Multisystem Inflammatory Syndrome

Aka: Multisystem Inflammatory Syndrome, Multisystem Inflammatory Syndrome in Children, MIS-C

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II. Epidemiology

  1. First identified during Spring 2020 with onset of Covid19 pandemic
    1. Incidence as of 2024 in U.S. has significantly decreased (alternative diagnosis is far more likely)
  2. Age
    1. Initially identified in children and unlike Kawasaki Disease (age <11 years) extended to age 21
    2. Age range from 1 week to 21 years (median 7-9 years)
    3. Has since been reported in adults
      1. Morris (2020) MMWR Morb Mortal Wkly Rep 69:1450-56 [PubMed]
      2. https://www.cdc.gov/mmwr/volumes/69/wr/mm6940e1.htm
  3. Gender
    1. Boys represent 60% of cases (similar to Kawasaki Disease)
  4. Race (U.S.)
    1. Hispanic or Latino: 32%
    2. Non-Hispanic Black: 30%

III. Pathophysiology

  1. Systemic inflammatory condition as a complication of COVID-19, and similar to Kawasaki Disease

IV. Indications: Evaluation for MIS-C

  1. Suspected or confirmed COVID-19 within prior 4 weeks AND
  2. Fever >3 days AND
  3. No other apparent explanation AND
  4. Two or more of the following systems involved (or unexplained Fever >5 days)
    1. Gastrointestinal findings (80% of patients, and may differentiate MIS-C from Kawasaki Disease)
      1. Abdominal Pain
      2. Diarrhea
      3. Nausea or Vomiting
    2. Neurologic findings (20% of patients)
      1. Headache
      2. Irritability
      3. Lethargy
      4. Altered Mental Status
      5. Neurologic deficits
    3. Head and Neck Symptoms
      1. Conjunctivitis (40%)
      2. Cough
      3. Congestion
      4. Pharyngitis
      5. Oral Lesions or other oral changes
        1. Red Cracked Lips (23%)
        2. Strawberry Tongue (4.5%)
      6. Cervical Lymphadenopathy (4%)
    4. Swelling of hands or feet
    5. Urethritis
    6. Arthralgias or Arthritis
    7. Dermatologic findings
      1. Polymorphic rash
      2. Scaling or peeling of skin (Exfoliative Dermatitis)

V. Labs

  1. Background
    1. Inflammatory markers are typically higher than in Kawasaki Disease
  2. First-Line - Tier 1 Screening
    1. Complete Blood Count with Platelets and differential
      1. White Blood Cell Count increased (12-22k, mean 17k)
        1. Associated with Left Shift (Neutrophil predominance) and lymphocytopenia
        2. Contrast with only mildly elevated White Blood Cell Counts in Kawasaki Disease
      2. Anemia (Hgb 8.3-10.3 g/dl, mean 9.2 g/dl)
      3. Thrombocytopenia (104-210 k/uL, mean 151 k/uL)
        1. Contrast with Thrombocytosis in Kawasaki Disease
    2. Comprehensive metabolic panel
      1. Electrolytes
      2. Renal Function tests
      3. Liver Function Tests
      4. Serum Albumin
        1. Levels 2.1 to 2.7 g/dl (mean 2.4 g/dl)
        2. Contrast with normal Serum Albumin in Kawasaki Disease
    3. Inflammatory Markers
      1. Erythrocyte Sedimentation Rate
      2. C-Reactive Protein
        1. Levels 16 - 34 mg/dl (mean 22 mg/dl)
    4. Covid19 Test (typically nasopharyngeal PCR)
  3. First-Line - Tier 2 Screening
    1. Indications for Tier 2 tests (from Tier 1 Screening)
      1. C-Reactive Protein or CRP >5 mg/L or Erythrocyte Sedimentation Rate or ESR >40 mm/h AND
      2. At least one of the following
        1. Absolute Lymphocyte Count <1000/ul
        2. Platelet Count <150,000/ul or >450,000/ul
        3. Serum Sodium <135 mmol/L
        4. Absolute Neutrophil Count <1000/ul or >15,000/ul
        5. Hypoalbuminemia (e.g. Serum Albumin <3 g/dl)
    2. Tier 2 Tests
      1. INR and PTT
      2. D-Dimer
        1. Levels 2.1 to 8.2 ng/ml (mean 3.6 ng/ml)
      3. Serum Troponin
        1. Levels 0.008 to 0.294 mcg/L (mean 0.045 mcg/L)
        2. Contrast with typically normal serum Troponin In Kawasaki Disease
      4. NT-BNP
        1. Levels 174 to 10,548 pg/ml (mean 788 pg/ml)
        2. Contrast with typically normal NT-BNP in Kawasaki Disease
      5. Urinalysis (and consider Urine Culture)
      6. Blood Culture
  4. Additional Testing to consider (based on Consultation, risk factors)
    1. Fibrinogen
    2. Factor VIII and Von-Willebrand profile
    3. Antithrombin III
    4. Procalcitonin
    5. Serum Ferritin
      1. Levels 359 to 1280 ng/ml (mean 610 ng/ml)
    6. Serum Triglycerides
    7. Total IgG
    8. Respiratory Viral Panel
    9. Strep Test
    10. Mycoplasma PCR
    11. HIV Test
    12. Tick-Borne Illness Serology (e.g. Lyme Disease, Babesiosis, Anaplasmosis, Rickettsia - depending on region)
    13. Tuberculosis Testing (e.g. IGRA Tests such as Quantiferon-TB)
    14. Antiphospholipid Antibody profile and Lupus Anticoagulant Profile
    15. Cytokine Panel (e.g. IL1, IL6, IL8, TNFa)
    16. Lactate Dehydrogenase
    17. Uric Acid
    18. Peripheral Smear

VI. Diagnostics

  1. Electrocardiogram
    1. ST Segment Changes
    2. Premature Beats
    3. QTc Prolongation
    4. Atrioventricular Block
    5. Sustained Arrhythmia
  2. Echocardiogram (suspected MIS-C)
    1. Ventricular dysfunction in 30% of cases (rare in Kawasaki Disease)
    2. Coronary Artery dilatation and aneurysms

VII. Imaging

  1. First-Line
    1. Chest XRay

VIII. Differential Diagnosis

  1. Multisystem Infammatory Syndromes
    1. Covid19
    2. Kawasaki Disease
  2. Other Infections
    1. Reactive Infectious Mucocutaneous Eruption (RIME)
    2. Toxic Shock Syndrome
    3. Septic Shock
    4. Mycoplasma pneumonia
    5. Viral Infections (e.g. Adenovirus, other Enteroviruses)
    6. Measles
    7. Tick-Borne Illness
    8. Leptospirosis
    9. Rheumatic Fever
  3. Rheumatologic Conditions
    1. Vasculitis
    2. Systemic Lupus Erythematosus (SLE)
    3. Juvenile Idiopathic Arthritis
    4. Macrophage Activation Syndrome
    5. Hemophagocytic Lymphohistiocytosis
  4. Adverse Drug Reaction
    1. See Serious Cutaneous Adverse Reaction
    2. Stevens-Johnson Syndrome
    3. Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS Syndrome)
  5. Miscellaneous
    1. Malignancy

IX. Evaluation: Severity

  1. Mild MIS-C
    1. Minimal oxygen requirements, minimal end organ injury, negative vasoactive markers
    2. Observed and treated if Kawasaki Disease Criteria met
  2. Kawasaki Disease Criteria Met (with or without coronary ectasias)
    1. Treated with Aspirin, IVIG, with or without Corticosteroids (see below)
  3. Moderate to Severe MIS-C
    1. Indications
      1. Positive vasoactive markers
      2. Ejection Fraction <35%
      3. Significant oxygen requirements
      4. Multi-organ injury
    2. Treatment
      1. Treated with Aspirin, IVIG and Corticosteroids
  4. Refractory MIS-C
    1. Persistent findings despite initial treatment
      1. Fever >24 hours
      2. Worsening or persistent symptoms
    2. Treatment
      1. Give a second dose of IVIG
      2. Consider second dose of immumodulator (e.g. Anakinra)
      3. Consider pulse dosing of Methylprednisolone

X. Management: Indications for Inpatient Evaluation and Management

  1. Cardiac involvement
  2. Hypoxia
  3. Dehydration
  4. Lymphocytes <1000/ul
  5. Platelets <150k or >450k
  6. C-Reactive Protein or CRP >30 mg/L
  7. Erythrocyte Sedimentation Rate or ESR >40 mm/h
  8. Serum Albumin <3 g/dl
  9. Significant Anemia for age
  10. Coagulopathy

XI. Management: General

  1. See Covid19 for respiratory management
  2. Multispecialty Consultation (Infectious disease, hematology and oncology, cardiology, rheumatology)
  3. Management is based on severity (see above)
  4. Immunomodulatory agents, antiplatelet agents and Anticoagulation per Consultation
    1. Low dose Aspirin 3-5 mg/kg/day
      1. If no contraindications (bleeding risk, severe Thrombocytopenia)
      2. Consider therapeutic Anticoagulation
    2. Intravenous Immune Globulin (IVIG) 2 g/kg in single dose
      1. Consider a second dose in refractory cases
    3. Consider Systemic Corticosteroids
      1. Methylprednisolone 1-2 mg/kg/day or 0.5 mg/kg every 6 hours IV
      2. Mixed results when combined with IVIG (lower risk of cardiovascular dysfunction)
      3. Recommended in moderate to severe MIS-C (and consider in an MIS-C case)
      4. McArdle (2021) N Engl J Med 385(1): 11-22 [PubMed]
      5. Son (2021) N Engl J Med 385(1): 23-34 [PubMed]
    4. Consider Immunomodulator in refractory cases
      1. Anakinra (Kineret, IL-1 Receptor Antagonist)
      2. Tocilizumab
  5. Consider empiric Antibiotics when Septic Shock is considered in differential diagnosis
    1. Ceftriaxone (or if Immunocompromised, Cefepime) AND
    2. Consider Vancomycin (if Septic Shock, Meningitis, Central Line) AND
    3. Consider Metronidazole (if suspected abdominal source of infection) AND
    4. Consider Doxycycline (if suspected Tick Borne Illness)
  6. Refractory Hypotension
    1. Norepinephrine is preferred as first-line Vasopressor in Septic Shock (Warm Shock)
    2. Epinephrine is preferred as first-line Vasopressor in cardiac dysfunction (Cold Shock)
    3. PICU admission and consideration for ECMO in refractory cases

XII. Complications

  1. Hypotension or Shock
    1. More common in MIS-C than in Kawasaki Disease

XIII. Resources

  1. Children's Hospital of Philadelphia MIS-C Evaluation Protocol
    1. https://www.chop.edu/clinical-pathway/multisystem-inflammatory-syndrome-mis-c-clinical-pathway
  2. Multisystem Inflammatory Syndrome (CDC)
    1. https://www.cdc.gov/mis/hcp/index.html
  3. American College of Rheumatology
    1. https://www.rheumatology.org/Portals/0/Files/ACR-COVID-19-Clinical-Guidance-Summary-MIS-C-Hyperinflammation.pdf

XIV. References

  1. (2020) University of Minnesota Masonic Guidance on Emergency Management MIS-C in Children
  2. Levy (2024) Mayo Clinic Pediatric Days, lecture attended 1/15/2024
  3. Spivey (2024) Crit Dec Emerg Med 38(6): 18-9
  4. Darby (2021) Am Fam Physician 104(3): 244-52 [PubMed]
  5. Jiang (2020) Lancet Infect Dis [PubMed]
    1. https://www.thelancet.com/action/showPdf?pii=S1473-3099%2820%2930651-4

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