What are the differences between Kawasaki disease and Multisystem Inflammatory Syndrome in Children (MIS-C)?

Differences Between Kawasaki Disease and MIS-C

MIS-C and Kawasaki Disease are distinct inflammatory conditions with overlapping features, but MIS-C presents with broader age range, more prominent gastrointestinal and neurologic symptoms, and higher rates of shock and cardiac dysfunction compared to Kawasaki Disease. 1

Epidemiological Differences

• MIS-C shows increased incidence in patients of African, Afro-Caribbean, and Hispanic descent, while Kawasaki Disease has higher prevalence in East Asian populations 1
• MIS-C is temporally associated with SARS-CoV-2 infection, typically emerging 2-6 weeks after COVID-19 infection 1
• Kawasaki Disease primarily affects children younger than 5 years, while MIS-C affects a broader age range 1, 2
• Younger children with MIS-C tend to present with KD-like features, while older children more commonly develop myocarditis and shock 1

Clinical Presentation Differences

Feature	Kawasaki Disease	MIS-C
Age	Primarily <5 years	Broader age range [1,2]
Fever	Prolonged (≥5 days)	Present [2]
GI Symptoms	Less common	More prominent (abdominal pain, vomiting, diarrhea) [1,2]
Neurologic Symptoms	Less common	More prominent (headache, altered mental status, encephalopathy) [1]
Shock	Less common	More frequent presentation [1,2]
Cardiac Dysfunction	Primarily coronary artery abnormalities	Higher risk of ventricular dysfunction, arrhythmias, and depressed cardiac output [1,2]
Mucocutaneous Findings	Classic features (conjunctivitis, mucositis, rash, extremity changes)	May have similar features but less consistently [1,2]

Laboratory Differences

• MIS-C typically presents with:
  • Lower platelet counts compared to KD 1
  • Lower absolute lymphocyte counts (lymphopenia) 1, 2
  • Higher C-reactive protein levels 1
  • Elevated troponin levels 2
  • Elevated B-type natriuretic peptide (BNP) 2

Cardiac Manifestations

• Both conditions can lead to coronary artery aneurysms (CAAs) 1
• MIS-C patients are at higher risk for:
  • Ventricular dysfunction 1, 3
  • Arrhythmias 1
  • Depressed cardiac output 2
• MIS-C patients can develop CAAs even without classic KD features 1
• Recent evidence suggests patients with confirmed SARS-CoV-2 infection have higher prevalence of left ventricular dysfunction but potentially less severe coronary artery abnormalities compared to those without evidence of infection 3

Treatment Approaches

• Both conditions are treated with intravenous immune globulin (IVIG) 2
• Aspirin is used in both conditions:
  • In KD: Initially at anti-inflammatory doses, then low-dose for thrombosis prevention
  • In MIS-C: Low-dose for thrombosis prevention 2
• MIS-C management requires:
  • Multidisciplinary team approach including pediatric rheumatologists, cardiologists, infectious disease specialists, and hematologists 1
  • More intensive cardiac monitoring with serial EKGs (every 48 hours) 1
  • Serial echocardiograms at diagnosis, 7-14 days, and 4-6 weeks after presentation 1
  • Trending of cardiac biomarkers (BNP, troponin) until normalization 1

Clinical Pitfalls and Caveats

• Patients presenting with features of either condition should be promptly evaluated and admitted if showing:
  • Abnormal vital signs (tachycardia, tachypnea)
  • Respiratory distress
  • Neurologic changes
  • Renal or hepatic injury
  • Marked inflammation (CRP >10 mg/dl)
  • Abnormal cardiac findings 1
• Both conditions require careful differential diagnosis as symptoms overlap with other infectious and inflammatory conditions 1
• Diagnostic evaluation should include investigation for alternative causes of symptoms 1
• The diagnosis of MIS-C requires evidence of recent or current SARS-CoV-2 infection or exposure 1