What are the symptoms of Multisystem Inflammatory Syndrome in Children (MIS-C)?

Symptoms of Multisystem Inflammatory Syndrome in Children (MIS-C)

The primary symptoms of MIS-C include persistent fever (≥38.0°C for ≥24 hours or ≥3 days), gastrointestinal manifestations (abdominal pain, diarrhea, vomiting), mucocutaneous findings (rash, conjunctivitis, red/cracked lips, strawberry tongue), and cardiovascular involvement often progressing to shock. 1

Core Clinical Features

Cardinal Symptoms (Present in Most Cases)

• Fever: Present in nearly 100% of cases 2
• Gastrointestinal symptoms (77-94% of cases):
  • Abdominal pain (most common)
  • Diarrhea
  • Vomiting 2, 3
• Mucocutaneous manifestations (63-68% of cases):
  • Polymorphic rash (maculopapular or petechial, not vesicular)
  • Bilateral conjunctivitis (without exudate)
  • Red/cracked lips
  • Strawberry tongue
  • Erythema of oropharyngeal mucosa
  • Swollen hands and feet 1

Common Additional Symptoms

• Headache (68%) 3
• Lymphadenopathy (especially cervical) 1
• Neck swelling 1
• Sore throat 1
• Syncope 1
• Confusion or altered mental status 1

Organ System Involvement

Cardiovascular (Very Common)

• Myocardial dysfunction (40-53% of cases)
• Pericarditis (20%)
• Coronary artery abnormalities (13%)
• Shock (14-23% requiring intensive care) 2, 3
• Elevated cardiac markers (troponin in 41%, NT-pro-BNP in 50%) 2

Respiratory

• Respiratory symptoms in 28% of cases 4
• Cough 1
• Respiratory distress (less common than in acute COVID-19) 4

Neurological

• Headache
• Altered mental status
• Encephalopathy
• Focal neurologic deficits
• Meningismus
• Seizures (10.5%) 3
• Papilledema 1

Renal

• Acute kidney injury (26%) 3

Hematologic

• Lymphopenia (84%)
• Thrombocytopenia (37%) 3

Laboratory Findings

Inflammatory Markers (Markedly Elevated)

• C-reactive protein (CRP) >10 mg/dL (often >15 mg/dL)
• Elevated erythrocyte sedimentation rate (ESR)
• Elevated ferritin
• Elevated procalcitonin
• Elevated D-dimer
• Elevated IL-6 1

Other Laboratory Abnormalities

• Neutrophilia
• Lymphopenia
• Hypoalbuminemia
• Hyponatremia (Na <135 mmol/L)
• Elevated liver enzymes 1

Warning Signs Requiring Immediate Medical Attention

• Abnormal vital signs (tachycardia, tachypnea)
• Respiratory distress of any severity
• Neurologic deficits or changes in mental status (even subtle)
• Evidence of renal or hepatic injury
• Marked elevations in inflammation markers (CRP >10 mg/dL)
• Abnormal EKG or elevated cardiac markers 1

Distinguishing Features from Kawasaki Disease

MIS-C differs from Kawasaki Disease in several important ways:

• Affects a broader age range (median age 8-12 years vs. typically <5 years for KD)
• More prominent gastrointestinal and neurologic symptoms
• Higher likelihood of shock and cardiac dysfunction
• Lower platelet counts and lymphocyte counts
• Higher CRP levels
• Higher incidence in children of African, Afro-Caribbean, and Hispanic descent 1

Timing and Association with COVID-19

MIS-C typically develops 2-6 weeks after SARS-CoV-2 infection, often after the acute infection has resolved 1. This temporal association is critical for diagnosis, as many patients may have negative PCR tests but positive serology for SARS-CoV-2 1.

Remember that MIS-C is a rare but serious complication of SARS-CoV-2 infection, with an estimated incidence of 0.69 per 1,000 SARS-CoV-2 infections 2. Early recognition of these symptoms and prompt medical attention are essential for reducing morbidity and mortality.