What are the possible causes of a strawberry tongue in a child under 5 years old presenting with fever, rash, and conjunctivitis?

Strawberry Tongue in a Child Under 5 with Fever, Rash, and Conjunctivitis

In a child under 5 presenting with strawberry tongue, fever, rash, and conjunctivitis, Kawasaki disease is the most critical diagnosis to establish immediately, as untreated disease leads to coronary artery aneurysms in 15-25% of cases, but prompt IVIG therapy within 10 days reduces this risk to approximately 5%. 1, 2, 3

Primary Differential Diagnosis

The combination of strawberry tongue, fever, rash, and conjunctivitis creates a narrow differential that requires urgent evaluation:

Kawasaki Disease (Most Critical)

• Classic Kawasaki disease requires fever ≥5 days plus 4 of 5 principal features: bilateral non-purulent conjunctival injection, oral changes (strawberry tongue, cracked lips), polymorphous rash, extremity changes (erythema/edema of hands/feet), and cervical lymphadenopathy ≥1.5 cm. 1, 4
• The strawberry tongue in Kawasaki disease appears with diffuse erythema of oropharyngeal mucosae, prominent fungiform papillae, and is accompanied by erythema, dryness, fissuring, peeling, cracking, and bleeding of the lips. 2
• Critically, pharyngeal exudates and oral ulcerations are NOT typically seen in Kawasaki disease—their presence should prompt consideration of alternative diagnoses. 2
• Incomplete Kawasaki disease is particularly common in infants under 1 year and can present with fewer than 4 principal features, yet carries the same 25% risk of coronary complications if untreated. 1, 4, 5

Scarlet Fever (Key Alternative)

• Scarlet fever presents with high fever, strawberry tongue (initially white-coated, then bright red with prominent papillae), and a characteristic sandpaper-like rash. 2, 4
• The strawberry tongue appearance in scarlet fever is clinically indistinguishable from Kawasaki disease. 2
• Scarlet fever is more common in children aged 5-15 years, making it less likely in children under 5, and typically presents with exudative pharyngitis and sore throat—features that argue against Kawasaki disease. 2, 4
• The absence of pharyngeal exudate favors Kawasaki disease over scarlet fever. 2

MIS-C (Multisystem Inflammatory Syndrome in Children)

• MIS-C presents with overlapping features to Kawasaki disease but typically shows more prominent gastrointestinal symptoms, lower platelet counts, and higher CRP levels than classic Kawasaki disease. 4
• Patients can develop coronary artery aneurysms even without classic Kawasaki disease features. 2

Immediate Diagnostic Algorithm

When a child under 5 presents with fever, strawberry tongue, rash, and conjunctivitis, execute this stepwise approach:

Step 1: Count Kawasaki Disease Principal Features

• Assess all 5 features systematically: bilateral non-purulent conjunctivitis (present), oral changes including strawberry tongue (present), polymorphous rash (present), extremity changes (erythema/edema of hands/feet with sharp demarcation at wrists/ankles), and cervical lymphadenopathy ≥1.5 cm. 1, 4, 5
• Check for perineal involvement and early desquamation in the groin region, which is characteristic of Kawasaki disease. 5
• Look for additional supportive features: irritability, sterile pyuria, and perineal desquamation. 4

Step 2: If Fever ≥5 Days with 2-3 Kawasaki Features

• Immediately measure ESR and CRP. 4
• If ESR ≥40 mm/hr and/or CRP ≥3 mg/dL, obtain: complete blood count with differential, comprehensive metabolic panel (albumin, transaminases), urinalysis, and echocardiography. 4
• Supplemental laboratory criteria supporting Kawasaki disease include: albumin ≤3.0 g/dL, anemia for age, elevated alanine aminotransferase, platelets after 7 days >450,000/mm³, white blood cell count >15,000/mm³, and urine >10 white blood cells/high-power field. 1

Step 3: Obtain SARS-CoV-2 Testing

• Check SARS-CoV-2 PCR and serology to rule out MIS-C in all suspected Kawasaki disease cases. 4

Step 4: Perform Rapid Strep Testing and Throat Culture

• Blood cultures and rapid strep testing help differentiate bacterial causes (scarlet fever) from vasculitic conditions (Kawasaki disease). 2
• Do not dismiss Kawasaki disease if the patient was initially treated with antibiotics for presumed bacterial infection—this is a classic missed diagnosis scenario. 4

Step 5: Echocardiography Interpretation

• Echocardiogram is considered positive if any of these conditions are met: z score of left anterior descending or right coronary artery ≥2.5, coronary arteries meet Japanese Ministry of Health criteria for aneurysms, or ≥3 suggestive features exist (perivascular brightness, lack of tapering, decreased left ventricular function, mitral regurgitation, pericardial effusion, or z scores of 2–2.5). 1

Critical Diagnostic Pitfalls to Avoid

• Do not wait for all 5 Kawasaki criteria in a child under 5 with prolonged fever—incomplete Kawasaki disease is more common in this age group and carries the same risk of coronary complications. 4, 5
• Do not dismiss Kawasaki disease because conjunctivitis is absent—incomplete Kawasaki disease is particularly common in infants <1 year and can present with fewer than 4 principal features. 4
• Young infants (<6 months) with prolonged fever (≥7 days) and systemic inflammation require echocardiography even with minimal clinical features due to high risk of coronary complications. 1, 4
• Do not attribute strawberry tongue and rash solely to antibiotic reaction if the patient was initially treated for presumed bacterial infection. 4

Less Common Causes (Lower Priority in This Clinical Context)

• Candidiasis can cause a bright red tongue after white plaques are removed, but this is more common in immunocompromised patients and would not explain fever, rash, and conjunctivitis. 2
• Other systemic vasculitides can present with bright red tongue as part of multiorgan involvement, but these are rare in children under 5. 2

Management Implications

• Patients with suspected Kawasaki disease require immediate hospitalization for multidisciplinary team involvement, serial cardiac monitoring, and preparation for IVIG therapy (2 g/kg) once diagnosis is confirmed. 4
• Treatment with IVIG within 10 days of fever onset reduces coronary artery abnormality risk from 25% to approximately 5%. 1, 5, 3
• If there is no response to initial IVIG treatment, patients receive a second dose of IVIG with or without corticosteroids or other adjunctive treatments. 3