What are the diagnosis criteria for subacute Kawasaki disease?

Diagnostic Criteria for Subacute Kawasaki Disease

The diagnosis of subacute Kawasaki disease is primarily based on clinical findings, with particular attention to periungual desquamation in the subacute phase, which is a characteristic feature that occurs after the acute febrile illness has begun to resolve. 1, 2

Classic Diagnostic Criteria

Kawasaki disease diagnosis requires:

1. Fever persisting for at least 5 days (with day of fever onset counted as the first day)
2. At least 4 of the following 5 principal clinical features:
   • Erythema and cracking of lips, strawberry tongue, and/or erythema of oral and pharyngeal mucosa
   • Bilateral bulbar conjunctival injection without exudate
   • Rash: maculopapular, diffuse erythroderma, or erythema multiforme-like
   • Erythema and edema of the hands and feet in acute phase and/or periungual desquamation in subacute phase
   • Cervical lymphadenopathy (≥1.5 cm diameter), usually unilateral

Subacute Phase Specific Findings

In the subacute phase of Kawasaki disease, several distinctive features may be present:

• Periungual desquamation: This is a hallmark finding of the subacute phase, typically beginning 1-2 weeks after fever onset 1
• Resolution of fever (typically within 36 hours after IVIG treatment if administered)
• Thrombocytosis (commonly seen in the second week after fever onset)
• Some of the acute phase symptoms may have already resolved by presentation

Important Diagnostic Considerations

1. Timing of presentation: A careful history may reveal that one or more principal clinical features were present during the illness but resolved by the time of presentation in the subacute phase 1

2. Incomplete Kawasaki disease: Consider this diagnosis in any child with prolonged unexplained fever, fewer than 4 of the principal clinical findings, and compatible laboratory or echocardiographic findings 1, 2

3. Laboratory findings that support diagnosis:

   • Elevated ESR (≥40 mm/hour has 90.5% sensitivity and 66.6% specificity) 3
   • Elevated CRP
   • Leukocytosis with neutrophil predominance
   • Thrombocytosis (particularly in the subacute phase)
   • Hypoalbuminemia
   • Elevated liver enzymes
   • Sterile pyuria

4. Echocardiography: Should be performed at diagnosis to evaluate for coronary artery abnormalities, which if present, confirm the diagnosis even with fewer clinical criteria 2

Diagnostic Flexibility

• In patients with ≥4 principal clinical criteria (particularly when redness and swelling of hands and feet are present), the diagnosis may be made with only 4 days of fever 1
• Experienced clinicians may make the diagnosis with only 3 days of fever in rare instances with a classic clinical presentation 1
• The diagnosis can be made with only 3 clinical features if coronary artery abnormalities are detected on echocardiography 2

Common Pitfalls in Diagnosis

1. Delayed diagnosis: Particularly common in infants under 6 months, who may present with prolonged fever and irritability as the only clinical manifestations 1

2. Misdiagnosis as bacterial lymphadenitis: In some patients, cervical lymphadenopathy may be the most notable initial finding, delaying KD diagnosis 1

3. Incomplete presentation: Has the same risk of coronary artery abnormalities as complete presentation, making it crucial to recognize 2

4. Confusion with other illnesses: Conditions with similar features should be excluded, particularly those with exudative conjunctivitis, exudative pharyngitis, oral ulcerations, splenomegaly, and vesiculobullous or petechial rashes 1

5. Missing the diagnosis in adults: Although rare, KD can occur in adults and may present with incomplete features 4

Early diagnosis and treatment are critical to reduce the risk of coronary artery abnormalities, which can occur in 20-25% of untreated patients but less than 5% of those receiving appropriate treatment 2, 5.