Pulmonary TB | Infectious diseases | NCLEX-RN | Khan Academy

Main ideas and concepts (Pulmonary TB and related pleural TB)

1) Why pulmonary TB gets focused attention

• Pulmonary tuberculosis (TB) is the most common clinical form of TB.
• It accounts for roughly 60–80% of all clinical TB cases worldwide.

2) Primary vs. secondary TB (reactivation) in the lungs

TB disease can arise from:

• Primary TB: the first infection when the host encounters TB for the first time.
• Secondary TB: reactivation of a dormant infection, or infection from a second source in someone previously infected.

Key associations (not necessarily exclusive):

• Primary TB
  • Pulmonary disease tends to be more common in children than adults.
  • Lung involvement is usually lower lobes or middle lobes.
• Secondary TB
  • Lung involvement tends to be upper lobes.

Proposed (imperfectly explained) reasoning:

• The difference may relate to higher oxygen tension in upper lobes, which could facilitate reactivation.

3) Disease severity spectrum and imaging spectrum

Whether primary or secondary, pulmonary TB can occur along a clinical spectrum:

• Mild disease → minimal symptoms.
• Severe disease → progressive lung damage, severe disability, and can lead to death.

Radiographic findings also vary along a spectrum:

• Small infiltrates / minimal chest X-ray abnormalities
• Up to widespread bilateral disease that may show cavitation
  • Cavitation results from lung parenchymal destruction.

4) Natural history if untreated (classic “divided into thirds”)

If pulmonary TB is not recognized and not treated, the historical natural course was described as:

• ~1/3 die from untreated disease
  • Often rapid death (“galloping consumption”).
• ~1/3 spontaneously remit
  • Symptoms and signs resolve and the patient becomes well.
• ~1/3 progress
  • Slower, progressive lung involvement (“consumption” without the “galloping” descriptor).

5) Systemic (nonspecific) symptoms suggesting TB

Common nonspecific systemic features include:

• Weight loss (very common with chronic illnesses)
• Fever lasting days to weeks to months
• Night sweats (often most prominent at night)
• Malaise
• Anorexia (loss of appetite), contributing to weight loss

6) Additional pulmonary signs commonly seen

Symptoms/signs related to progressive lung disease/pneumonia-like illness:

• Cough
• Shortness of breath
• Difficulty breathing, especially when lying down at nighttime (“especially when laying down at nighttime”)

7) TB-associated extrapulmonary skin and eye findings (not fully specific)

Examples mentioned:

• Erythema nodosum
  • Seen as red nodules (illustrated in the video)
  • Not specific to TB; it can also occur with:
    • Some fungal infections (e.g., coccidioidomycosis)
    • Streptococcal infections
  • Still associated with TB
• Phlyctenular conjunctivitis
  • Red eye finding
  • Associated with TB (spelling emphasized as difficult)

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Pleural tuberculosis (pleural TB): main points and diagnostic methodology

1) How pleural TB occurs

Pleural TB is described as distinct from pulmonary TB. Pleural disease can result via:

• Hypersensitivity/immune reaction associated with the primary infection
• Contiguous spread:
  • Direct extension of infection from the lungs into the pleural space
  • Can be from primary and/or secondary disease (as stated)

2) Key clinical distinguishing feature: pleural effusion size

Pleural TB is highlighted because:

• Pleural effusions may be very large
• Effusions can extend extensively along the pleural space side

Clinical implication:

• When you see a large pleural effusion, TB should be considered as a possible cause.

3) How pleural effusion affects exam findings

• Shortness of breath (due to lung compression by fluid)
• Percussion: dull (not air-filled tissue)
• Auscultation: decreased breath sounds
  • Because fluid is between the stethoscope and lung

4) Diagnostic approach: sample pleural fluid first (then escalate)

Best next steps discussed:

• Pleurocentesis / pleural tap to analyze pleural fluid
  • If pleural TB is suspected, sampling is emphasized as essential.

5) Expected pleural fluid findings in TB (typical)

When pleural fluid is obtained, typical findings are:

• Color: “straw” yellowish
• Protein: very high
• Glucose: low to normal
• White cells: ~500 to a few thousand
  • (Also contrasted with bacterial effusions, which may have much higher WBC counts.)

6) TB detection tests on pleural fluid (and performance)

Methods referenced:

• TB-specific stain

  • Ziehl–Neelsen (ZN) stain to look for TB bacteria
  • Sensitivity: positive in about 10–25% of cases when TB is present
  • (Therefore: not very sensitive.)

• Culturing the pleural fluid

  • More sensitive
  • Takes 4–6 weeks
  • Sensitivity: roughly 25–75%

• Pleural biopsy (best yield)

  • If pleural TB is suspected with an effusion, the most recommended test is:
    • Biopsy of the pleura
  • Yield: about 80%
  • Conclusion: pleural biopsy should be done if pleural TB with effusion is suspected.

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Speakers / sources featured

• Charles Prober (voiceover)
• Morgan Theis (voiceover)
• Khan Academy (video/source context via title)