What is the recommended treatment for a young child with latent tuberculosis (TB) infection, as indicated by a positive Purified Protein Derivative (PPD) test result of 14 mm, who is asymptomatic with a clear chest x-ray and has been exposed to a family member with TB?

Chemoprophylaxis for Latent TB in Young Child with Household Exposure

This young child with a positive PPD (14 mm), clear chest x-ray, and documented household TB exposure should receive immediate chemoprophylaxis for latent TB infection without requiring IGRA confirmation. 1

Rationale for Immediate Treatment Without IGRA

• Young children (<5 years) exposed to infectious TB require chemoprophylaxis regardless of tuberculin test results because they are at highest risk for progression to severe disease, including meningeal and disseminated TB 1

• The PPD result of 14 mm is definitively positive (equivalent to Heaf grade 2-3), meeting threshold criteria for treatment in a child with documented TB contact 1

• IGRA testing is not necessary when the tuberculin skin test is already positive in a young child with known TB exposure 1. IGRA may be used to confirm positive tuberculin tests in older children to increase specificity, but in this clinical scenario with clear exposure history and positive PPD, it would only delay necessary treatment 1

• The positive and negative predictive values of IGRAs remain poorly established in children, making them less reliable than in adults 1

Recommended Treatment Regimen

Two acceptable options exist:

Option 1: Isoniazid for 9 months (preferred in most guidelines)

• Dosing: 10-15 mg/kg daily (maximum 300 mg) as directly observed therapy or self-administered 1
• Efficacy: 70-90% risk reduction in children 1
• Safety: Minimal hepatotoxicity risk in children; routine liver enzyme monitoring not necessary unless risk factors present 1
• Pyridoxine supplementation: Not routinely required but consider for breastfeeding infants or children with dietary deficiencies 1

Option 2: Rifampicin + Isoniazid for 3 months

• Dosing: Rifampicin 10 mg/kg (maximum 600 mg) + Isoniazid 10 mg/kg (maximum 300 mg) daily 1
• Advantages: Shorter duration improves adherence; programmatic data from UK shows effectiveness 1, 2
• Evidence: Long-term follow-up shows <1/1000 person-years progression to active TB 2

Critical Management Points

Before initiating chemoprophylaxis:

• Active TB must be excluded through clinical examination and chest radiography (already done in this case) 1
• Confirm the father's TB is drug-susceptible; if isoniazid-resistant, use rifampicin alone for 4-6 months 1

Monitoring during treatment:

• Clinical assessment for symptoms of hepatotoxicity (nausea, vomiting, abdominal pain, jaundice) 1
• Liver function testing only if symptoms develop or if pre-existing liver disease risk factors 1
• Discontinue therapy if transaminases exceed 3× upper limit of normal with symptoms or 5× without symptoms 1

Common Pitfalls to Avoid

• Do not delay treatment waiting for IGRA results in young children with documented exposure and positive tuberculin tests 1
• Do not use once-weekly rifapentine + isoniazid regimens in children under 2 years (this child's exact age matters; if ≥2 years, 12-week once-weekly rifapentine 300-900 mg + isoniazid could be considered as alternative) 3
• Do not stop treatment prematurely even if child remains asymptomatic; untreated young children with latent TB have up to 40% risk of progression to active disease 1
• Do not use monotherapy as this risks development of drug resistance if unrecognized active disease exists 1

Special Considerations for This Case

Given the father has active TB, ensure:

• Infection control measures are in place in the household 1
• All household contacts are screened for TB infection and disease 1
• The father receives appropriate directly observed therapy to prevent ongoing transmission 1
• Follow-up at 3 and 6 months to assess adherence and monitor for development of active disease 4