Tuberculosis lymphadenitis (TBL) is the most common manifestation of extrapulmonary tuberculosis. This infection specifically targets the lymph nodes. TBL is caused by the bacterium Mycobacterium tuberculosis, the same organism responsible for pulmonary TB. The disease typically involves the lymph nodes in the neck, a presentation historically referred to as scrofula. TBL is a chronic condition that develops slowly, setting it apart from more acute infections.
How Tuberculosis Lymphadenitis Develops
After initial inhalation, Mycobacterium tuberculosis bacteria are taken up by immune cells and spread through the lymphatic system or bloodstream to distant lymph nodes. The bacteria can remain dormant for years following the primary infection. In many cases, TBL represents the reactivation of this latent infection, where the bacteria become active again.
The body’s immune status is a major factor in whether latent infection progresses to active TBL. Immunosuppression from conditions like HIV infection significantly increases the risk, as does malnutrition or close contact with someone who has active pulmonary tuberculosis. TBL is particularly common in children and young adults, and it is observed more frequently in women than men.
Recognizing the Clinical Signs
The characteristic sign of TBL is lymphadenopathy, the painless, gradual swelling of lymph nodes. These enlarged nodes typically feel firm to the touch and are often noticed in the cervical region of the neck. The onset of this swelling is usually insidious, developing over weeks to months, and typically affects only one side of the body.
As the disease progresses, the individual nodes can become fixed and “matted” together due to inflammation of the surrounding tissue, a process called periadenitis. This matting can eventually lead to the formation of a “cold abscess,” a collection of pus lacking the warmth or tenderness typical of other bacterial abscesses. If left untreated, the abscess may spontaneously rupture through the skin, creating a draining sinus or fistula. Systemic symptoms like low-grade fever, night sweats, and unexplained weight loss may occur, but they are often mild or absent.
Diagnostic Confirmation Procedures
Confirming a diagnosis of TBL requires more than just observing clinical signs, as lymphadenopathy has many causes. While blood tests (like IGRAs) and imaging studies (such as CT scans) can support the diagnosis, they are not definitive. Medical confirmation relies on obtaining and analyzing tissue or fluid directly from the affected lymph node.
The least invasive and most common method is Fine Needle Aspiration Cytology (FNAC), which uses a thin needle to collect cells and fluid for examination. Definitive diagnosis often involves excisional biopsy, providing a larger tissue sample. Pathologists look for specific microscopic features, including granulomas and caseous necrosis (a characteristic cheese-like cell death). Samples must also be cultured to grow the M. tuberculosis bacteria and perform drug sensitivity testing. This step determines which medications will be effective against the specific strain.
Standard Treatment Protocols
Treatment for TBL is primarily pharmacological and follows the same multi-drug protocol used for pulmonary tuberculosis. The standard regimen is divided into two phases to eliminate the bacteria and prevent drug resistance. The first, or intensive phase, lasts for two months and involves a combination of four first-line antibiotics:
- Isoniazid
- Rifampicin
- Pyrazinamide
- Ethambutol
The intensive phase is followed by the continuation phase, which lasts for four months and uses only isoniazid and rifampicin. The entire course, totaling six months, is highly effective for uncomplicated TBL. The duration may be extended to nine months in specific situations, such as in patients with HIV infection. Adherence to the full regimen is important to ensure a cure and minimize the risk of recurrence or drug resistance. Surgical intervention, such as incision and drainage, is generally reserved for managing complications like large abscesses or chronic draining sinuses.