Kawasaki Disease
An acute childhood vasculitis causing prolonged fever, rash, and mucous membrane inflammation, which can lead to life-threatening coronary artery aneurysms if untreated.
Emergency Management: Acute myocardial infarction due to aneurysm thrombosis requires immediate transfer to a pediatric cardiac intensive care unit and intervention (thrombolytics, heparin, or cardiac catheterization).
Kawasaki Disease is an acute, self-limited, medium-vessel vasculitis that primarily affects infants and young children. It has a striking predilection for the coronary arteries, making it the leading cause of acquired heart disease in children in developed nations.
Detailed Overview
The condition presents with prolonged fever and characteristic mucocutaneous findings, including a polymorphous rash, oral mucosal changes, nonpurulent conjunctivitis, and cervical lymphadenopathy. If untreated, 25% of patients develop coronary artery aneurysms (CAAs). Prompt administration of Intravenous Immunoglobulin (IVIG) and Aspirin significantly reduces this risk. The diagnosis is entirely clinical, as no specific diagnostic test exists.
Epidemiology & Demographics
Highest incidence is in children of Asian descent, particularly Japanese, with an incidence of >250 per 100,000 children under 5. In the US, the incidence is about 20 per 100,000. 85% of cases occur in children < 5 years old.
Etiological Mechanism
The exact cause remains unknown. It is hypothesized to be an aberrant immunological response to an unidentified infectious trigger (viral or bacterial) in a genetically susceptible child.
Primary Causes
No specific pathogen has been identified, but seasonal peaks (winter and early spring) and community clustering suggest an infectious trigger.
An infectious trigger leads to activation of the innate and adaptive immune systems. Macrophages, T cells, and IgA plasma cells infiltrate the walls of medium-sized arteries, especially the coronaries. The ensuing necrotizing arteritis destroys the internal elastic lamina and media, leading to aneurysm formation. This is followed by a subacute phase of subintimal proliferation, which can cause luminal stenosis or thrombosis.
Diagnostic Criteria & Guidelines
Fever for ≥ 5 days AND at least 4 of the following 5 criteria: 1) Bilateral bulbar conjunctival injection without exudate, 2) Changes in lips and oral cavity (e.g., strawberry tongue), 3) Changes in extremities (e.g., peripheral erythema, edema, or desquamation), 4) Polymorphous rash, 5) Cervical lymphadenopathy (≥ 1.5 cm). Note: Aneurysms on echocardiogram can confirm atypical/incomplete cases.
Intravenous Immunoglobulin (IVIG) 2 g/kg as a single continuous infusion over 10-12 hours, ideally given within the first 10 days of illness. PLUS Aspirin: High dose (80-100 mg/kg/day divided QID) for anti-inflammatory effect until fever resolves for 48h, then low dose (3-5 mg/kg/day) for antiplatelet effect for 6-8 weeks.
Second-Line & Adjunctive Therapy
For IVIG-resistant cases (persistent fever 36h post-IVIG): Second dose of IVIG 2 g/kg, OR Intravenous Methylprednisolone (30 mg/kg for 3 days), OR Infliximab 5 mg/kg IV x 1.
Surgical & Procedural Management
Coronary artery bypass grafting (CABG) using internal mammary arteries for patients with severe ischemic heart disease due to thrombosed aneurysms.
Patient Counseling & Advice
Warn parents about Reye syndrome risk with aspirin use during viral illnesses (specifically influenza or varicella). Explain the necessity of long-term cardiac follow-up if aneurysms develop.
Follow-Up & Monitoring Schedule
Serial echocardiograms: at the time of diagnosis, 1-2 weeks, and 4-6 weeks after treatment. Further follow-up depends on the maximum Z-score of the coronary arteries.
Preventive Strategies
There is no known way to prevent Kawasaki Disease.
Excellent if treated promptly, with <1% mortality. However, if giant aneurysms (Z-score ≥ 10) form, the lifelong risk of thrombosis, myocardial infarction, and sudden death remains significant.