Definition, Diagnostic Criteria & Classification

Question	Answer
1. Detail the American Heart Association (AHA 2017) diagnostic criteria for Classic Kawasaki Disease (KD).	Diagnosis requires Fever lasting $\ge 5$ days (or fever until the date of IVIG administration if given before day 5), accompanied by at least 4 of the following 5 principal clinical features: 1) Bilateral conjunctival injection: Bulbar, non-exudative, painless, sparing the limbus. 2) Oral mucosal changes: Erythema, cracking of lips, strawberry tongue, diffuse erythema of oral and pharyngeal mucosa (no oral ulcers or exudates). 3) Polymorphous exanthem: Maculopapular, diffuse scarlatiniform, or erythema multiforme-like rash (not vesicular or bullous). 4) Extremity changes: Acute phase: Erythema of palms and soles, firm indurative non-pitting edema of hands and feet; Subacute phase: Convalescent periungual membranous desquamation. 5) Cervical lymphadenopathy: Usually unilateral, $>1.5\text{ cm}$ in diameter, firm, non-fluctuant, non-tender or minimally tender.
2. Define "Incomplete (Atypical) Kawasaki Disease" and describe the AHA diagnostic algorithm.	Diagnosed in a child with prolonged unexplained fever $\ge 5$ days with only 2 or 3 principal clinical criteria (or an infant $<6$ months with fever $\ge 7$ days without clinical features): - Check CRP ($\ge 3.0\text{ mg/dL}$) and/or ESR ($\ge 40\text{ mm/hr}$). - If elevated, evaluate for $\ge 3$ supplemental laboratory criteria: 1) Serum Albumin $\le 3.0\text{ g/dL}$. 2) Anemia for age. 3) Elevation of ALT $> 50\text{ U/L}$. 4) Platelet count $\ge 450,000/\mu\text{L}$ after day 7. 5) Total WBC count $\ge 15,000/\mu\text{L}$. 6) Urine WBC $\ge 10/\text{HPF}$ (sterile pyuria). - If $\ge 3$ lab criteria are met, treat with IVIG and perform echocardiogram. If $<3$ criteria met, perform echocardiogram; if echo is positive for coronary changes, treat immediately.
3. How are Coronary Artery Lesions (CAL) classified using Echocardiographic Z-Scores?	Per AHA guidelines, coronary dimensions are normalized to body surface area using Z-scores (standard deviations from the mean): - No involvement: $Z\text{-score} < 2.0$. - Dilation only: $Z\text{-score } 2.0 \text{ to } < 2.5$. - Small aneurysm: $Z\text{-score } 2.5 \text{ to } < 5.0$. - Medium aneurysm: $Z\text{-score } 5.0 \text{ to } < 10.0$, AND absolute internal lumen diameter $<8\text{ mm}$. - Large or Giant aneurysm: $Z\text{-score} \ge 10.0$, OR absolute internal lumen diameter $\ge 8\text{ mm}$.
4. VIVA TRAP: A 3-month-old infant presents with 8 days of unexplained high fever, irritability, and sterile pyuria, but has NO rash, red eyes, or lymphadenopathy. Could this be Kawasaki Disease?	YES! This is a classic presentation of Incomplete Kawasaki Disease in young infants. Infants $<6$ months have the highest risk of incomplete presentations AND the highest risk of developing giant coronary artery aneurysms and fatal myocardial infarction. AHA guidelines mandate that any infant $<6$ months with fever of $\ge 7$ days' duration without an identified cause must undergo echocardiography and laboratory evaluation for Kawasaki disease, even in the complete absence of classical clinical criteria!
5. VIVA TRAP: Can periungual peeling be used to confirm the diagnosis of acute Kawasaki Disease?	NO. Periungual desquamation is a subacute/convalescent feature that characteristically appears 2 to 3 weeks after fever onset. Waiting for desquamation to occur before initiating IVIG therapy causes the clinician to miss the crucial 10-day primary therapeutic window, leading to catastrophic irreversible coronary artery aneurysm formation!

Pathophysiology & Complications

Question	Answer
6. Describe the vascular histopathology of Kawasaki Disease across its stages.	KD is an acute systemic necrotizing vasculitis targeting predominantly medium-sized muscular arteries, especially coronary arteries: - Stage I (Days 0–9, Acute): Marked neutrophilic endarteritis and periarteritis with microvascular endothelial swelling, perivascular edema, and transmural mononuclear infiltration. - Stage II (Days 10–25, Subacute): Progressive panarteritis with destruction of internal elastic lamina and media by infiltrating macrophages, lymphocytes (CD8+), and plasma cells (IgA-producing). Weakened arterial wall undergoes aneurysmal dilation with mural thrombus formation. - Stage III (Days 26–40, Convalescent): Myofibroblastic proliferation, progressive luminal scarring, intimal thickening, and vascular remodeling leading to stenosis or occlusion. - Stage IV (Years later, Chronic): Scarring, calcification, and fixed obstructive coronary stenoses.
7. What are the major cardiovascular complications of Kawasaki Disease?	1) Coronary Artery Aneurysms (CAA): Occur in $20-25\%$ of untreated children; reduced to $<4-5\%$ with timely IVIG. 2) Acute Myocarditis: Present in $>50-70\%$ during the acute phase; causes tachycardia out of proportion to fever, gallop rhythm, decreased left ventricular ejection fraction, and cardiogenic shock (Kawasaki Disease Shock Syndrome - KDSS). 3) Pericardial Effusion: Usually mild to moderate. 4) Valvulitis: Mitral regurgitation (up to $25\%$) due to papillary muscle ischemia or valvulitis. 5) Coronary Thrombosis & Myocardial Infarction: Chief cause of death, most common within the first year following illness.
8. What is Kawasaki Disease Shock Syndrome (KDSS)?	- Characterized by sustained systolic hypotension ($\ge 20\%$ drop below age-specific norms) or clinical signs of peripheral hypoperfusion during acute KD. - Mechanism: Profound capillary leak, systemic vasculitis with nitric oxide release, and acute myocardial dysfunction. - Significance: KDSS patients have significantly higher rates of IVIG resistance, coronary artery aneurysms, and consumptive coagulopathy compared to non-shock KD patients.
9. What is the Kobayashi Score and its clinical relevance?	- Risk score developed in Japan to predict IVIG resistance and high risk of coronary aneurysms. - Parameters (1 point each unless noted): Sodium $\le 133\text{ mmol/L}$ (2 pts), Days of illness at presentation $\le 4$ days (2 pts), AST $\ge 100\text{ U/L}$ (2 pts), Neutrophils $\ge 80\%$ (2 pts), CRP $\ge 10\text{ mg/dL}$ (1 pt), Age $\le 12$ months (1 pt), Platelets $\le 300,000/\mu\text{L}$ (1 pt). - Score $\ge 5$ indicates high risk of IVIG failure; Japanese trials (RAISE study) showed benefit of upfront IVIG + Corticosteroids in this group (though predictive accuracy is lower in non-Japanese populations).

Guidelines & Management Protocols (AHA 2017 Guidelines)

Question	Answer
10. Detail the primary first-line therapeutic regimen for acute Kawasaki Disease.	1) Intravenous Immunoglobulin (IVIG): - Dose: $2.0\text{ g/kg}$ as a single IV infusion administered over 10 to 12 hours. - Timing: Administer within 10 days of fever onset (and after day 10 if persistent fever or ongoing systemic inflammation/coronary dilation is present). 2) Aspirin (Acetylsalicylic Acid - ASA): - Acute Anti-inflammatory Phase: $30\text{ to } 50\text{ mg/kg/day}$ orally in 4 divided doses (in India/Europe; AHA allows $80-100\text{ mg/kg/day}$) given until the child is afebrile for 48 to 72 hours. - Maintenance Anti-platelet Phase: Transition to $3\text{ to } 5\text{ mg/kg}$ orally once daily; continue for 6 to 8 weeks until repeat echocardiogram confirms normal coronaries and inflammatory markers normalize. Continue indefinitely if coronary aneurysms persist.
11. Define "IVIG-Resistant (Refractory) Kawasaki Disease" and outline its management.	- Definition: Persistent or recrudescent fever $\ge 36\text{ hours}$ and $<7\text{ days}$ after completion of the initial IVIG infusion. - Stepwise Management: 1) Second dose of IVIG: $2.0\text{ g/kg}$ IV over 10-12 hours, OR 2) Pulse Methylprednisolone: $30\text{ mg/kg/day}$ IV over 2 hours once daily for 3 consecutive days, followed by oral prednisolone taper over 2-3 weeks. 3) Infliximab (TNF-$\alpha$ inhibitor): $5\text{ mg/kg}$ IV single dose (proven to induce rapid defervescence and reduce hospital stay). 4) Cyclosporine A or Anakinra: Reserved for severe multi-refractory disease.
12. Outline the antithrombotic management for Giant Coronary Artery Aneurysms ($Z \ge 10$ or diameter $\ge 8$ mm).	Children with giant aneurysms are at catastrophic risk of intraluminal thrombosis and sudden death. AHA guidelines mandate Dual Antithrombotic Therapy: 1) Low-dose Aspirin: $3-5\text{ mg/kg/day}$ (antiplatelet), PLUS 2) Systemic Anticoagulation: - Low Molecular Weight Heparin (Enoxaparin): Target anti-Factor Xa level $0.5\text{ to } 1.0\text{ IU/mL}$, OR - Warfarin: Dose-adjusted to maintain Target INR $2.0\text{ to } 3.0$. - In selected cases, triple therapy (Aspirin + Clopidogrel + Anticoagulation) is utilized under expert supervision.

VIVA TRAPs & Counter-Questions

Question	Answer
13. VIVA TRAP: What is the risk of long-term Aspirin therapy in children, and how is it mitigated?	Reye Syndrome: Administration of aspirin during active Influenza or Varicella infection carries a proven risk of Reye syndrome (acute hepatic encephalopathy, microvesicular fatty liver, high mortality). Mitigation Protocol: 1) All children on maintenance aspirin must receive annual inactivated Influenza vaccination. 2) Ensure age-appropriate Varicella vaccination. 3) If the child is exposed to or develops active chickenpox or influenza while on aspirin, immediately discontinue aspirin and substitute with Clopidogrel ($1\text{ mg/kg/day}$) until the viral illness resolves!
14. VIVA TRAP: When can live attenuated vaccines (MMR, Varicella) be administered after high-dose IVIG therapy?	Administration of high-dose IVIG ($2\text{ g/kg}$) introduces massive titers of passive neutralizing antibodies that interfere with the replication and immunogenicity of live attenuated virus vaccines. - Strict Rule: Live vaccines (Measles, Mumps, Rubella, Varicella) must be delayed for 11 months after receiving IVIG ($2\text{ g/kg}$). - Exception: If measles exposure risk is high during an outbreak, give vaccine and repeat 11 months later.
15. Counter-Question Chain: "Why is Lumbar Puncture often performed in Kawasaki disease, and what does it reveal?"	- Severe irritability in acute KD often mimics bacterial or viral meningitis. - Lumbar puncture in acute KD reveals Aseptic Meningitis with a mononuclear pleocytosis (typically $15-50\text{ cells}/\mu\text{L}$, predominantly lymphocytes/monocytes), normal glucose, and normal to mildly elevated protein with negative Gram stain and cultures. - Finding sterile CSF pleocytosis does NOT rule out Kawasaki disease; it is a recognized manifestation of systemic vasculitis!