What is the likely diagnosis and recommended treatment for painful oral sores in a 6-year-old boy?

Oral Sores in a 6-Year-Old Male

The most likely diagnosis is primary herpetic gingivostomatitis (PHGS) caused by herpes simplex virus type 1, and treatment with oral acyclovir 15 mg/kg five times daily for 5-7 days should be initiated within the first 3 days of symptom onset to significantly reduce disease duration and severity. 1, 2

Most Likely Diagnosis: Primary Herpetic Gingivostomatitis

Primary herpetic gingivostomatitis is the most common specific clinical manifestation of primary HSV-1 infection in children, particularly affecting the 1-3 year age group but extending through early childhood. 3, 1, 2

Key Clinical Features to Identify

• Oral lesions: Multiple pin-head vesicles that rapidly rupture to form painful irregular ulcerations covered by yellow-grey membranes, involving the buccal and gingival mucosa and tongue 3, 4
• Systemic symptoms: Fever (mean duration 4.4 days), irritability, malaise, anorexia, and headache as prodromal features 3, 4
• Associated findings: Submandibular lymphadenopathy, halitosis, and refusal to eat or drink 3, 4
• Natural history: Without treatment, oral lesions persist for approximately 12 days, with eating/drinking difficulties lasting 7-9 days 4

Recommended Treatment Protocol

Acyclovir is the drug of choice for treatment of HSV in children, regardless of HIV-infection status. 5

Specific Dosing for Primary Herpetic Gingivostomatitis

• Dose: 15 mg/kg orally, 5 times daily for 5-7 days 1, 2
• Timing is critical: Treatment must begin within the first 3 days of disease onset to be effective 1, 2
• Evidence base: Three randomized double-blind placebo-controlled trials demonstrated that early acyclovir treatment significantly shortens the duration of all clinical manifestations and infectivity compared to placebo 1, 2

Administration Considerations

• Acyclovir may be administered with or without food, as food does not affect absorption 6
• Bioavailability is 10-20% and decreases with increasing dose 6
• Pediatric pharmacokinetics are similar to adults, with mean half-life of 2.6 hours in children aged 7 months to 7 years 6

Supportive Care Measures

Pain and Comfort Management

• Topical anesthetics: Viscous lidocaine 2% can be applied to oral lesions for severe pain 5
• Anti-inflammatory rinses: Benzydamine hydrochloride oral rinse every 3 hours, particularly before eating 5
• Lip care: White soft paraffin ointment applied to lips every 2 hours 5

Oral Hygiene and Infection Prevention

• Antiseptic rinses: 1.5% hydrogen peroxide mouthwash or 0.2% chlorhexidine digluconate twice daily to reduce bacterial colonization 5
• Gentle cleaning: Warm saline mouthwashes or oral sponge to clean the mouth daily 5

Hydration Monitoring

• Critical complication: Dehydration is the main complication, with approximately 8% of children requiring hospitalization for intravenous rehydration 4, 7
• Monitor fluid intake closely and maintain adequate hydration 7

Differential Diagnoses to Consider

While PHGS is most likely in a 6-year-old with painful oral sores, consider these alternatives if clinical features diverge:

When to Suspect Other Diagnoses

• If neutropenia or cytopenias present: Urgent evaluation for acute leukemia with immediate bone marrow biopsy and hematology consultation 8
• If oral AND perianal ulcers: Strongly suggests Crohn's disease requiring urgent colonoscopy 9
• If ulcers persist beyond 2 weeks: Mandatory biopsy to exclude malignancy, autoimmune conditions (pemphigus, pemphigoid, erosive lichen planus), or systemic disease 8, 10

Initial Laboratory Screening if Diagnosis Unclear

• Full blood count to exclude leukemia, anemia, or neutropenia 8, 10
• HIV antibody testing if risk factors present or disease is severe 8, 10
• Fasting blood glucose to exclude diabetes predisposing to fungal infection 8, 10

Critical Clinical Pitfalls to Avoid

• Do not delay acyclovir treatment beyond 72 hours of symptom onset, as efficacy is time-dependent 1, 2
• Do not dismiss dehydration risk in young children who refuse oral intake; monitor closely and have low threshold for IV hydration 4, 7
• Do not perform oral biopsy in acute PHGS, as clinical diagnosis is sufficient; reserve biopsy for ulcers persisting beyond 2 weeks 8, 10
• Do not overlook viral shedding duration (mean 7.1 days), which has implications for transmission to others 4

Expected Clinical Course with Treatment

• Acyclovir significantly shortens duration of oral lesions, fever, eating/drinking difficulties, and viral shedding compared to natural history 1, 2
• Without treatment, expect approximately 12 days of oral lesions and 7-9 days of eating/drinking difficulties 4
• Following resolution, HSV-1 enters latency in nerve ganglia and may reactivate as recurrent herpes labialis 3