Kawasaki Disease: Recognize Early, Treat Decisively, Protect the Coronaries
A layered clinical curriculum for pediatric residents: bedside recognition, incomplete-disease reasoning, acute and rescue therapy, coronary risk, KD shock and MAS, MIS-C discrimination, long-term management, branching cases, and board-level assessment.
Educational use only. Apply local pathways, formulary constraints, and pediatric cardiology/rheumatology consultation to patient care. Drug doses require independent verification.
The resident’s clinical core
Recognize
Fever plus evolving mucocutaneous inflammation. Ask whether features occurred earlier; they need not coexist. Infants may show only prolonged fever and irritability.
Risk-stratify
Age <6 months and baseline LAD or RCA Z score ≥2.5 are the clearest multiethnic high-risk features. Japanese IVIG-resistance scores do not transport reliably to North American populations.1
Act
Give IVIG 2 g/kg promptly, pair it with aspirin per institutional protocol, and consider up-front intensification when high-risk features or coronary aneurysm are present.
Complete KD: fever plus the five principal features
With ≥4 principal features, diagnosis can be made at 4 days of fever; an experienced clinician may diagnose at 3 days. Count historical findings.1
| Feature | Typical KD finding | Finding that argues against KD |
|---|---|---|
| Eyes | Bilateral bulbar, nonexudative conjunctival injection | Exudate, unilateral disease |
| Mouth | Red/cracked lips, strawberry tongue, diffuse oral-pharyngeal erythema | Oral ulcers, exudative pharyngitis |
| Rash | Polymorphous; often trunk/perineum/extremities | Vesicular or bullous eruption |
| Extremities | Acute palmar/plantar erythema or edema; later periungual peeling | None is uniquely exclusionary; timing matters |
| Nodes | Cervical, usually unilateral, ≥1.5 cm | Diffuse generalized adenopathy suggests another process |
Incomplete KD: a pathway, not a weaker disease
Six errors residents must prevent
- Waiting for day 5 when ≥4 features are already present on day 4.
- Using a normal first-week echocardiogram to rule out KD.
- Letting a positive viral test end the evaluation; concurrent infection does not exclude KD.
- Calling fever at 12–24 hours after IVIG “resistance”; the AHA definition is ≥36 hours after infusion completion.
- Changing coronary Z-score equations between studies and mistaking a formula change for biological change.
- Stopping risk-based surveillance because a prior giant aneurysm remodeled to a smaller lumen.
Deep dive: physiology and why coronary size can mislead
Acute arteritis can injure the coronary wall, producing dilation and aneurysm. Later luminal “regression” may reflect true remodeling, layered thrombosis, or myointimal proliferation. Thus, a smaller lumen does not necessarily mean a normal vessel. Long-term risk is anchored to both maximal-ever and current coronary status, not the latest diameter alone.1
Deep dive: North American high-risk score
The Son model assigns 1 point each for age <6 months, Asian race, and CRP >13 mg/dL, plus 2 points for initial coronary Z score >2; a score ≥3 predicts greater 8-week CAA risk. It can inform discussion, but the 2024 AHA statement emphasizes age <6 months and baseline LAD/RCA Z ≥2.5 as the most reproducible high-risk signals.17
Diagnostic reasoning lab
Use this structured aid to expose your reasoning. It cannot establish or exclude KD and should never delay consultation or treatment.
Patient inputs
Principal clinical features
Supportive laboratory findings
KD versus common mimics
| Alternative | Clues favoring it | Reason not to stop thinking about KD |
|---|---|---|
| Adenovirus | Exudative pharyngitis/conjunctivitis, prominent respiratory disease | Viral PCR positivity is compatible with coincident KD; use phenotype and course. |
| Scarlet fever/GAS | Sandpaper rash, exudative pharyngitis, microbiologic confirmation, antibiotic response | Persistent inflammation or evolving extremity/conjunctival findings require reassessment. |
| Toxic shock/sepsis | Rapid shock, focal infection, multiorgan failure, positive cultures | KD shock syndrome exists; treat possible sepsis while evaluating KD and cardiac function. |
| Systemic JIA/MAS | Quotidian fever, evanescent salmon rash, arthritis; MAS with cytopenias/high ferritin/low fibrinogen | MAS can complicate KD; falling ESR with rising CRP is a warning pattern. |
| Measles | Cough, coryza, exudative conjunctivitis, Koplik spots, cephalocaudal rash | Use exposure and immunization history; isolate while testing. |
| SJS/drug reaction | Painful erosions, ulcers, targetoid/bullous lesions, drug timing | Ulcerative mucositis and vesicles are not characteristic of KD. |
KD versus MIS-C
MIS-C is now uncommon but remains an important high-acuity mimic. The CDC surveillance definition is not a bedside diagnostic rule; it explicitly requires no more likely alternative diagnosis.4
| Domain | More typical of KD | More typical of MIS-C |
|---|---|---|
| Age | Usually <5 years | Often older child/adolescent |
| Clinical emphasis | Mucocutaneous features; coronary abnormalities | Prominent abdominal pain/vomiting/diarrhea, headache, shock |
| CBC | Thrombocytosis often emerges after day 7 | Thrombocytopenia and lymphopenia are more prominent |
| Cardiac phenotype | Coronary dilation/aneurysm | LV systolic dysfunction, troponin/BNP elevation, effusion, shock |
| SARS-CoV-2 | May be incidental | Recent infection/exposure supports the syndrome, but seropositivity alone is weak in a highly exposed population |
Treatment: standard, intensified, resistant, refractory
Medication reference
| Agent | AHA 2024 regimen | Resident-level safety point | Evidence posture |
|---|---|---|---|
| IVIG | 2 g/kg IV over 8–12 h; slower in shock/myocardial dysfunction | Hemolysis risk rises with cumulative dose, non-O blood type, and obesity; ESR is unreliable after IVIG; defer MMR and varicella vaccines 11 months. | Standard of care |
| Aspirin | 30–50 mg/kg/day divided q6h until afebrile 48–72 h, then 3–5 mg/kg once daily | Do not combine with ibuprofen/NSAIDs that interfere with antiplatelet effect. Acute high/medium dose has not shown better coronary outcomes; follow local protocol. | Standard antiplatelet; dose uncertainty in acute phase |
| Prednisolone | 2 mg/kg/day divided q8h (max 60 mg/day) then oral course/taper after CRP normalizes | RAISE benefit was in Japanese high-risk patients; transportability is limited. | Reasonable intensification |
| Methylprednisolone | 2 mg/kg/day divided q12h (max 60 mg/day), transition to prednisone and taper over 2–4 wk once CRP <1 mg/dL | Pulse 30 mg/kg (max 1 g) is a specialist regimen used in severe shock/MAS, not routine uncomplicated KD. | Reasonable intensification/rescue |
| Infliximab | 10 mg/kg IV over 2 h | KIDCARE: faster defervescence, less retreatment, less anemia, shorter stay than second IVIG; trial was underpowered for coronary outcomes. | Supported option for IVIG resistance |
| Anakinra | 10 mg/kg/day IV or SC; inpatient IV often divided q12h; short discharge wean | Safety/pharmacokinetic data exceed efficacy data for coronary outcomes. | Refractory/MAS specialist option |
| Cyclosporine | 5 mg/kg/day PO divided q12h; monitor 2-h level (goal 300–600 ng/mL) and magnesium | Use formulation with reliable absorption; major interaction burden. | Refractory specialist option |
| Cyclophosphamide | 10 mg/kg/day IV in 1–2 doses | Rare rescue for progressive giant aneurysm despite other therapy; hydration and rheumatology consultation. | Exceptional rescue |
KD shock syndrome
- Hypotension, poor perfusion, or myocardial dysfunction; consider ≥20% systolic BP decline from expected baseline.
- Evaluate and empirically cover sepsis until excluded.
- Obtain ECG, troponin/BNP, urgent echo, lactate, and organ-function studies.
- Use fluids judiciously; myocarditis/capillary leak may make indiscriminate boluses harmful.
- Use slower IVIG infusion, PICU monitoring, vasoactive/respiratory support, and up-front anti-inflammatory intensification.
Macrophage activation syndrome
- Suspect with instability, IVIG nonresponse, cytopenias, hepatosplenomegaly, encephalopathy, or multiorgan failure.
- Send ferritin, triglycerides, fibrinogen, CBC, LFTs, LDH, coagulation studies.
- High ferritin, low fibrinogen, transaminitis, coagulopathy, and a falling ESR despite rising CRP are key warnings.
- Escalate immediately to rheumatology/hematology/PICU; corticosteroids and/or anakinra are commonly used.
Discharge safety
- Afebrile ≥36 hours after treatment, clinically stable, with a clear plan for recurrent fever.
- If CAA is present, demonstrate stable dimensions on serial studies or improvement before discharge; follow-up within 1 week.
- Continue antiplatelet therapy exactly as prescribed; provide bleeding and influenza/varicella counseling.
- Defer measles-mumps-rubella and varicella vaccination for 11 months after IVIG unless an outbreak/exposure changes the risk calculation.
- For giant aneurysm, teach myocardial ischemia symptoms and CPR; schedule frequent early echocardiography.
Coronary imaging, Z scores, thromboprophylaxis, and follow-up
AHA coronary classification
| Category | Z score / absolute size | Core implication |
|---|---|---|
| No involvement | Always <2 | Short-term aspirin and follow-up; may discharge from cardiology if serial studies remain normal. |
| Dilation only | 2 to <2.5 | Repeat imaging; aspirin until normalization. |
| Small aneurysm | ≥2.5 to <5 | Longer aspirin and surveillance; adverse-event risk is low when small and regressed. |
| Medium aneurysm | ≥5 to <10 and absolute diameter <8 mm | Consider dual antiplatelet therapy while persistent; periodic ischemia/anatomic assessment. |
| Large/giant aneurysm | ≥10 or absolute diameter ≥8 mm | Aspirin plus systemic anticoagulation; intensive lifelong surveillance. |
Risk-level lookup
Select the maximal-ever coronary category and current status. The output summarizes the AHA 2024 table; cardiology owns the individualized plan.
Acute imaging cadence
- Baseline: echo at diagnosis, but never delay IVIG to obtain it.
- High risk, IVIG resistance, or CAA: repeat during hospitalization; with Z ≥2.5, at least twice weekly until dimensions stabilize.
- No coronary involvement: repeat at 1–2 weeks after discharge. If diagnosis and 1–2-week studies are normal and inflammation resolves, later new clinically important CAA is very unlikely; 4–6-week imaging may be omitted in selected patients under the 2024 approach.
- Recurrent fever after discharge: urgent reassessment and echocardiogram unless a clear alternative diagnosis exists.
Thromboprophylaxis logic
The major 2024 change: anticoagulation may still be considered when a formerly giant aneurysm has regressed to medium (risk 5.2), especially when lumen reduction could represent thrombosis.18
For AHA risk levels 4 and 5, β-blocker and statin therapy may be considered case by case; these are not automatic resident-level prescriptions.
Deep dive: advanced imaging and inducible ischemia
Coronary CTA offers high-resolution anatomy and can establish a baseline in aneurysm patients; CMR adds ventricular function and stress perfusion without ionizing radiation. Exercise stress echocardiography is preferable for routine surveillance when feasible. Invasive angiography is reserved for ischemia, intervention planning, or inadequate noninvasive definition. Surveillance frequency scales with maximal and current CAA severity.
Deep dive: the acute myocardial infarction problem
Children with giant CAA may present with chest/abdominal pain, dyspnea, pallor, vomiting, unexplained distress, arrhythmia, or arrest. Obtain immediate ECG and troponin and activate pediatric cardiology/interventional expertise. Reperfusion strategy depends on STEMI versus non-ST-elevation ACS, coronary anatomy, thrombus burden, timing, and local PCI/CABG capacity; do not apply an adult protocol mechanically.
Branching clinical cases
Choose one case. Each decision changes the next clinical state; feedback explains both the best move and the attractive error.
ABP-style assessment
Choose the single best answer. Explanations distinguish the correct action from the most plausible distractor.
Print-ready quick sheets
At the bedside
- Count current + historical principal features.
- Check fever day; diagnose complete KD at day 4 with ≥4 features.
- For incomplete phenotype, obtain CBC/diff, CRP, ESR, CMP/ALT, albumin, UA microscopy, ECG, echo.
- Do not let a normal early echo or positive viral test close the case.
- Call cardiology early for infant <6 months, shock/MAS, Z ≥2.5, or diagnostic uncertainty.
- Treat established KD immediately with IVIG 2 g/kg + aspirin.
Incomplete KD thresholds
- CRP ≥3 mg/dL and/or ESR ≥40 mm/h
- Support: ≥3/6 — anemia, platelets ≥450k after day 7, albumin ≤3.0, elevated ALT, WBC ≥15k, sterile pyuria ≥10/hpf
- Echo positive: LAD/RCA Z ≥2.5, aneurysm, or ≥3 suggestive cardiac findings
- Infant <6 months + unexplained fever ≥7 days enters pathway even without principal features
After IVIG
- Start the resistance clock when infusion ends.
- Persistent/recrudescent fever ≥36 h = IVIG resistance.
- Repeat clinical/infectious assessment and echo.
- Second IVIG, infliximab, or corticosteroid are common next options.
- Check hemoglobin before repeat IVIG; significant hemolysis shifts the choice.
- ESR rises after IVIG and is not a response marker.
Emergency flags
- Shock, persistent tachycardia, ventricular dysfunction
- Cytopenias, ferritin elevation, falling fibrinogen
- Rapidly enlarging coronary Z score
- Chest/abdominal pain, pallor, vomiting, dyspnea, arrhythmia in giant CAA
- Recurrent fever within 1 week of discharge
Evidence map and update status
The 2024 AHA scientific statement is the clinical backbone. No later U.S. KD management guideline was identified through August 12, 2026. The May 2026 AHA advisory addresses global collaboration and access, not replacement treatment recommendations. The February 2026 Canadian practice point and current pediatric hospital guidance operationalize the AHA update; where they differ, this curriculum labels local-practice variation rather than silently merging recommendations.
Jone PN, et al. Update on Diagnosis and Management of Kawasaki Disease. Circulation. 2024;150:e481–e500. DOI: 10.1161/CIR.0000000000001295.
Gorelik M, et al. 2021 ACR/VF Guideline for the Management of Kawasaki Disease. Arthritis Care Res. 2022;74:538–548. Used for strength/conditionality of complex treatment recommendations.
Chen A, et al. Kawasaki disease: Practical guidance on diagnosis and management. Posted February 2, 2026. Used for acute-care operational details and severe phenotypes.
Case Definitions and Reporting. Used to prevent misuse of a surveillance construct as a bedside KD exclusion rule.
Clinical Treatment of MIS-C. Updated February 19, 2026.
Harahsheh AS, et al. Importance of Fostering International Collaboration for Optimal Outcomes of Kawasaki Disease Worldwide. JAHA. 2026;15:e050184. Contextual update; not a replacement management guideline.
Son MBF, et al. Risk Model Development and Validation for Prediction of Coronary Artery Aneurysms in Kawasaki Disease. JAHA. 2019;8:e011319.
American College of Cardiology. AHA Scientific Statement Update on Kawasaki Disease. April 28, 2025. Used to cross-check major long-term management changes.