Case studies · Paediatrics · 19 October 2026

Kawasaki disease case study

The case

Patient: A 3‑year‑old boy, previously healthy, presented to the emergency department with a 5‑day history of fever.

Presenting complaint: Persistent high‑grade fever (≥ 39 °C) lasting 5 days, associated with irritability and reduced oral intake.

History of present illness:

• Fever started abruptly, spikes to 39.5 °C every 6–8 h, partially responsive to paracetamol.
• On day 2, parents noticed red eyes without discharge.
• On day 3, a diffuse, non‑pruritic rash appeared on the trunk and extremities.
• On day 4, the child developed swollen, painful hands and feet; the fingertips became erythematous and later desquamated.
• On day 5, the mother observed cracking and redness at the corners of the mouth and a “strawberry” tongue.

Past medical history: Unremarkable; up‑to‑date immunizations. No prior hospitalizations.

Family history: No history of autoimmune disease, vasculitis, or coronary artery disease.

Social history: Lives in an urban area, attends a daycare. No exposure to sick contacts reported.

Examination (Day 5 of illness):

Initial investigations:

Questions

1. What is the most likely diagnosis?
2. Which clinical and laboratory findings support this diagnosis, and why are they important?
3. According to the American Heart Association (AHA) 2017 guidelines, what are the criteria for complete and incomplete Kawasaki disease?
4. Outline the first‑line management for this patient, including drug regimen, dosing, and monitoring.
5. What are the potential cardiac complications, their timeline, and recommended follow‑up imaging?

Answers

1. What is the most likely diagnosis?

Kawasaki disease (KD) – an acute, self‑limited vasculitis of medium‑size arteries, predominantly affecting children < 5 years. The classic presentation includes prolonged fever (≥ 5 days) plus ≥ 4 of the 5 principal clinical features (conjunctival injection, oral mucosal changes, peripheral extremity changes, polymorphous rash, cervical lymphadenopathy). The presence of coronary artery dilatation on echocardiography confirms vascular involvement.

2. Which clinical and laboratory findings support this diagnosis, and why are they important?

These findings collectively satisfy the complete KD criteria (fever + 4/5 principal features) and confirm vascular involvement, guiding urgent therapy to prevent coronary aneurysms.

3. According to the American Heart Association (AHA) 2017 guidelines, what are the criteria for complete and incomplete Kawasaki disease?

Complete KD (AHA 2017):

• Fever ≥ 5 days plus ≥ 4 of the following 5 principal clinical features:
  1. Bilateral non‑exudative conjunctival injection
  2. Oral mucosal changes (erythema, cracked lips, strawberry tongue)
  3. Peripheral extremity changes (erythema of palms/soles, edema, periungual desquamation)
  4. Polymorphous rash (non‑vesicular, non‑purpuric)
  5. Cervical lymphadenopathy (≥ 1.5 cm, usually unilateral)

Incomplete KD (AHA 2017):

• Fever ≥ 5 days plus 2 or 3 principal clinical features and either:
  • Laboratory evidence of systemic inflammation (elevated ESR/CRP, anemia, hypoalbuminemia, elevated ALT, leukocytosis, thrombocytosis after day 7) or
  • Echocardiographic evidence of coronary artery abnormalities (Z‑score ≥ 2.5) or pericardial effusion.

In practice, if a child has prolonged fever and only 2–3 features but shows markedly raised inflammatory markers or coronary changes, treatment for KD should be initiated without waiting for full criteria.

4. Outline the first‑line management for this patient, including drug regimen, dosing, and monitoring.

Goal: Suppress inflammation rapidly to prevent coronary artery aneurysm formation.

Rationale for IVIG: High‑dose IVIG administered within the first 10 days of illness reduces the risk of coronary artery aneurysm from ~25 % to < 5 % (AHA 2017).

Aspirin dosing strategy:

• High‑dose phase (anti‑inflammatory) → 30–50 mg/kg/day until afebrile for 48 h.
• Low‑dose phase (antiplatelet) → 3–5 mg/kg/day (once daily) continued for 6–8 weeks if coronary arteries are normal, or ≥ 12 months if aneurysms persist.

Laboratory monitoring:

• CBC, ESR, CRP on day 0, day 2, and day 7 to assess response.
• Liver function tests (AST/ALT) because high‑dose aspirin can cause hepatotoxicity.
• Renal function (BUN, creatinine) before and after IVIG (risk of volume overload).

Cardiac monitoring:

• Baseline echocardiogram before IVIG (already performed).
• Repeat echo at 2 weeks, 6 weeks, and then at 1 year if coronary abnormalities were present.

5. What are the potential cardiac complications, their timeline, and recommended follow‑up imaging?

Long‑term outlook: Children with Z‑score < 2.5 and no aneurysm have a normal prognosis; low‑dose aspirin is stopped after 6–8 weeks. Those with persistent aneurysms (Z‑score ≥ 2.5) require lifelong cardiology follow‑up, antiplatelet therapy, and possibly anticoagulation (warfarin or low‑molecular‑weight heparin) if aneurysm size > 8 mm.

Key learning points

• Kawasaki disease is the leading cause of acquired coronary artery aneurysms in children; early recognition and treatment are essential.
• Fever ≥ 5 days plus ≥ 4 principal clinical features constitute complete KD; incomplete KD is diagnosed when fever plus 2–3 features are accompanied by strong laboratory or echocardiographic evidence.
• Elevated ESR/CRP, leukocytosis, thrombocytosis (after day 7), and hypoalbuminemia are supportive laboratory clues.
• IVIG 2 g/kg given within the first 10 days dramatically reduces coronary complications; a second dose is considered for IVIG‑resistant cases.
• High‑dose aspirin is used for its anti‑inflammatory effect; transition to low‑dose antiplatelet therapy after the acute phase.
• Coronary artery Z‑scores are the preferred method to quantify dilatation; a Z‑score ≥ 2.5 indicates aneurysm.
• Serial echocardiography at defined intervals (baseline, 2 weeks, 6 weeks, 6 months, 1 year) monitors for evolving cardiac lesions.
• Long‑term management depends on aneurysm size: small/no aneurysm → stop aspirin after 6–8 weeks; medium/large aneurysm → prolonged antiplatelet/anticoagulation and cardiology follow‑up.

Practice MCQs

1. A 2‑year‑old girl presents with 6 days of fever, bilateral conjunctival injection, cracked lips, and a polymorphous rash. Her ESR is 70 mm/h and platelet count is 380 × 10⁹/L. Which of the following is the most appropriate next step?

A. Start oral amoxicillin for presumed scarlet fever
B. Obtain a repeat CBC in 2 weeks
C. Administer IVIG 2 g/kg and high‑dose aspirin
D. Observe for another 48 h before treatment

Answer: C — The child meets criteria for complete KD (fever + 3 principal features) with strong inflammatory markers; early IVIG plus high‑dose aspirin is indicated to prevent coronary aneurysm.

2. Which echocardiographic finding corresponds to a Z‑score of +3.0 for the left anterior descending artery in a 3‑year‑old?

A. Normal coronary dimensions
B. Mild dilation (Z‑score 2.0–2.5)
C. Moderate aneurysm (Z‑score 2.5–5.0)
D. Giant aneurysm (Z‑score > 10)

Answer: C — A Z‑score between 2.5 and 5.0 defines a moderate coronary artery aneurysm according to AHA 2017 criteria.

3. Which of the following laboratory abnormalities is least commonly associated with Kawasaki disease?

A. Hyponatremia
B. Elevated ALT
C. Thrombocytopenia in the acute phase
D. Anemia of chronic disease

Answer: C — Thrombocytosis, not thrombocytopenia, is typical in the subacute phase; platelet counts are usually normal or low early but rise markedly after day 7.

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