Diagnosis and Management of Scarlet Fever

Clinical Diagnosis

The American Academy of Pediatrics and the Infectious Diseases Society of America recommend that the combination of diffuse erythematous rash with pharyngeal findings strongly suggests Group A Streptococcus (GAS) pharyngitis with scarlatiniform rash (scarlet fever) 1, 2
The presence of viral features, such as cough, rhinorrhea, conjunctivitis, hoarseness, oral ulcers, and diarrhea, argues against GAS pharyngitis and testing should not be performed if these are present 1, 3
Features supporting GAS pharyngitis include sudden onset of severe sore throat, fever, tender enlarged anterior cervical lymph nodes, absence of cough, headache, nausea, vomiting, palatal petechiae, or beefy red swollen uvula 2, 3

The Centers for Disease Control and Prevention recommend that clinical features alone cannot reliably discriminate between GAS and viral pharyngitis, so microbiological confirmation is mandatory 1, 2
The Infectious Diseases Society of America recommends performing rapid antigen detection test (RADT) and/or throat culture for diagnosis 1
In children and adolescents, negative RADT must be backed up by throat culture (strong, high-quality evidence) 1, 4
In adults, negative RADT alone is sufficient without culture confirmation due to low incidence of GAS and exceptionally low risk of acute rheumatic fever 1, 4

The American Academy of Pediatrics recommends initiating antibiotic therapy for 10 days to eradicate the organism and prevent complications 1, 4
First-line treatment for penicillin non-allergic patients is penicillin or amoxicillin based on narrow spectrum, infrequency of adverse reactions, and modest cost 1, 4
For penicillin-allergic patients, alternative treatments include first-generation cephalosporin, clindamycin, clarithromycin, or azithromycin 1, 4

Untreated or inadequately treated GAS pharyngitis can lead to severe morbidity and mortality, including acute rheumatic fever and post-streptococcal glomerulonephritis 1, 2

Arcanobacterium haemolyticum can cause pharyngitis with scarlatiniform rash, particularly in teenagers and young adults, and should be considered if GAS testing is negative 2