From the Guidelines
Extrapulmonary tuberculosis (TB) can affect virtually any organ system outside the lungs, with the most common sites including lymph nodes, pleura, genitourinary system, bones and joints, central nervous system, gastrointestinal tract, and the skin. The pathophysiology involves hematogenous or lymphatic spread of Mycobacterium tuberculosis from a primary pulmonary focus to distant organs 1. According to the official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention clinical practice guidelines, the diagnosis of extrapulmonary TB leads to therapy that improves patient-important outcomes, with high cure rates in most drug-susceptible cases 1.
Common Extrapulmonary Sites
- Lymph nodes (tuberculous lymphadenitis)
- Pleura (tuberculous pleurisy)
- Genitourinary system (renal TB, genital TB)
- Bones and joints (spinal TB or Pott's disease, tuberculous arthritis)
- Central nervous system (tuberculous meningitis, tuberculomas)
- Gastrointestinal tract (intestinal TB, peritoneal TB)
- Skin (cutaneous TB) Other less common sites include the pericardium (tuberculous pericarditis), adrenal glands (Addison's disease), and the eye (ocular TB) 1.
Diagnosis and Treatment
Diagnosis often requires tissue sampling from the affected site for microbiological and histopathological examination, as these forms of TB typically have lower bacterial loads than pulmonary TB, making them more challenging to diagnose 1. The treatment of extrapulmonary tuberculosis relies on the same principles of treatment of pulmonary tuberculosis, with a recommended six-month course of therapy for most sites, and a nine- to 12-month regimen for meningeal TB 1. Corticosteroids may be added to the treatment regimen of patients with tuberculous pericarditis or tuberculous meningitis 1.
From the Research
Extrapulmonary Sites of TB
The extrapulmonary sites of TB include:
- Lymph nodes 2, 3, 4, 5
- Pleura 2, 3, 4
- Bones 3, 4, 6
- Central nervous system 2, 3, 4, 6
- Skin 4
- Ear, nose and throat 4
- Genitourinary system 4
- Pericardium 3, 4, 6
- Gastrointestinal tract 4
- Joints 6
Characteristics of Extrapulmonary TB
Extrapulmonary TB often presents unique diagnostic and therapeutic challenges 4. The clinical manifestations of extrapulmonary TB are diverse and often non-specific 4. Diagnosis is based on a combination of clinical suspicion, imaging, histopathology, and microbiology 4. Treatment of extrapulmonary TB generally follows similar principles to pulmonary TB, but the duration of treatment depends on the site of involvement and the extent of the disease 4, 6.
Diagnosis and Treatment
Diagnosis of extrapulmonary TB is difficult, as microbiological testing mostly requires invasive procedures to obtain a sample for direct proof of tuberculosis by microscopy, culture, molecular methods or histology 3. Nucleic acid amplification tests have greatly facilitated the diagnosis of some forms of extrapulmonary tuberculosis, but their sensitivity is poor and a negative test does not eliminate the diagnosis 2. Treatment follows guidelines of pulmonary tuberculosis, with a two-month regimen consisting of four drugs, followed by a four-month therapy with two drugs 3. Duration of therapy is extended in certain cases, such as tuberculous meningitis or skeletal dissemination 2, 3, 6. Corticosteroids are recommended in cerebral and pericardial tuberculosis 3, 6.