Infants (<1 year) - Tiny Tempers, Big Trouble
Diagnostic challenge is high as incomplete/atypical presentation is the rule, not the exception. Maintain a high index of suspicion.
- Core Features (Often Incomplete):
- Prolonged, unexplained fever (>5 days) is the most consistent finding.
- Extreme, inconsolable irritability is a hallmark sign.
- Sterile pyuria (WBCs in urine without bacterial growth).
- Key Lab Markers:
- ↑ CRP (>3 mg/dL) and/or ↑ ESR (>40 mm/hr).
- Thrombocytosis (platelets >450,000/μL), typically appears late (after week 1).
- Hypoalbuminemia (<3 g/dL).
⭐ Infants with Kawasaki Disease have the highest risk of developing giant coronary artery aneurysms (CAA), leading to long-term cardiac morbidity.

Toddlers & Children (1-5 yrs) - The Classic CRASH
- This age group typically presents with the classic form of Kawasaki disease: a high-grade fever lasting ≥5 days plus at least four principal clinical features.
📌 Mnemonic: CRASH & Burn (Fever)
- Principal Criteria (≥4 of 5):
- Conjunctivitis: Bilateral, non-purulent, bulbar injection.
- Rash: Polymorphous (maculopapular, morbilliform), non-bullous, often perineal accentuation.
- Adenopathy: Unilateral cervical lymph node >1.5 cm.
- Strawberry tongue & Lip changes: Erythema, fissuring, and cracking of lips.
- Hand & Foot changes: Indurative edema and erythema of palms/soles, followed by periungual desquamation.

- Coronary Artery Aneurysm (CAA) Risk: Lower than in infants, but remains a significant concern. Prompt IVIG is critical.
⭐ Exam Favourite: Prominent, tender, unilateral cervical lymphadenopathy is a very common feature in this age group, sometimes being the most striking sign.
Incomplete vs. Atypical KD - The Diagnostic Dilemma
- Incomplete KD: Classic fever pattern (≥5 days) but with only 2-3 principal clinical criteria. Diagnosis requires high suspicion.
- Atypical KD: Fulfills criteria for KD but presents with unusual, organ-specific findings like renal impairment, facial nerve palsy, or severe arthritis.
The crucial step for suspected Incomplete KD is following the AHA algorithm, triggered by elevated inflammatory markers.
⭐ Infants (<6 months) with unexplained fever for ≥7 days should be evaluated for KD even with no clinical criteria, as they have the highest risk for coronary artery aneurysms.
- Infants <6 months face the highest risk for developing coronary artery aneurysms (CAA).
- Incomplete Kawasaki disease is most frequent in infants, often leading to delayed diagnosis and treatment.
- In young infants, prolonged fever and irritability might be the only presenting signs.
- Older children (>5 years) are more likely to show atypical manifestations like significant arthritis or renal impairment.
- IVIG resistance is notably more common in the infant population.
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