In a child presenting with fever and rash, what are the Australian paediatric guidelines for immediate assessment, identification of red‑flag features, and appropriate treatment for meningococcal disease, Kawasaki disease, scarlet fever, viral exanthems, and drug‑induced rash?

Fever with Rash in Paediatric Patients: Australian-Aligned Assessment and Treatment

Immediate Red-Flag Assessment

Any child presenting with fever and rash requires immediate evaluation for life-threatening conditions: meningococcal disease, Kawasaki disease, and other serious bacterial infections. 1, 2

Meningococcal Disease Recognition

If any two or more of these features are present, the probability of meningococcal disease is 97%: 3, 2

• Haemorrhagic skin lesions with characteristic appearance (petechiae/purpura)
• Universal distribution of skin haemorrhages across the body
• Maximum diameter of one or more skin haemorrhages >2 mm
• Poor general condition (ill appearance, lethargy)
• Nuchal rigidity

Immediate management for suspected meningococcal disease: 3, 2

• Obtain blood cultures immediately (before antibiotics)
• Administer intravenous ceftriaxone or cefotaxime without delay
• Consider lumbar puncture only if clinically stable and no contraindications
• Do not wait for laboratory confirmation to initiate treatment

Kawasaki Disease Recognition

Kawasaki disease must be considered in any child with unexplained fever ≥5 days, as delayed diagnosis beyond 10 days significantly increases coronary artery aneurysm risk from 25% to 5% with prompt treatment. 4, 1

Classic Kawasaki disease diagnostic criteria (fever ≥5 days PLUS ≥4 of the following 5 features): 4, 5

• Bilateral non-purulent conjunctival injection (bulbar, sparing limbus)
• Oral mucosal changes: cracked/red lips, strawberry tongue, diffuse oral erythema
• Polymorphous rash (maculopapular, erythroderma, or erythema multiforme-like; truncal with groin accentuation)
• Extremity changes: erythema/oedema of hands/feet with sharp demarcation at wrists/ankles
• Cervical lymphadenopathy ≥1.5 cm diameter

Incomplete Kawasaki disease is particularly common in infants <1 year and carries higher risk of coronary complications. 1, 5 If fever ≥5 days with only 2-3 features:

• Measure ESR and CRP immediately 4, 5
• If ESR ≥40 mm/hr and/or CRP ≥3 mg/dL, obtain: complete blood count, comprehensive metabolic panel (albumin, transaminases), urinalysis, and urgent echocardiography 4, 1, 5
• Diagnosis can be made with only 3 clinical features if coronary artery abnormalities are present on echocardiography 4

Treatment for Kawasaki disease: 4

• Intravenous immunoglobulin (IVIG) 2 g/kg as single infusion
• High-dose aspirin 80-100 mg/kg/day divided into four doses
• Treatment must be initiated within 10 days of fever onset to prevent coronary complications

Scarlet Fever Recognition and Treatment

Scarlet fever presents with high fever, strawberry tongue (initially white-coated, then bright red with prominent papillae), and characteristic sandpaper-like rash, most common in children aged 5-15 years. 5

Treatment: 5

• Penicillin V or amoxicillin for 10 days
• Azithromycin for penicillin-allergic patients

Viral Exanthems

Common viral causes include human herpesvirus 6 (roseola), parvovirus B19, Epstein-Barr virus, enteroviruses (coxsackievirus, echovirus), adenovirus. 1, 5, 2

Distinguishing features favouring viral aetiology: 6, 2

• Well appearance despite fever
• Maculopapular (non-haemorrhagic) rash
• Normal capillary refill time
• Absence of nuchal rigidity or lethargy
• ESR <50 mm/hr

Drug-Induced Rash

Drug fever occurs with mean lag time of 21 days (median 8 days) after drug initiation and resolves 1-7 days after discontinuation. 1

Critical pitfall: Do not attribute strawberry tongue and rash solely to antibiotic reaction if the patient was initially treated for presumed bacterial infection—this is a classic missed diagnosis scenario for Kawasaki disease. 5

Age-Specific Considerations

Neonates (0-28 days) with fever and rash: 1

• Highest risk for serious bacterial infection (13% incidence)
• Require comprehensive evaluation including lumbar puncture for CSF analysis
• Consider herpes simplex virus, which can have devastating consequences

Young infants (29-90 days) with fever and rash: 1

• 9% incidence of serious bacterial infection
• Risk-stratify using validated criteria (Rochester or Philadelphia criteria)
• Obtain catheterised urine specimen for culture (never bag specimen)

Infants <1 year with fever ≥5 days: 1, 5

• Incomplete Kawasaki disease is more common in this age group
• Require urgent echocardiography even with minimal clinical features due to high risk of coronary complications
• Do not wait for all 5 classic Kawasaki criteria

Essential Diagnostic Work-Up

For all children with fever and rash, obtain: 1, 6

• Complete blood count with differential
• Inflammatory markers: CRP, ESR
• Blood culture (before antibiotics)
• Urinalysis and catheterised urine culture (if risk factors present)

Additional investigations based on clinical suspicion: 1, 2

• Lumbar puncture if meningeal signs or ill appearance
• Echocardiography if Kawasaki disease suspected
• Coagulation studies if haemorrhagic rash present
• Viral PCR testing (SARS-CoV-2, enterovirus, adenovirus) as indicated

Critical Pitfalls to Avoid

• Do not rely on CRP >6 mg/L alone to identify serious illness—it is poorly correlated with serious bacterial infection in children with fever and petechiae. 6
• Do not use bag-collected urine specimens—they cannot reliably establish urinary tract infection diagnosis due to contamination. 1
• Do not dismiss Kawasaki disease because conjunctivitis is absent—incomplete Kawasaki disease is more common in infants and can present with fewer than 4 principal features. 1, 5
• Do not delay treatment for meningococcal disease while awaiting laboratory confirmation—clinical diagnosis is sufficient to initiate antibiotics. 3, 2
• Do not add vancomycin empirically without specific indications (documented gram-positive infection, catheter-related infection, or persistent fever with clinical deterioration)—this promotes resistance. 1