What's the next evaluation step for a 4-year-old with fever, runny nose, cough, bilateral conjunctivitis, dry oral mucosa, maculopapular rash, edema and erythema of palms and soles, and a nontender enlarged cervical lymph node?

Echocardiography to Assess for Coronary Artery Abnormalities

This child meets criteria for Kawasaki disease and requires immediate echocardiography to evaluate for coronary artery involvement, followed by urgent treatment with intravenous immunoglobulin (IVIG) 2 g/kg and high-dose aspirin. 1, 2

Why This is Kawasaki Disease

This 4-year-old meets classic diagnostic criteria for Kawasaki disease with:

• Fever for ≥5 days (1 week) 1, 2
• Five of five principal clinical features:
  • Bilateral nonexudative conjunctivitis 1, 2
  • Oral mucosal changes (dry oral mucosa) 1, 2
  • Extremity changes (edema and erythema of palms and soles) 1, 2
  • Polymorphous rash (maculopapular rash) 1, 2
  • Cervical lymphadenopathy (enlarged nontender cervical node) 1, 2

The concurrent upper respiratory symptoms (runny nose, cough) do not exclude Kawasaki disease, as these can coexist with the vasculitis. 1

Immediate Next Steps

1. Echocardiography (Urgent)

• Transthoracic echocardiography is the diagnostic imaging modality of choice to screen for coronary artery aneurysms, ectasia, perivascular brightness, decreased LV function, mitral regurgitation, or pericardial effusion. 1, 3
• Coronary artery abnormalities can be detected even before day 10 of illness, manifesting as coronary arteritis, perivascular brightness, or lack of tapering before frank aneurysm formation. 1
• The echocardiogram should assess z-scores of the left anterior descending (LAD) and right coronary artery (RCA), with z-score ≥2.5 considered abnormal. 1

2. Laboratory Evaluation (Concurrent with Echo)

• Complete blood count (CBC) to assess for leukocytosis, anemia, and thrombocytosis (platelets may be normal early but rise after day 7). 1, 2
• Inflammatory markers: ESR and CRP (typically markedly elevated). 1, 2
• Comprehensive metabolic panel (CMP) including albumin (often <3.0 g/dL), transaminases (may be elevated), and sodium (may be <135 mmol/L). 1
• Urinalysis to assess for sterile pyuria (≥10 WBC/hpf), which is common in Kawasaki disease. 1, 2
• Cardiac biomarkers: BNP or NT-proBNP and troponin T to assess for myocardial involvement. 1, 4
• Electrocardiogram (EKG) to evaluate for conduction abnormalities or other cardiac changes. 1

3. Consider MIS-C in the Differential

While this presentation is classic for Kawasaki disease, multisystem inflammatory syndrome in children (MIS-C) must be considered given overlapping features. 1, 4

• Obtain SARS-CoV-2 PCR and serology to assess for epidemiologic link to COVID-19 (positive test, preceding COVID-like illness, or close contact within past 4 weeks). 1, 4
• MIS-C typically presents with more prominent gastrointestinal symptoms (diarrhea, abdominal pain, vomiting) and shock, though this child's presentation is more consistent with classic Kawasaki disease. 1, 4

Treatment Should Not Be Delayed

If clinical suspicion is high (as in this case with 5/5 criteria), treatment can be initiated before echocardiography results are available. 1, 2

First-Line Treatment:

• IVIG 2 g/kg as a single infusion (reduces coronary artery aneurysm risk from 20-25% to <5% when given within 10 days of fever onset). 1, 5, 3
• High-dose aspirin 80-100 mg/kg/day divided into four doses until fever resolves for 48-72 hours, then transition to low-dose aspirin (3-5 mg/kg/day) as antiplatelet therapy. 1, 5

Critical Pitfalls to Avoid

• Do not dismiss this as a viral illness with antibiotic reaction simply because of the upper respiratory symptoms and rash. This is a common misdiagnosis that delays treatment. 1, 2
• Do not wait for desquamation of fingers and toes, which typically occurs 2-3 weeks after symptom onset during the convalescent phase. 1
• Do not delay treatment waiting for all laboratory results. Treatment within 10 days of fever onset is critical to prevent coronary complications. 1, 5, 3
• Young children (especially <1 year) and those with delayed diagnosis have higher rates of coronary artery abnormalities, making prompt recognition essential. 1, 2, 6

Why Not Other Evaluations First?

• Lumbar puncture is not indicated unless there are specific neurologic concerns beyond irritability, as sterile CSF pleocytosis can occur in Kawasaki disease. 1
• Lymph node biopsy is unnecessary; the nontender cervical lymphadenopathy fits the Kawasaki disease criteria. 1
• Viral PCR panels may be sent but should not delay Kawasaki disease evaluation, as concurrent viral infections do not exclude the diagnosis. 1