An 8-year-old boy from Delhi presents with a 2-month history of persistent cough, low-grade fever, and night sweats. His father was treated for smear-positive pulmonary TB 6 months ago. On examination, the child is afebrile but appears chronically ill. Chest X-ray shows right upper lobe infiltration with a small cavity. Mantoux test (5 TU) shows 14 mm induration. Sputum smear microscopy (×3) is negative. Gastric aspirate AFB smear is positive. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Progressive Primary Tuberculosis with Early Cavitation ### Understanding the Spectrum of Primary TB Progression **Key Point:** Primary TB can progress to adult-type disease with cavitation, especially in children >5 years or those with delayed diagnosis and continued exposure. ### Pathophysiology of Progressive Primary TB Progressive primary TB occurs when: 1. Initial primary complex (Ghon focus + lymphangitis + lymphadenitis) fails to resolve 2. Erosion of caseous lymph node material into adjacent bronchus → bronchial spread 3. Parenchymal infiltration and cavity formation in upper lobes (gravity-dependent) 4. Transition from closed lesion to open, communicating cavity ### Key Diagnostic Features in This Case | Feature | Finding | Significance | |---------|---------|---------------| | **Age** | 8 years | Older child; can develop cavitary disease | | **CXR pattern** | Right upper lobe infiltration + small cavity | Progressive primary TB, not simple hilar lymphadenopathy | | **Sputum smear (×3)** | Negative | Cavity is small; limited bacillary load in sputum | | **Gastric aspirate AFB** | Positive | Gold standard for diagnosis in children (swallowed sputum) | | **Mantoux** | 14 mm (positive) | TB infection confirmed | | **Duration** | 2 months | Subacute presentation typical of progressive TB | | **Exposure history** | Father with smear-positive TB | Recent, ongoing exposure | **High-Yield:** In children, **gastric aspirate AFB is more sensitive than sputum smear** because children swallow sputum rather than expectorate. A positive gastric aspirate AFB in a child with TB-suggestive CXR changes confirms active TB disease. ### Why This Is NOT Latent TB - **Latent TB** = TB infection without disease (positive Mantoux, negative CXR, no symptoms) - This child has **active disease**: fever, cough, CXR changes, and positive gastric aspirate AFB ### Radiological Clue: Upper Lobe Cavitation Upper lobe involvement with cavitation in an 8-year-old indicates: - Progression from primary TB to adult-type pattern - Likely due to continued exposure and/or delayed diagnosis - Requires standard 4-drug anti-TB therapy (not just isoniazid preventive therapy) **Clinical Pearl:** A child with TB exposure, constitutional symptoms, upper lobe infiltration, and positive gastric aspirate AFB has **active TB disease** and requires full anti-TB therapy, even if sputum smear is negative. ### Management - Start 4-drug anti-TB therapy: HRZE for 2 months, then HR for 4 months - Nutritional support and vitamin B6 - Contact tracing and preventive therapy for household contacts - Monitor for complications (bronchial obstruction, atelectasis) [cite:Park 26e Ch 9; Nelson 21e Ch 219]