What is the diagnosis and treatment for a patient presenting with a diffuse erythematous rash, white spots at the back of the throat, and a red pharynx?

Diagnosis and Management of Diffuse Erythematous Rash with White Spots at Back of Throat

This presentation is most consistent with scarlet fever (scarlatiniform rash) caused by Group A Streptococcus pharyngitis, and requires microbiological confirmation followed by antibiotic treatment with penicillin or amoxicillin for 10 days to prevent serious complications including acute rheumatic fever and post-streptococcal glomerulonephritis. 1, 2

Clinical Diagnosis

The combination of diffuse erythematous rash with pharyngeal findings strongly suggests Group A Streptococcus (GAS) pharyngitis with scarlatiniform rash (scarlet fever):

• The scarlatiniform rash is caused by streptococcal pyrogenic exotoxins produced by certain strains of GAS, presenting as a diffuse erythematous rash typically on the extremities and trunk 2, 3
• White spots at the back of the throat likely represent tonsillopharyngeal exudates, a characteristic finding in GAS pharyngitis 2, 4
• Red pharynx (tonsillopharyngeal erythema) is a hallmark feature of streptococcal infection 2, 4

Key Distinguishing Features to Assess

Presence of viral features argues AGAINST GAS pharyngitis and testing should not be performed if these are present 1, 5:

• Cough (highly suggestive of viral etiology)
• Rhinorrhea or nasal congestion
• Conjunctivitis
• Hoarseness
• Oral ulcers
• Diarrhea

Features supporting GAS pharyngitis include 2, 4:

• Sudden onset of severe sore throat
• Fever
• Tender enlarged anterior cervical lymph nodes
• Absence of cough
• Headache, nausea, vomiting (especially in children)
• Palatal petechiae or beefy red swollen uvula

Diagnostic Testing Required

Clinical features alone cannot reliably discriminate between GAS and viral pharyngitis, so microbiological confirmation is mandatory 1, 2:

• Perform rapid antigen detection test (RADT) and/or throat culture 1
• In children and adolescents: negative RADT must be backed up by throat culture (strong, high-quality evidence) 1
• 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
• Positive RADT does not require back-up culture because of high specificity 1

Treatment Protocol

If GAS Confirmed by Testing

Initiate antibiotic therapy for 10 days to eradicate the organism and prevent complications 1:

First-line treatment (for penicillin non-allergic patients):

• Penicillin or amoxicillin based on narrow spectrum, infrequency of adverse reactions, and modest cost 1
• Duration: 10 days to prevent acute rheumatic fever 5

For penicillin-allergic patients 1:

• First-generation cephalosporin for 10 days (if not anaphylactically sensitive)
• Clindamycin for 10 days
• Clarithromycin for 10 days
• Azithromycin for 5 days

Adjunctive Symptomatic Treatment

Analgesic/antipyretic therapy should be considered for moderate to severe symptoms or high fever 1:

• Acetaminophen or NSAIDs (strong, high-quality evidence)
• Aspirin must be avoided in children (strong, moderate-quality evidence) 1
• Corticosteroids are not recommended (weak, moderate-quality evidence) 1

Critical Complications to Prevent

Untreated or inadequately treated GAS pharyngitis can lead to severe morbidity and mortality 2, 4, 6:

• Acute rheumatic fever (prevented by appropriate antibiotic treatment) 4, 7
• Post-streptococcal glomerulonephritis 4, 6
• Pulmonary-renal syndrome (rare but associated with high mortality) 6

Alternative Diagnosis to Consider

Arcanobacterium haemolyticum (formerly Corynebacterium hemolyticum) can cause pharyngitis with scarlatiniform rash, particularly in teenagers and young adults 2, 3:

• Presents with diffuse erythematous macular rash on extremities and trunk 3
• Predominantly affects ages 11-22 years 3
• Responds to benzathine penicillin G or erythromycin 3
• Rarely recognized in the United States but should be considered if GAS testing is negative 2

Common Pitfalls to Avoid

• Do not rely on clinical impression alone without microbiological confirmation, as this leads to antibiotic overuse 2
• Do not test or treat if viral features are clearly present (cough, rhinorrhea, conjunctivitis, hoarseness) 1, 5
• Do not forget that patients may be GAS carriers experiencing concurrent viral pharyngitis, where the culture is positive but the illness is viral 1, 2
• Do not use antibiotics for viral pharyngitis, as they do not delay recovery or increase risk of complications when appropriately withheld 7