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Tuberculosis (TB): Primary and Extrapulmonary Organ Involvement

Primary Site: Lungs (Pulmonary TB) – ~85% of Cases

Inhaled Mycobacterium tuberculosis → alveolar macrophages → granuloma formation (Ghon focus). Reactivation → apical cavitary disease.

Extrapulmonary TB (EPTB) – Common Sites

  1. Lymph nodes: Cervical (scrofula), mediastinal, abdominal. Painless, matted, may suppurate.
  2. Pleura: Exudative effusion; often paucibacillary.
  3. Meninges: Tuberculous meningitis (TBM) – subacute headache, fever, cranial nerve palsies, altered mental status. High mortality without early treatment.
  4. Genitourinary: Kidneys (sterile pyuria, calcifications), epididymis, fallopian tubes → infertility.
  5. Bone & Joint: Pott's disease (spinal TB → gibbus, paraplegia); weight-bearing joints (hip, knee).
  6. Gastrointestinal: Ileocecal region (mimics Crohn's); peritoneal TB (ascites).
  7. Pericardium: Constrictive pericarditis.
  8. Skin: Lupus vulgaris, scrofuloderma, TB verrucosa cutis.
  9. Disseminated (Miliary) TB: Hematogenous spread → innumerable tiny nodules in multiple organs; immunocompromised, young children.

Diagnosis

  • AFB smear/culture, NAAT (Xpert MTB/RIF Ultra), histopathology, IGRA/TST, imaging.

Treatment

Standard 6-month regimen: 2HRZE / 4HR (isoniazid, rifampin, pyrazinamide, ethambutol). Longer for meningitis, bone, CNS. Drug susceptibility testing essential.

Public Health

Airborne precautions; contact investigation; DOT (directly observed therapy); latent TB infection treatment (3HP, 4R, 3HR).

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