Scarlet Fever Differential Diagnoses

Updated: Nov 06, 2020
  • Author: Bahman Sotoodian, MD; Chief Editor: William D James, MD  more...
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Diagnostic Considerations

The overwhelming majority of cases of scarlet fever are caused by group A beta-hemolytic streptococci (GABHS). Other bacteria can cause a pharyngitis and similar rash, such as Staphylococcus aureus, Haemophilus influenzae, Arcanobacterium haemolyticum, and Clostridium species. [21] The differential diagnosis includes other causes of fever accompanied by erythematous eruptions. Recurrent cases of scarlet fever have been reported from reinfection with strains unrelated to Streptococcus pyogenes. [22]

The cutaneous eruption of fifth disease may be confused with that of scarlet fever, but the affected child is usually well and afebrile.

Rubella and rubeola may appear similar, but the presence of conjunctivitis, purulent rhinitis, and cough are helpful clues to the diagnosis of rubeola. In addition, the eruption of rubeola usually begins behind the ears and on the scalp and forehead, not on the torso. Rubella typically begins on the head and face.

Other viral exanthemata, such as those caused by Epstein-Barr virus (infectious mononucleosis), enterovirus, HIV infection, and Streptobacillus moniliformis infection (rat bite fever), may also have to be considered.

Other bacteria-associated syndromes with cutaneous eruptions (eg, toxic shock syndrome, secondary syphilis) may appear similar to scarlet fever, but the presence of vasomotor instability and ischemic necrosis of digits in the former and palmoplantar involvement with positive serology in the latter should suffice to differentiate them from scarlet fever.

Noninfectious diseases that should be considered include Kawasaki disease, acute lupus erythematosus, morbilliform drug eruption, and juvenile rheumatoid arthritis.

Other problems to be considered include the following:

  • Arcanobacterium haemolyticum

  • Atropine toxicity

  • Enteroviral infection and nonspecific viral infection

  • Fifth disease

  • Epstein-Barr virus (infectious mononucleosis)

  • HIV infection

  • Juvenile rheumatoid arthritis

  • Pediatric cellulitis

  • Plant allergic reactions

  • Roseola

  • S moniliformis infection (rat bite fever)

  • Severe sunburn

  • Viral exanthema

  • Guttate psoriasis: Streptococcal infection is known to precipitate guttate psoriasis and may also cause scarlet fever. The 2 are easily distinguished, as the flexural erythema with sandpaperlike texture and petechiae of scarlet fever are very different from the disseminated, round, erythematous lesions with silver scale of guttate psoriasis.

Differential Diagnoses