What are the diagnostic criteria for Kawasaki disease?

Kawasaki Disease Diagnostic Criteria

Kawasaki disease is diagnosed clinically by the presence of fever for at least 5 days plus at least 4 of 5 principal clinical features: bilateral non-purulent conjunctival injection, oral mucosal changes (cracked lips, strawberry tongue, or diffuse oral erythema), polymorphous rash, extremity changes (erythema/edema of hands/feet or periungual desquamation), and cervical lymphadenopathy ≥1.5 cm. 1, 2, 3

Classic (Complete) Kawasaki Disease

The diagnosis requires:

Fever:

• Temperature >39°C (102.2°F), typically 39-40°C
• Duration ≥5 days (day 1 = first calendar day of fever)
• High spiking and remittent pattern
• Lasts 1-3 weeks if untreated 1, 2, 3

PLUS at least 4 of the following 5 principal features:

1. Bilateral conjunctival injection

   • Non-purulent, painless
   • Bulbar conjunctiva primarily affected
   • Limbus typically spared
   • No photophobia or eye pain 1, 2

2. Oral mucosal changes

   • Erythema and cracking of lips
   • Strawberry tongue
   • Diffuse injection of oral and pharyngeal mucosa
   • No ulcerations, exudates, or focal lesions 1, 2, 3

3. Extremity changes

   • Acute phase: Erythema and edema of hands/feet with sharp demarcation at wrists/ankles; may be painful
   • Convalescent phase: Membranous periungual desquamation (2-3 weeks after fever onset)
   • Beau's lines (transverse nail grooves) at 1-2 months 2, 3

4. Polymorphous rash

   • Appears within first 5 days of fever
   • Truncal distribution, often with groin accentuation
   • Most commonly maculopapular, but may be scarlatiniform, erythema multiforme-like, or urticarial
   • NOT bullous, vesicular, or petechial 1, 3

5. Cervical lymphadenopathy

   • ≥1.5 cm diameter
   • Usually unilateral
   • Confined to anterior cervical triangle
   • Least common principal feature 1, 2, 3

Important Diagnostic Modifications

Early diagnosis (before day 5): Experienced clinicians can diagnose with 4 days of fever if ≥4 principal features present (especially with hand/foot swelling), or rarely with 3 days of fever in classic presentations 1, 3

Diagnosis with fewer clinical features: Classic KD can be diagnosed with only 3 principal clinical features if coronary artery abnormalities are detected on echocardiography 1

Incomplete (Atypical) Kawasaki Disease

Consider in children with:

• Fever ≥5 days PLUS
• Only 2-3 principal clinical features

Next steps:

• Measure CRP and ESR
• If elevated, obtain: serum albumin, transaminases, CBC, urinalysis
• Perform echocardiography to assess for coronary involvement 1, 4

Critical caveat: Incomplete KD carries at least as high a risk for coronary artery complications as classic disease, particularly in infants and young children 1, 4

Essential Exclusions

Must exclude other diagnoses that can mimic KD features, including:

• Bacterial lymphadenitis (when lymphadenopathy predominates)
• Scarlet fever
• Staphylococcal scalded skin syndrome
• Toxic shock syndrome
• Viral exanthems
• Drug reactions 1, 3

Key Clinical Pearls

• Clinical features do not appear simultaneously - careful history-taking is essential to identify features that may have already resolved 1, 2
• Marked irritability is common and may be a presenting feature 5
• Fever resolution after 7 days does not exclude KD - spontaneous resolution can occur 3
• Infants and young children more commonly present with incomplete forms and are at higher risk for coronary complications 4
• No specific diagnostic laboratory test exists - diagnosis remains clinical 1, 2

Supporting Laboratory Findings (Non-Diagnostic)

While not diagnostic criteria, typical findings include:

• Elevated ESR and CRP
• Leukocytosis with left shift
• Thrombocytosis (subacute phase)
• Hypoalbuminemia
• Sterile pyuria
• Elevated transaminases 2