What is the management approach for an 11-year-old with fever, rash, leukocytosis, and elevated CRP?

Management of an 11-Year-Old with Fever, Rash, and Marked Leukocytosis

This child requires immediate hospital admission for urgent evaluation of multisystem inflammatory syndrome in children (MIS-C) or other serious hyperinflammatory conditions, given the combination of fever, rash, extreme leukocytosis (WBC 38,000), and elevated inflammatory markers. 1

Immediate Diagnostic Priorities

Tier 1 Screening (Urgent)

• SARS-CoV-2 testing is mandatory - obtain both PCR and serology immediately, as MIS-C is temporally associated with COVID-19 and represents a life-threatening complication 1
• Complete the inflammatory workup - you already have WBC and CRP; immediately add ESR, complete metabolic panel (looking specifically for hyponatremia, hypoalbuminemia, elevated creatinine, and liver enzyme abnormalities) 1, 2
• Assess for lymphopenia, thrombocytopenia, or neutrophilia on the differential count, as these support MIS-C diagnosis 1

Critical Clinical Assessment

Admit this child immediately if ANY of the following are present: 1

• Abnormal vital signs (tachycardia, tachypnea)
• Any degree of respiratory distress
• Neurologic changes (altered mental status, confusion, headache, focal deficits)
• Signs of dehydration or shock
• Abdominal pain or gastrointestinal symptoms

The CRP of 4 mg/dL is elevated but below the highly concerning threshold of >10 mg/dL that typically characterizes severe MIS-C; however, the extreme leukocytosis (38,000) is highly abnormal and demands urgent investigation 1

Tier 2 Evaluation (Hospital-Based)

Cardiac Assessment (Non-Negotiable)

• EKG and echocardiogram are mandatory - MIS-C causes left ventricular dysfunction in 20-55% of cases and coronary artery abnormalities in ~20% of cases 1
• Troponin T and BNP/NT-proBNP levels - highly elevated BNP may identify cardiac involvement even before clinical manifestations 1, 2
• Monitor for arrhythmias - atrioventricular block occurs in up to 20% of MIS-C cases 1

Extended Laboratory Panel

• D-dimer, ferritin, LDH, procalcitonin - these are frequently elevated in MIS-C and help distinguish from other conditions 1, 2
• Blood cultures and evaluation for bacterial sepsis - the extreme leukocytosis could represent overwhelming bacterial infection, which must be excluded 3, 4
• Albumin level - hypoalbuminemia is common in MIS-C and indicates more severe systemic inflammation 1, 2

Differential Diagnosis Considerations

MIS-C vs. Kawasaki Disease

MIS-C differs from classic Kawasaki disease in several key ways: 1

• Broader age range (MIS-C affects older children more commonly)
• More prominent gastrointestinal and neurologic symptoms
• Higher likelihood of shock and cardiac dysfunction (arrhythmias, ventricular dysfunction)
• More common in African, Afro-Caribbean, and Hispanic children; less common in East Asian descent

Other Critical Diagnoses to Exclude

• Bacterial sepsis or toxic shock syndrome - the WBC of 38,000 with fever and rash could represent overwhelming bacterial infection requiring immediate antibiotics 3, 5
• Acute leukemia - extreme leukocytosis in a child with fever requires peripheral blood smear examination to exclude blast cells 2
• Drug-induced neutrophilic dermatosis (Sweet syndrome) - obtain medication history, though this typically shows neutrophilia not this degree of leukocytosis 6

Treatment Algorithm

If MIS-C is Confirmed

First-line therapy consists of: 1

• IVIG 2 gm/kg (based on ideal body weight; may divide over 2 days if cardiac dysfunction present)
• Consider adding methylprednisolone 1-2 mg/kg/day if the child has concerning features (ill appearance, unexplained tachycardia, elevated BNP) even without shock

Intensification therapy for refractory disease: 1

• Methylprednisolone IV 10-30 mg/kg/day OR
• High-dose anakinra
• Refractory disease = persistent fevers and/or ongoing significant organ involvement despite first-line therapy

Multidisciplinary Team Required

Immediate consultation with: 1

• Pediatric rheumatology
• Pediatric cardiology
• Pediatric infectious disease
• Pediatric hematology (given the extreme leukocytosis)

Critical Pitfalls to Avoid

• Do not delay SARS-CoV-2 testing - MIS-C can occur 2-6 weeks after COVID-19 infection, and serology may be positive even when PCR is negative 1
• Do not assume this is "just a viral rash" - the combination of extreme leukocytosis (38,000) with fever and rash represents a medical emergency until proven otherwise 5
• Do not wait for all test results before admitting - this child meets criteria for immediate hospitalization based on marked elevation of inflammatory markers alone 1
• Do not miss cardiac involvement - cardiac complications are the primary cause of morbidity and mortality in MIS-C, and early detection is critical 1