A 32-year-old male construction worker from rural Maharashtra presents with a 3-week history of productive cough, low-grade fever in the evenings, and night sweats. He has lost 4 kg over the past month. Sputum smear microscopy is positive for acid-fast bacilli. Chest X-ray shows a cavitary lesion in the right upper lobe with surrounding consolidation and minimal hilar lymphadenopathy. What is the most likely radiological pattern of pulmonary tuberculosis in this patient?

Explanation

## Diagnosis: Fibrocaseous Tuberculosis with Cavitation **Key Point:** The clinical presentation of a sputum smear-positive patient with cavitary disease in the upper lobe is the hallmark of secondary (reactivation) tuberculosis, specifically fibrocaseous TB. ### Radiological Features of Fibrocaseous TB | Feature | Finding in This Case | |---------|----------------------| | **Location** | Right upper lobe (apical-posterior segments) | | **Primary lesion** | Cavitary lesion with irregular walls | | **Associated findings** | Surrounding consolidation, minimal lymphadenopathy | | **Sputum status** | Smear-positive (indicates open cavity) | | **Chronicity** | Subacute presentation (3 weeks) | **High-Yield:** Cavitation in TB occurs due to central caseous necrosis with liquefaction and drainage through a bronchus. This creates the characteristic cavity and renders the patient infectious (smear-positive). **Clinical Pearl:** Upper lobe predominance (especially apical-posterior segments) is due to higher oxygen tension in these zones, which favors mycobacterial growth. ### Why Fibrocaseous and Not Other Patterns? ```mermaid flowchart TD A[TB on CXR]:::outcome --> B{Cavitation present?}:::decision B -->|Yes| C{Location & lymph nodes?}:::decision B -->|No| D{Miliary pattern?}:::decision C -->|Upper lobe + minimal LAD| E[Fibrocaseous TB]:::action C -->|Lower lobe + severe LAD| F[Endobronchial TB] D -->|Yes, diffuse micronodules| G[Miliary TB]:::action D -->|No| H[Primary TB with LAD]:::action E --> I[Smear-positive, infectious]:::outcome ``` **Mnemonic: CAVITY** — **C**aseous necrosis, **A**pical-posterior location, **V**ascular erosion, **I**nfectious (smear+), **T**ypical of secondary TB, **Y**oung adult reactivation.