What is the differential diagnosis for a child with PCR (Polymerase Chain Reaction) confirmed RSV (Respiratory Syncytial Virus) infection, presenting with a painful red tip of the tongue and red papules on the chin?

Differential Diagnosis for Child with PCR-Confirmed RSV and Painful Red Tongue Tip with Red Papules on Chin

The most likely diagnosis is Multisystem Inflammatory Syndrome in Children (MIS-C) or a Kawasaki-like illness, which can occur following or concurrent with viral infections including RSV, and requires immediate evaluation for systemic involvement. 1

Primary Differential Considerations

Multisystem Inflammatory Syndrome in Children (MIS-C)

While MIS-C is most commonly associated with SARS-CoV-2, the clinical presentation described—strawberry tongue and mucocutaneous findings in a child with confirmed viral infection—mirrors the diagnostic criteria for MIS-C. 1 Key features include:

• Strawberry tongue (painful red tip) is a classic mucocutaneous finding in MIS-C and Kawasaki disease 1
• Red papules on chin represent the polymorphic rash component that can be maculopapular or petechial 1
• Concurrent viral infection (RSV in this case) can trigger hyperinflammatory responses 1

Immediate evaluation required: 1

• Complete blood count, comprehensive metabolic panel, ESR, CRP
• Troponin T, BNP, and EKG to assess cardiac involvement
• Consider echocardiography if any cardiac markers are abnormal

Kawasaki Disease

The clinical features overlap significantly with incomplete or atypical Kawasaki disease: 1

• Oral mucosal changes including red/cracked lips and strawberry tongue are diagnostic criteria 1
• Polymorphic rash affecting face and trunk 1
• Can occur following or during viral infections 1

Viral Exanthem with Secondary Bacterial Infection

RSV infection itself can be accompanied by: 1

• Perioral dermatitis from nasal secretions and frequent wiping
• Secondary bacterial infection (impetigo) around mouth/chin from skin breakdown 1
• However, antibacterial medications should only be used when specific indications of bacterial co-infection exist 2

Hand-Foot-Mouth Disease (Enteroviral Co-infection)

Consider concurrent enteroviral infection: 3

• Painful oral lesions affecting tongue tip
• Papular rash on face (though typically hands/feet more prominent)
• Can co-occur with RSV during viral season 3

Critical Red Flags Requiring Immediate Escalation

Admit for multidisciplinary evaluation if any of the following are present: 1

• Abnormal vital signs (tachycardia, tachypnea beyond what RSV alone would cause)
• Neurologic changes including altered mental status or lethargy 1
• Evidence of renal or hepatic injury on metabolic panel 1
• Marked elevation in inflammatory markers (CRP ≥10 mg/dL) 1
• Abnormal EKG findings or elevated BNP/troponin 1

Diagnostic Approach

Tier 1 Screening (Perform Immediately): 1

• Complete blood count
• Comprehensive metabolic panel
• ESR and CRP
• SARS-CoV-2 PCR and serology (to rule out MIS-C)

Tier 2 Complete Evaluation (If screening suggestive): 1

• Troponin T and BNP
• Procalcitonin if available
• EKG
• Blood culture if febrile
• Consider echocardiography

Suggestive laboratory findings for MIS-C/Kawasaki-like illness: 1

• CRP >25 mg/dL
• ESR >40 mm/hour
• Elevated troponin or BNP
• Absolute lymphocyte count <1,000/µL
• Platelet count <150,000/µL
• Sodium <135 mmol/L

Management Considerations

If MIS-C or Kawasaki disease suspected: 1

• Immediate consultation with pediatric rheumatology, cardiology, and infectious disease
• Do not delay evaluation for additional viral testing
• Multidisciplinary team management is essential 1

For RSV management alone (if systemic illness ruled out): 2, 4

• Supportive care with hydration and oxygen if SpO2 <90% 2
• Acetaminophen or ibuprofen for pain/fever 2
• Nasal saline irrigation for symptomatic relief 2
• Avoid corticosteroids, bronchodilators without documented benefit, and antibiotics without bacterial co-infection 2, 4

Common Pitfalls to Avoid

• Do not dismiss mucocutaneous findings as simple viral exanthem without systematic evaluation for inflammatory syndromes 1
• Do not attribute all symptoms to RSV alone when additional concerning features are present 1
• Do not delay cardiac evaluation if any systemic inflammatory markers are elevated 1
• Avoid empiric antibiotics unless documented bacterial co-infection exists 2, 4