Primary and latent tuberculosis vs Secondary/reactivation tuberculosis
How to tell Primary and latent tuberculosis and Secondary/reactivation tuberculosis apart when a board question makes them look alike.
Primary TB is initial Ghon/hilar disease; latent TB is positive test without symptoms; secondary TB is apical cavitary contagious reactivation.
Side by side
Primary TB often involves middle/lower lung zones with hilar lymphadenopathy and a Ghon focus/complex; latent TB has positive immune testing without symptoms or contagious active disease.
Secondary/reactivation TB classically affects apical upper lobes with cavitary lesions, cough, fever, night sweats, weight loss, hemoptysis, and contagious active disease.
Initial inhaled Mycobacterium tuberculosis establishes a primary focus and lymph node involvement; immune containment can create latent infection.
Reactivation occurs when contained organisms resume replication, especially with impaired cellular immunity, producing tissue destruction and cavitation.
Positive IGRA or tuberculin test with normal chest imaging and no symptoms supports latent TB; Ghon complex and hilar nodes support primary TB.
Acid-fast bacilli smear/culture or NAAT, apical cavitation, systemic symptoms, and airborne infectiousness support active secondary TB.
The trap
A positive IGRA alone does not prove active TB; symptoms, imaging, and microbiology decide active disease.
Watch it explained
Test it nowThe repair move
For TB stems, separate immune memory, initial lung/lymph node pattern, and active cavitary reactivation.
Try a free question
CoreA child recently exposed to TB has a lower-lobe parenchymal focus with ipsilateral hilar lymphadenopathy. Which pattern is most likely?
Show answer and explanation
Answer: A. Primary tuberculosis. Initial TB with Ghon focus and hilar lymph node involvement supports primary tuberculosis.
Why the other choices are tempting
- B. Secondary TB classically causes apical cavitary reactivation disease.
- C. Latent TB has positive immune testing without symptoms or active radiographic disease.
- D. Sarcoidosis causes noncaseating granulomas and bilateral hilar lymphadenopathy.
- E. Histoplasmosis can calcify nodes but is a fungal infection, not classic primary TB pattern.
Flashcards
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What lesion supports primary tuberculosis?
A Ghon focus with hilar lymph node involvement supports primary tuberculosis.
What defines latent tuberculosis?
Positive TB immune testing without symptoms or radiographic/microbiologic active disease defines latent TB infection.
Quick answers
What is the fastest way to tell Primary and latent tuberculosis from Secondary/reactivation tuberculosis?
Primary TB is initial Ghon/hilar disease; latent TB is positive test without symptoms; secondary TB is apical cavitary contagious reactivation.
What is the key clue for Primary and latent tuberculosis?
Primary TB often involves middle/lower lung zones with hilar lymphadenopathy and a Ghon focus/complex; latent TB has positive immune testing without symptoms or contagious active disease.
What is the key clue for Secondary/reactivation tuberculosis?
Secondary/reactivation TB classically affects apical upper lobes with cavitary lesions, cough, fever, night sweats, weight loss, hemoptysis, and contagious active disease.
What is the common trap with Primary and latent tuberculosis vs Secondary/reactivation tuberculosis?
A positive IGRA alone does not prove active TB; symptoms, imaging, and microbiology decide active disease.