Scarlet Fever – Evidence‑Based Clinical Features and Diagnosis

Clinical Presentation

Fever is present in approximately 89 % of patients with scarlet fever (observed in a broad cohort of confirmed cases). 1
Acute pharyngitis is a core manifestation of scarlet fever, frequently accompanying fever and preceding rash development. [1][2]
“Strawberry” or “raspberry” tongue—erythematous tongue with prominent fungiform papillae—is characteristic of scarlet fever and helps differentiate it from uncomplicated streptococcal pharyngitis. [3][4]
Erythematous oral and pharyngeal mucosae are commonly observed in patients with scarlet fever. [3][4]
Palatal petechiae (“doughnut lesions”) occur in scarlet fever and support the diagnosis when present. [1][2]
Tender anterior cervical lymphadenopathy is a frequent finding in scarlet fever across age groups. [1][2]6
Systemic symptoms in children include headache, nausea, vomiting, and abdominal pain, often accompanying fever and pharyngitis. [1][2]4

The absence of oral ulcerations or pharyngeal exudates favors scarlet fever over viral etiologies and can aid clinical discrimination. [5][4]
Findings that argue against scarlet fever and suggest a viral process: conjunctivitis, coryza (runny nose), cough, hoarseness, diarrhea, discrete ulcerative stomatitis, and viral‑type exanthem patterns. Presence of these signs should lower suspicion for scarlet fever. [1][2][4][7]

Acute rheumatic fever may develop if scarlet fever is not promptly treated. 5
Post‑streptococcal glomerulonephritis is a recognized sequela of untreated infection. 7
Endocarditis can occur as a serious invasive complication of untreated Group A Streptococcus infection presenting as scarlet fever. 4

Rapid antigen detection test (RADT) or throat culture is required for microbiological confirmation of Group A Streptococcus in suspected scarlet fever. 1
A positive RADT is considered diagnostic, whereas a negative RADT in children must be followed by a backup throat culture to exclude infection. 7
Clinical features alone predict the presence of Group A Streptococcus in only 35–50 % of cases, even when classic signs are present, underscoring the need for laboratory testing. 8