A 6-year-old boy from Delhi is brought to the pediatric outpatient clinic by his mother with a complaint of persistent cough for 6 weeks and recurrent low-grade fever. His father was treated for pulmonary TB 8 months ago (now on continuation phase). On examination, the child is afebrile, respiratory rate 24/min, no lymphadenopathy, and lungs are clear on auscultation. Chest X-ray shows a 2 cm right hilar lymph node with mild peribronchial thickening but no parenchymal consolidation. Mantoux test (5 TU) shows 8 mm induration at 48 hours. Sputum smear microscopy (induced sputum) is negative. What is the most appropriate diagnosis?

Explanation

## Distinguishing LTBI from TB Disease in Children **Key Point:** The presence of **symptoms + radiological findings** in a child with TB exposure indicates **TB disease** (active TB), NOT latent infection. Treatment differs fundamentally between these two states. ### Clinical Differentiation | Feature | LTBI | TB Disease (Intrathoracic TB) | |---------|------|------------------------------| | **Symptoms** | None | Cough >2 weeks, fever, weight loss | | **Chest X-ray** | Normal | Hilar LAD, infiltrates, or peribronchial changes | | **Mantoux** | Positive (≥5 mm) | Positive (≥5 mm) | | **Sputum/Culture** | Negative | Negative (in children) or positive | | **Treatment** | INH monotherapy × 6 months | HRZE × 2 months + HR × 4 months | | **Infectivity** | Non-infectious | May be infectious (if cavitary) | **High-Yield:** This child has **3 cardinal features of TB disease**: (1) **symptoms** (cough 6 weeks + fever), (2) **radiological findings** (hilar LAD + peribronchial thickening), and (3) **TB exposure** (father with active TB). This is **TB disease**, not LTBI. ### Why This Is TB Disease, Not LTBI 1. **Symptomatic** (cough 6 weeks, fever) → rules out asymptomatic LTBI 2. **Radiological abnormality** (hilar LAD + peribronchial thickening) → indicates active disease 3. **Recent exposure** (father diagnosed 8 months ago) → suggests recent infection progressing to disease 4. **Positive Mantoux** (8 mm in <5 years with contact) → consistent with recent TB infection **Clinical Pearl:** In children, **intrathoracic TB** (hilar lymphadenitis ± peribronchial inflammation) is the most common form of TB disease. It is NOT always cavitary or smear-positive. Diagnosis is clinical + radiological, not microbiological. ### Mnemonic for TB Disease Features **CRAM** = **C**ough + **R**adiological findings + **A**ctive exposure + **M**antoux positive → **TB Disease** ### Treatment Regimen ```mermaid flowchart TD A[TB Disease Diagnosed]:::outcome --> B[Intensive Phase: 2 months]:::action B --> C[HRZE daily]:::action C --> D[Continuation Phase: 4 months]:::action D --> E[HR daily]:::action E --> F[Total Duration: 6 months]:::outcome ``` **Dosing in children (weight-based):** - **H (Isoniazid):** 10 mg/kg/day (max 300 mg) - **R (Rifampicin):** 15 mg/kg/day (max 600 mg) - **Z (Pyrazinamide):** 25 mg/kg/day (max 2 g) - **E (Ethambutol):** 20 mg/kg/day (max 1.2 g) **Monitoring:** Monthly clinical review, weight gain, adherence. Baseline and follow-up LFTs (especially for Z and R). Vitamin B6 supplementation to prevent INH-induced neuropathy.