Paediatrics · Hard
This case is fictional and exists for study. It describes no real patient.
2 years · male
A 2-year-old boy is brought to the emergency department by his parents due to a 6-day history of continuous high fever reaching 39.5°C, unresponsive to antipyretics. Three days ago, he developed a red rash over his trunk and groins. On physical examination, he appears irritable. Clinical findings include marked redness of the lips with superficial cracking, an erythematous 'strawberry' tongue, and bilateral bulbar conjunctival injection without exudate. His hands and feet display firm erythema and non-pitting oedema. A non-tender left cervical lymph node measuring 1.8 cm is palpated. Chest is clear and abdomen is soft.
Vital signs
- HR
- 140 bpm
- BP
- 92/58 mmHg
- RR
- 32/min
- Temp
- 39.2 °C
- SpO₂
- 98%
Examination findings
- Bilateral non-purulent bulbar conjunctival injection
- Erythematous cracked lips and strawberry tongue
- Polymorphous maculopapular rash on trunk and groin
- Erythema and firm non-pitting oedema of palms and soles
- Unilateral anterior cervical lymphadenopathy (1.8 cm)
Investigations
| C-reactive protein (CRP) | 88 mg/L | reference: < 5 |
| Erythrocyte sedimentation rate (ESR) | 65 mm/hr | reference: 0-10 |
| White blood cell count (WBC) | 16.2 10^9/L | reference: 5.0-15.0 |
| Platelet count | 540 10^9/L | reference: 150-450 |
Question 1 of 3
What is the most likely diagnosis?
Kawasaki disease is a clinical diagnosis established by fever lasting 5 or more days plus at least 4 of the 5 key criteria: non-exudative conjunctivitis, oral mucosal changes (cracked lips, strawberry tongue), peripheral extremity changes (erythema/oedema), polymorphous rash, and cervical lymphadenopathy (>1.5 cm). Scarlet fever typically presents with a rough 'sandpaper' rash, exudative tonsillitis, and strawberry tongue, but lacks conjunctivitis or extremity changes. Measles presents with Koplik spots, maculopapular rash spreading from head down, and marked upper respiratory tract symptoms (cough, coryza). Erythema multiforme typically presents with targetoid (bulls-eye) lesions.
Teaching point: Kawasaki disease is diagnosed clinically by high fever for at least 5 days accompanied by 4 out of 5 principal clinical features.
Question 2 of 3
What is the most appropriate next step in management?
The definitive acute management of Kawasaki disease to prevent coronary artery aneurysms is high-dose IVIG (2 g/kg as a single infusion) combined with high-dose oral aspirin. Antibiotics like amoxicillin or ceftriaxone are ineffective because Kawasaki disease is a non-bacterial inflammatory vasculitis. Oral prednisolone monotherapy is not standard first-line treatment and does not replace IVIG.
Teaching point: Prompt administration of high-dose IVIG and high-dose aspirin within 10 days of fever onset reduces the risk of coronary artery aneurysms from 25% to under 5%.
Question 3 of 3
Which investigation is most appropriate to perform urgently to evaluate for cardiac sequelae?
A baseline transthoracic echocardiogram should be performed at diagnosis (and repeated at 6 weeks) to evaluate coronary artery anatomy for ectasia or aneurysm formation, as well as checking left ventricular function and pericardial effusion. An ECG can detect conduction abnormalities or ischaemia, but directly imaging the coronary arteries via echocardiography is the primary diagnostic investigation for cardiac complications. Cardiac MRI and troponin are not initial screening investigations.
Teaching point: Transthoracic echocardiography is the principal imaging modality to assess for coronary artery aneurysms in Kawasaki disease.
Key learning points
- Kawasaki disease is a medium-vessel vasculitis diagnosed clinically with high fever (>= 5 days) plus 4 of 5 principal features: conjunctivitis, mucosal changes, extremity changes, rash, and cervical lymphadenopathy.
- First-line therapy consists of high-dose IVIG and oral aspirin administered within 10 days of onset to prevent coronary artery aneurysm development.
- Transthoracic echocardiography is essential at baseline and follow-up to detect coronary artery ectasia, dilatation, or aneurysm formation.
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