Tuberculosis (TB) lymphadenitis is a bacterial infection of the lymph nodes. It is the most common form of tuberculosis that occurs outside of the lungs, a condition known as extrapulmonary tuberculosis. While caused by the same bacterium as pulmonary TB, its presentation is distinct. The condition requires a specific diagnostic and treatment approach because the infection is contained within the lymphatic system.
Symptoms and Clinical Presentation
The most recognizable sign of tuberculosis lymphadenitis is a slow-growing, painless swelling of the lymph nodes. This enlargement most frequently occurs in the neck, a presentation historically called scrofula, but can also affect lymph nodes in the armpits, groin, or chest. Unlike lymph node swelling from more common infections, the affected nodes in TB lymphadenitis are often firm and not tender to the touch, especially in the initial stages.
While the localized swelling is the primary symptom, some individuals may also experience systemic symptoms. These can include a persistent low-grade fever, unexplained weight loss, fatigue, and drenching night sweats, which can develop gradually. If the condition is not treated, the nodes may become matted together. The tissue inside the node can break down into a cheese-like substance, a process called caseous necrosis, and eventually form a draining sinus that opens through the skin.
Causes and Transmission
Tuberculosis lymphadenitis is caused by the bacterium Mycobacterium tuberculosis. The condition develops when a primary TB infection, which may have been mild or asymptomatic, spreads from the lungs. The bacteria travel to the lymph nodes through the bloodstream or the lymphatic system.
Tuberculosis lymphadenitis itself is not considered contagious. This is because the bacteria are contained within the affected lymph nodes and are not aerosolized by coughing, the primary mode of transmission for pulmonary TB. A weakened immune system is a significant contributor; individuals with HIV, malnutrition, or those taking immunosuppressive medications are more susceptible. The condition is also more prevalent in children and young adults, particularly in regions where tuberculosis is endemic.
The Diagnostic Process
The diagnostic process for tuberculosis lymphadenitis begins with a physical examination and a review of the patient’s medical history. Because other conditions can cause lymph node swelling, a definitive diagnosis requires obtaining a sample from the affected node. The primary diagnostic tool is a biopsy, most often a fine-needle aspiration (FNA). During an FNA, a thin needle is inserted into the lymph node to withdraw a small sample of cells and fluid.
The collected sample is examined cytologically under a microscope for characteristic changes, such as granulomas or caseous necrosis. A portion of the sample is also stained using a method like the Ziehl-Neelsen stain to look for the bacteria. The most definitive test is a bacterial culture, where the sample is placed in a special medium to encourage Mycobacterium tuberculosis to grow.
Imaging studies like ultrasound or CT scans can help visualize the affected lymph nodes and surrounding structures. A chest X-ray is commonly performed to check for any signs of pulmonary TB. Additionally, a tuberculin skin test (TST) or an interferon-gamma release assay (IGRA) blood test can show if the person has been infected with the TB bacterium at some point.
Standard Treatment Regimen
The primary treatment for tuberculosis lymphadenitis is a prolonged course of multiple antibiotic medications. A standard regimen lasts for a minimum of six months and is similar to the treatment for pulmonary TB. This multi-drug approach helps eliminate the bacteria and prevent antibiotic resistance.
The treatment is divided into two phases. The initial phase, lasting about two months, involves a combination of four drugs: isoniazid, rifampin, pyrazinamide, and ethambutol. This is followed by a continuation phase of four months, using just isoniazid and rifampin. Strict adherence to the medications is required for a successful cure.
While medication is the main treatment, surgery has a limited role. A surgical procedure might be used to drain large, painful abscesses or to remove infected nodes that do not respond to the antibiotic regimen.
Prognosis and Recovery
The outlook for individuals with tuberculosis lymphadenitis is excellent, with a very high cure rate, provided the full course of antibiotic treatment is completed. Response to the medication is gradual, and the swollen lymph nodes will slowly decrease in size over several months of therapy.
During or after finishing treatment, some patients might notice that lymph nodes temporarily enlarge again or new ones appear. This is known as a paradoxical reaction and does not indicate treatment failure. After the infection is cured, it is common for some residual firmness or scarring to remain at the site of the affected nodes. A completed treatment regimen resolves the active infection, though TB can recur if a person’s immunity drops significantly later in life.