In a pediatric emergency department, how should a child with suspected vasculitis—presenting with fever and a new purpuric rash, persistent abdominal pain, arthralgia, edema, hypertension, hematuria, or neurologic signs—be evaluated and worked up?

Vasculitis Workup in Pediatric Emergency Department

In a pediatric emergency department, immediately obtain CBC with differential, ESR, CRP, comprehensive metabolic panel including creatinine and albumin, urinalysis with microscopy, and blood pressure measurement in any child with suspected vasculitis presenting with fever and purpuric rash, abdominal pain, arthralgia, edema, or neurologic signs.

Initial Clinical Assessment

When evaluating a child for suspected vasculitis, focus your examination on:

• Skin findings: Look specifically for palpable purpura (non-blanching, raised lesions), distribution pattern (lower extremities and dependent areas suggest IgA vasculitis), and presence of petechiae or ecchymoses
• Vital signs: Measure blood pressure in all four extremities to detect hypertension (suggests renal involvement or large vessel vasculitis like Takayasu arteritis) 1
• Cardiovascular: Assess for asymmetric pulses, bruits, and signs of cardiac involvement
• Abdominal examination: Evaluate for tenderness, guarding, or signs of acute abdomen (intussusception or intestinal bleeding can complicate IgA vasculitis) 2
• Musculoskeletal: Document joint swelling, tenderness, or limitation of movement
• Neurologic status: Assess mental status, focal deficits, or signs of encephalopathy

Essential Laboratory Workup

First-Line Tests (Obtain Immediately)

Complete blood count with differential:

• Leukocytosis >13,500/mm³ independently predicts complicated abdominal pain in IgA vasculitis and may help identify children at higher risk of acute abdomen 2
• Thrombocytopenia suggests alternative diagnoses or complications
• Anemia may indicate chronic disease or gastrointestinal bleeding

Inflammatory markers:

• ESR and CRP: Elevated levels support vasculitis diagnosis and help distinguish from non-inflammatory conditions 3, 1
• In children with fever >5 days and 2-3 features suggestive of Kawasaki disease, measure CRP and ESR first 3

Renal function and metabolic panel:

• Creatinine and BUN to assess kidney function
• Albumin <3.5 g/dL is a risk factor in Kawasaki disease 4
• Electrolytes to evaluate for renal involvement

Urinalysis with microscopy:

• Look for hematuria, proteinuria, and red blood cell casts (indicate glomerulonephritis) 5
• Critical pitfall: Normal urinalysis does NOT exclude significant vasculitis—repeated urinalyses may remain negative even with severe systemic involvement and hypertension 6
• Quantify proteinuria with spot urine protein-to-creatinine ratio if dipstick shows ≥2+ protein 5
• Sterile pyuria may occur in Kawasaki disease and should not be dismissed as urinary tract infection 4

Second-Line Tests (Based on Clinical Suspicion)

For suspected Kawasaki disease (fever ≥5 days with clinical features):

• Obtain echocardiography if fever ≥5 days with 2-3 classic features, or if infant <6 months with fever ≥7 days and elevated inflammatory markers 4, 3, 4
• Consider troponin and BNP if cardiac involvement suspected 7
• Liver transaminases (may be elevated) 3

For suspected ANCA-associated vasculitis:

• ANCA testing by both indirect immunofluorescence AND ELISA for PR3 and MPO antibodies 8
• Only order in appropriate clinical context—not as screening test 8

For suspected systemic vasculitis with renal involvement:

• ANA, anti-dsDNA, complement levels (C3, C4)
• Anti-GBM antibodies if rapidly progressive glomerulonephritis suspected 9

For suspected infectious triggers:

• Throat culture or rapid strep test (post-streptococcal glomerulonephritis)
• Hepatitis B and C serology (polyarteritis nodosa, cryoglobulinemic vasculitis)
• HIV testing in appropriate clinical context 9

Imaging Studies

Echocardiography:

• Mandatory for suspected or incomplete Kawasaki disease 4, 3, 4
• May show coronary artery abnormalities, decreased ventricular function, valvular regurgitation, or pericardial effusion even before aneurysm formation 4

Renal ultrasound:

• Indicated when hematuria is accompanied by hypertension, proteinuria, or abnormal renal function 5
• Assess kidney size (small kidneys suggest chronicity), position, and structural abnormalities
• Required before renal biopsy 5

Advanced vascular imaging (MRA, CTA, or catheter angiography):

• Reserved for suspected CNS vasculitis, large vessel vasculitis (Takayasu arteritis), or when diagnosis remains unclear 1, 10, 1
• MRI with contrast abnormal in >90% of primary CNS vasculitis cases 1

Critical Decision Points

When to Admit

Admit immediately if ANY of the following present:

• Shock or significant respiratory distress
• Neurologic changes (altered mental status, focal deficits, meningismus)
• Hypertension (even if urinalysis initially normal) 6
• Abnormal vital signs (tachycardia, tachypnea)
• Signs of acute abdomen or gastrointestinal bleeding
• CRP >10 mg/dL with systemic symptoms 7
• Abnormal troponin, BNP, or EKG findings 7
• Features of Kawasaki disease requiring IVIG treatment 4, 3

When to Consult Subspecialists

Immediate multidisciplinary consultation for admitted patients should include:

• Pediatric rheumatology
• Cardiology (especially for Kawasaki disease or cardiac involvement)
• Nephrology (if hematuria, proteinuria, hypertension, or renal dysfunction)
• Infectious disease 7

Common Diagnostic Pitfalls

1. Mistaking Kawasaki disease for drug reaction: Children presenting with fever and cervical lymphadenopathy may receive antibiotics, and subsequent rash/mucosal changes are incorrectly attributed to antibiotic allergy 4

2. Dismissing sterile pyuria: This finding in Kawasaki disease may be misinterpreted as partially treated UTI with sterile cultures 4

3. Relying solely on urinalysis: Normal urinalysis does NOT exclude significant vasculitis—hypertension and severe systemic involvement can occur with persistently negative urinalysis 6

4. Missing incomplete Kawasaki disease in infants: Young infants (<6 months) may present with fever and minimal clinical features—maintain high suspicion and obtain echocardiography if fever ≥7 days with laboratory evidence of inflammation 4

5. Overlooking prolonged purpura: Purpuric rash lasting >29 days independently predicts complicated abdominal pain in IgA vasculitis 2

Follow-Up Monitoring

For all suspected vasculitis cases (even with initially normal labs):

• Serial blood pressure measurements
• Repeated urinalysis weekly for first month, then monthly for 6 months 6
• Monitor for development of new organ involvement with structured clinical assessments 8