Kawasaki Disease
Pediatrics
Illness script · Pediatrics
Kawasaki Disease
Acute self-limited vasculitis of medium vessels in young children; leading cause of acquired pediatric coronary artery disease in developed countries.
This illness script for Kawasaki Disease covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Peak age 6 months–5 years; rare >8 years
- Asian (especially Japanese) children have highest incidence
- Males affected ~1.5× more than females
- Likely triggered by infectious antigen in genetically susceptible host
- Winter/spring seasonal clustering
02
Presentation
- Fever ≥5 days PLUS ≥4 of 5 criteria (mnemonic: CRASH)
- Conjunctivitis — bilateral, bulbar, nonexudative
- Rash — polymorphous, truncal
- Adenopathy — unilateral cervical lymph node >1.5 cm (least common)
- Strawberry tongue, red cracked lips, oral/pharyngeal erythema
- Hand/foot changes: erythema → edema → periungual desquamation (late)
03
Pathophysiology
- IgA-mediated vasculitis of medium-sized vessels, especially coronary arteries
- Cytokine-driven endothelial inflammation → vessel wall damage
- Untreated: coronary artery aneurysms develop in ~25% of cases
- Aneurysms can thrombose or rupture → MI, sudden death
04
Diagnostics
- Diagnosis is clinical; no single confirmatory test
- Labs show elevated ESR, CRP, WBC, platelets (thrombocytosis peaks week 2–3)
- Echo at diagnosis and 6–8 weeks to assess coronary arteries
- Incomplete Kawasaki: fewer criteria but echo or labs support diagnosis
- Pearl: Echo is the gold standard for coronary artery involvement
05
Management
- IVIG 2 g/kg single infusion within 10 days of fever onset — reduces aneurysm risk
- High-dose aspirin (80–100 mg/kg/day) during acute phase
- Low-dose aspirin (3–5 mg/kg/day) after afebrile for 6–8 weeks
- IVIG-refractory: repeat IVIG or add infliximab/corticosteroids
- Avoid live vaccines for 11 months after IVIG (immunoglobulin interference)
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Scarlet Fever
Scarlet fever has sandpaper rash + positive strep throat culture/rapid strep; responds to antibiotics
Viral Exanthem (e.g., adenovirus)
Viral exanthems have exudative conjunctivitis and pharyngitis; Kawasaki has nonexudative conjunctivitis
Toxic Shock Syndrome
TSS typically older children/adults with identifiable infection source and hypotension/shock
Juvenile Idiopathic Arthritis (systemic)
Systemic JIA has quotidian salmon-colored rash and arthritis persisting >6 weeks without coronary involvement
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.