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Case 004: Kawasaki Disease with Coronary Artery Aneurysms

Presentation

A 3-year-old boy presents with 7 days of fever, bilateral conjunctival injection, strawberry tongue, cervical lymphadenopathy, and diffuse rash. He has been irritable and refusing to walk.

Vital Signs: - Temperature: 39.5°C - Heart rate: 140 bpm - Blood pressure: 88/52 mmHg - Respiratory rate: 28

Exam: - Conjunctival injection (bilateral, non-purulent) - Cracked red lips, strawberry tongue - Maculopapular truncal rash - Right anterior cervical lymph node 2 cm - Extremity edema with desquamation beginning

Initial Workup

Labs: - WBC: 18,000 (72% neutrophils) - Hemoglobin: 10.2 g/dL - Platelets: 620,000 - ESR: 85 mm/hr - CRP: 14 mg/dL - AST/ALT: 65/58 U/L - Albumin: 2.8 g/dL - Urinalysis: Sterile pyuria

ECG: Sinus tachycardia, normal intervals

Echocardiogram: - LAD: 4.2 mm (Z-score +3.8) - RCA: 3.8 mm (Z-score +3.2) - Normal LV function - Trace pericardial effusion

Clinical Reasoning

Question 1: Does this patient meet criteria for complete Kawasaki disease?

Answer **Yes.** He has fever ≥5 days plus 4 of 5 principal clinical criteria: 1. Bilateral conjunctival injection ✓ 2. Oral mucosal changes ✓ 3. Cervical lymphadenopathy ✓ 4. Polymorphous rash ✓ 5. Extremity changes (edema, desquamation) ✓

Question 2: How do you classify his coronary artery findings?

Answer **Both coronaries meet criteria for small aneurysm:** - LAD Z-score +3.8 = Small aneurysm (Z ≥2.5 to <5) - RCA Z-score +3.2 = Small aneurysm (Z ≥2.5 to <5) Classification per AHA: - No involvement: Z <2.0 - Dilation only: Z 2.0-2.5 - Small aneurysm: Z ≥2.5 to <5 - Medium aneurysm: Z ≥5 to <10 - Giant aneurysm: Z ≥10 or ≥8mm

Question 3: What is his risk stratification?

Answer **High-risk** features present: - Age <6 months: No (age 3 years) - Z-score ≥2.5 at diagnosis: **YES** - Laboratory risk factors: Albumin <3.0 ✓, elevated ALT ✓ Per 2024 AHA guidelines, presence of coronary aneurysm at diagnosis indicates **high-risk** requiring intensified treatment.

Management

Question 4: What is the initial treatment?

Answer **Intensified initial therapy** for high-risk patient: 1. **IVIG 2 g/kg** IV over 10-12 hours 2. **High-dose aspirin** 80-100 mg/kg/day divided q6h (until afebrile 48-72 hours) 3. **Adjunctive corticosteroids** - methylprednisolone 2 mg/kg/day or pulse dose Then transition to: - Low-dose aspirin 3-5 mg/kg/day Given coronary aneurysms, additional anticoagulation may be indicated.

Question 5: After IVIG, patient defervesces but coronary aneurysms persist. What anticoagulation is indicated?

Answer For **small aneurysms (Z 2.5-5):** - Low-dose aspirin 3-5 mg/kg/day alone is typically sufficient - No additional anticoagulation needed unless aneurysms enlarge If aneurysms were **medium (Z 5-10):** - Aspirin PLUS clopidogrel OR - Aspirin PLUS warfarin/LMWH If **giant aneurysms (Z ≥10):** - Aspirin PLUS warfarin (target INR 2.0-3.0) PLUS clopidogrel

Follow-up

At 6-week follow-up, echo shows: - LAD: 3.5 mm (Z-score +2.8) - improved but still dilated - RCA: 3.0 mm (Z-score +2.0) - normalized

Question 6: What is the follow-up plan?

Answer **For persistent small LAD aneurysm:** - Continue low-dose aspirin - Echo at 3 months, 6 months, then per cardiologist - Activity: No contact sports restriction for small aneurysms - Stress testing: Consider at 1 year or if symptoms **Long-term prognosis:** - Small aneurysms often regress within 1-2 years - ~50% of small-medium aneurysms resolve - Giant aneurysms rarely resolve; need lifelong cardiology

Teaching Points

  1. Coronary involvement at diagnosis = high-risk requiring intensified therapy
  2. Z-scores are essential - absolute diameter alone is insufficient
  3. Anticoagulation intensity matches aneurysm size
  4. Most small aneurysms regress but require follow-up
  5. IVIG resistance (persistent fever >36h after IVIG) → second dose IVIG or infliximab