by erythematous, swollen papillae with white coating [3].  
  • Pastia’s lines, which are petechial linear patches, may develop in skin folds [3].  
  • Flushed cheeks with sparing of the peri-orbital area [4]. 
Differential Diagnoses #
Diagnostic Workup #

Scarlet fever is primarily a clinical diagnosis made through history and physical examination. Prolonged duration of pyrexia, tachycardia, and spreading of the bilateral trunk rash are suggestive features [2]. Tonsillar swab (sensitivity of 90-95%) and the Centor Score system, which awards points based on clinical features of GAS, are options in unclear cases. 

Treatment #

Beta–lactam antibiotics such as penicillin are the preferred treatment for GAS [2]. Children allergic to penicillin and cephalosporins can receive treatment with oral macrolides or clindamycin [3]. If untreated, GAS infections can cause complications, such as acute glomerulonephritis or rheumatic fever. Rheumatic fever can lead to painful and inflamed joints, or heart valve damage, among other things. 

References #
  1. Kang JH. Febrile illness with skin rashes. Infect Chemother. 2015;47(3):155–166.  
  2. Basetti S, Hodgson J, Rawson TM, Majeet A. Scarlet fever: a guide for general practitioners. London J Prim Care (Abingdon). 2017; 9 (5): 77-79.  
  3. Allmon A, Deane K, Martin KL. Common Skin Rashes in Children. Am Fam Physician. 2015; 92(3): 211-216. 
  4. Wessels MR. Pharyngitis and scarlet fever; Streptococcus pyogenes: basic biology to clinical manifestations. Oklahoma (OK): NCBI; 2016. 
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