A 6-year-old child from rural India presents with a 3-month history of low-grade fever, weight loss, and persistent cough. Chest X-ray shows hilar lymphadenopathy with minimal parenchymal involvement. Which is the most common site of tuberculosis in children?

Explanation

## Most Common Site of Pediatric TB **Key Point:** Pulmonary tuberculosis with hilar lymphadenopathy is the most common manifestation of TB in children, accounting for 80–90% of all childhood TB cases. ### Why Pulmonary TB Dominates in Children Unlike adults, children with TB typically present with **lymph node disease** rather than cavitary lung disease. The classic radiological finding is **hilar and mediastinal lymphadenopathy** with minimal or no parenchymal consolidation — often called the "primary complex" or Ghon complex when it includes a small peripheral focus. ### Pathophysiology 1. Primary infection occurs at the lung periphery (Ghon focus) 2. Lymphatic spread to hilar/mediastinal nodes (lymphangitis) 3. Hilar node enlargement → airway compression → atelectasis, hyperinflation 4. Most children mount an adequate immune response and contain the infection 5. Progression to active disease occurs in ~5–10% of infected children ### Comparison of TB Sites in Children | Site | Frequency | Age Group | Clinical Features | | --- | --- | --- | --- | | **Pulmonary (with hilar LAD)** | 80–90% | All ages | Cough, fever, weight loss; hilar LAD on CXR | | Miliary TB | 1–3% | <5 years, immunocompromised | Acute onset; miliary pattern on CXR; high mortality | | TB meningitis | 1–3% | <5 years | Meningeal signs, CSF pleocytosis; high morbidity | | Abdominal TB | 5–10% | School age | Abdominal pain, ascites, lymphadenitis | **High-Yield:** Hilar lymphadenopathy **without** significant parenchymal disease is the **hallmark of primary TB in children**. This distinguishes pediatric TB from adult TB, which often shows cavitary lesions and upper-lobe consolidation. **Clinical Pearl:** A child with hilar lymphadenopathy, positive tuberculin skin test (TST), and exposure history requires anti-TB therapy even if sputum smear is negative — diagnosis is often clinical/radiological, not bacteriological. [cite:Nelson Textbook of Pediatrics 21e Ch 345]