Extrapulmonary tuberculosis

Extrapulmonary Tuberculosis (EPTB) refers to tuberculosis (TB) infections that occur outside of the lungs. While pulmonary tuberculosis, which affects the lungs, is the most common form of TB, extrapulmonary TB can affect any part of the body, including the lymph nodes, abdomen, genitourinary tract, skin, joints and bones, and central nervous system. The causative agent of TB, Mycobacterium tuberculosis, is a slow-growing bacterium that can spread from the lungs to other parts of the body through the bloodstream or lymphatic system.

Epidemiology

Extrapulmonary TB accounts for a significant proportion of all TB cases worldwide, with variations in prevalence among different regions and populations. It is more common in individuals with compromised immune systems, such as those with HIV/AIDS, and in children. The distribution of EPTB cases varies globally, with lymphatic and pleural TB being more common in HIV-negative individuals, and disseminated TB more common in HIV-positive patients.

Pathogenesis

The pathogenesis of extrapulmonary TB involves the spread of Mycobacterium tuberculosis from the lungs to other parts of the body, where it can form granulomas or cause systemic disease. The bacteria can be transported by macrophages or can travel directly through the bloodstream or lymphatic system. The exact mechanism of dissemination and the factors determining the site of extrapulmonary involvement are not fully understood but are thought to involve both host and bacterial factors.

Clinical Manifestations

The clinical manifestations of extrapulmonary TB vary depending on the site of infection but generally include fever, weight loss, and site-specific symptoms such as:

• Lymphadenitis: Swollen lymph nodes, often in the neck (scrofula)
• Pleural TB: Pleuritic pain, cough, and effusion
• Skeletal TB: Chronic back pain and stiffness
• Genitourinary TB: Dysuria, flank pain, and hematuria
• Miliary TB: Disseminated disease with fever, weight loss, and multiple organ involvement
• Central Nervous System TB: Meningitis symptoms such as headache, neck stiffness, and photophobia

Diagnosis

Diagnosis of extrapulmonary TB can be challenging due to its varied clinical presentations and the difficulty in obtaining samples from extrapulmonary sites. It typically involves a combination of clinical assessment, imaging studies, and laboratory tests, including:

• Culture: The gold standard for TB diagnosis, involving the cultivation of Mycobacterium tuberculosis from bodily fluids or tissues
• Polymerase Chain Reaction (PCR): A rapid test that can detect TB DNA in clinical samples
• Histopathology: Examination of tissue samples for TB granulomas
• Imaging: X-rays, CT scans, or MRI to identify lesions in affected organs

Treatment

The treatment of extrapulmonary TB is similar to that of pulmonary TB and involves a combination of antibiotics over a period of at least 6 months. The first-line treatment typically includes isoniazid, rifampicin, pyrazinamide, and ethambutol. The duration and specific regimen may vary depending on the site of infection and the patient's response to treatment.

Prevention

Prevention of extrapulmonary TB involves the same strategies as pulmonary TB, including early detection and treatment of active TB cases, vaccination with Bacille Calmette-Guérin (BCG) vaccine, and treatment of latent TB infection, especially in high-risk individuals.

See Also

• Tuberculosis
• Pulmonary tuberculosis
• Mycobacterium tuberculosis
• BCG Vaccine
• HIV/AIDS