What is the differential diagnosis for a 1-year-old child with fever, multiple aphthous ulcers (canker sores), gingival inflammation, and rashes on the dorsal surface of the tongue?

Differential Diagnosis for a 1-Year-Old with Fever, Multiple Canker Sores, Gingival Inflammation, and Tongue Rash

The most likely diagnosis is primary herpetic gingivostomatitis (HSV-1), which classically presents in the 1-3 year age group with fever, painful oral ulcers involving the gingiva and tongue, and typically lasts approximately 2 weeks. 1, 2

Primary Diagnosis: Primary Herpetic Gingivostomatitis

Primary HSV-1 gingivostomatitis is the leading diagnosis given the age, fever, multiple oral ulcers ("canker sores"), gingival inflammation, and tongue involvement. 1, 2

Key Clinical Features Supporting HSV-1:

• Age specificity: Primary symptomatic HSV infection in children is most prevalent in the 1-3 year age group 1
• Distribution: The disease characteristically involves the buccal and gingival mucosa and the tongue 1
• Associated symptoms: Fever, irritability, tender submandibular lymphadenopathy, and superficial painful ulcers in the gingival and oral mucosa characterize primary HSV gingivostomatitis 3
• Duration: Untreated disease lasts approximately 2 weeks 1

Diagnostic Confirmation:

• Clinical diagnosis is usually made by the appearance of grouped vesicles or ulcers on an erythematous base and patient history 2
• If uncertain, confirm with viral culture, PCR, direct fluorescent antibody testing, or Tzanck preparation (showing multinucleated giant cells with eosinophilic intranuclear inclusions) 3, 2

Critical Differential Diagnoses to Exclude

1. Kawasaki Disease (Must Rule Out)

This is the most important alternative diagnosis to exclude due to potential cardiac complications if missed. 3

When to Suspect Kawasaki Disease:

• Fever for ≥5 days plus oral changes (erythema and cracking of lips, strawberry tongue, erythema of oral mucosa) 3
• Additional features: Bilateral bulbar conjunctival injection without exudate, polymorphous rash, extremity changes (erythema/edema of hands and feet), and cervical lymphadenopathy ≥1.5 cm 3
• Age consideration: Incomplete Kawasaki disease is more common in children younger than 1 year, who paradoxically have higher rates of coronary artery aneurysms if untreated 3

Key Distinguishing Features:

• Kawasaki disease does NOT cause discrete oral ulcers (canker sores); instead, it causes diffuse oral erythema, cracked lips, and strawberry tongue 3
• Exudative pharyngitis and oral ulcerations should prompt consideration of another diagnosis rather than Kawasaki disease 3
• Laboratory findings: ESR often >40 mm/hr (commonly ≥100 mm/hr) and CRP ≥3 mg/dL support Kawasaki disease 3

2. PFAPA Syndrome (Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis)

• Characterized by: Abrupt onset of periodic episodes of high fever with aphthous stomatitis, pharyngitis, and cervical adenitis 4
• Key distinguishing feature: The periodic nature of symptoms (recurring episodes) rather than a single acute presentation 4
• Age consideration: This is a rare childhood disease that can present with oral ulcers coinciding with periodic fever 4

3. Enteroviral Infections (Herpangina)

• Viral pharyngitis can cause fever and oral lesions 3
• Distinguishing features: Herpangina typically causes lesions on the posterior pharynx and soft palate, not the anterior gingiva and tongue 3
• Associated findings: Coryza, cough, diarrhea, and viral exanthem suggest viral etiology 3, 5

4. Streptococcal Pharyngitis with Exanthem

• Age consideration: GAS pharyngitis is uncommon in children <3 years old 3
• Key distinguishing features: Strep throat causes tonsillopharyngeal erythema with or without exudates, palatal petechiae, and beefy red swollen uvula—NOT discrete oral ulcers 5
• In children <3 years: GAS infection is often associated with mucopurulent rhinitis, excoriated nares, and diffuse adenopathy, with exudative pharyngitis being rare 3
• Discrete ulcerative stomatitis (mouth ulcers) suggests viral rather than streptococcal etiology 5

5. Candidiasis (Oral Thrush)

• Presentation: Pseudomembranous candidiasis presents with white plaques that can be scraped off, revealing erythematous base 6
• Less likely given the description of "canker sores" (ulcers) rather than white plaques 6

Recommended Diagnostic Approach

Immediate Assessment:

1. Examine for Kawasaki disease criteria: Check for conjunctival injection, extremity changes, polymorphous rash, and lymphadenopathy ≥1.5 cm 3
2. Document fever duration: If fever ≥5 days with ≥2 Kawasaki features, obtain ESR, CRP, CBC, and echocardiography 3
3. Assess lesion characteristics: Grouped vesicles/ulcers on erythematous base suggest HSV; diffuse erythema without discrete ulcers suggests Kawasaki disease 3, 2

Laboratory Testing:

• If HSV suspected: Viral culture or PCR from lesion swab for definitive diagnosis 3, 2
• If Kawasaki disease cannot be excluded: ESR, CRP, CBC with differential, comprehensive metabolic panel, and urgent echocardiography 3

Management Recommendations

If Primary Herpetic Gingivostomatitis Confirmed:

Oral acyclovir suspension is effective treatment for children with primary herpetic gingivostomatitis and should be started within the first 3 days of disease onset. 1, 2

• Dosing: 15 mg/kg orally 5 times daily for 5-7 days 1
• Evidence: Three randomized double-blind, placebo-controlled trials demonstrated that early acyclovir treatment significantly shortens the duration of all clinical manifestations and infectivity compared with placebo 1
• Supportive care: Maintain hydration, provide analgesics for pain control 2

Critical Pitfall to Avoid:

Do not dismiss this as simple "canker sores" without considering primary HSV gingivostomatitis or excluding Kawasaki disease, especially given the patient's age (1 year old) and fever. The presence of discrete oral ulcers makes Kawasaki disease less likely but does not completely exclude it, particularly in infants who may have atypical presentations. 3