Extra-pulmonary tuberculosis refers to the tuberculosis infection that occurs outside lungs. Its tricky appearance, like any other chronic illness, makes it difficult to diagnose. It can easily be confused with other non-respiratory diseases.

Unlike pulmonary tuberculosis, extra-pulmonary TB can be characterised by lymph node that refers to swelling of the particular region of the body located near or distantly from the site of infection.

Extra-pulmonary tuberculosis commonly involves the mobility impairment (spine), severe headache and neurological dysfunction as seen in TB meningitis.

Extra-pulmonary tuberculosis is a non-contagious form of TB. It is not commonly accompanied with cough and high grade fevers as with pulmonary tuberculosis. However, both the contagious and non-contagious forms of tuberculosis need aggressive treatment as they can be fatal.

For extra-pulmonary tuberculosis, blood or lymphatic spread of tubercle bacilli to body parts outside lungs can occur at the time of primary infection.

Some people possess strong immune system that can resist transmission of the bacilli and in fully immune-competent individuals, the bacilli can be destroyed.

When who presents with immune deficit, some bacteria can concentrate or accumulate at a particular site where they may lie dormant for a long time before you fall sick or disease start to manifest.

Sometimes the bacteria can be coughed from the lungs and swallowed. By this route, they may enter the lymph nodes of the neck or parts of the gastro-intestinal (GI) tract.

Before milk was routinely pasteurised, cattle infected with the bovine variant of tuberculosis could pass disease to humans who drank infected milk. Transmission by this route would also give rise to gastro-intestinal diseases.

The commonest sites of infection are lymph glands and abscesses, particularly around the neck, the orthopedic sites such as bones and joints. The spine is affected in about half such cases.

In women, the uterus is the most common whereas in men the epididymis is the site most frequently affected. Both sexes are affected by renal, ureteric or bladder disease equally. In the abdomen, the TB commonly affects the bowels.

Other diseases linked to Extra-pulmonary tuberculosis include meningitis, pericardium the outer layer of the heart muscles, which causes constriction to the heart, may be affected. On the skin surface, there is the lupus vulgaris form that manifests in a wolf-like appearance, especially in facial region.

Tuberculous meningitis can cause or bring about a variety of symptoms. For example, an affected cranial nerve can lead to double vision. There may also be mental confusion developing over days or weeks. If not detected and treated, coma may develop. If treated early, recovery may be complete, but long-term sequelae are likely if the treatment is delayed.

Clinical presentation

Clinical presentation is characteristically chronic with pain and swelling being the principal features.

Lymph glands of the neck may develop singly or in chains. They swell and pain and may have a rubbery texture. They may break down to give abscess formation. These may discharge onto the skin giving a very unsightly combination of swelling and pus around the neck.

Bony disease causes pain and swelling of the affected part. Spinal disease may cause paraplegia most of the vertebrae is destroyed to cause instability of the spine.

Abdominal disease characteristically causes pain and constipation. If advanced it may cause complete obstruction of the bowel.

Diagnosis

The diagnosis at any site should be confirmed by obtaining specimens for bacteriology wherever possible. This means that fluid aspirated or biopsies taken should be placed in a medium such as saline which will not kill the bacteria.

Too often, still biopsy specimens are placed in formalin so that bacteriological confirmation including sensitivity testing cannot be done.

Treatment

Treatment is like for pulmonary disease with isoniazid, rifampicin, pyrazinamide and ethambutol for two months followed by isoniazid and rifampicin for four months, except for central nervous system disease when treatment should be continued for a full year.

Steroids may be used in pericardial and meningeal disease. Surgery is usually unnecessary especially where lymph glands and abscess are present as long-term discharging sinuses may result.

Surgery is sometimes necessary in spinal TB where there is instability and may be needed to overcome strictures in gastro-intestinal disease.

Occasionally pericardectomy may be required when pericardial disease causes tamponade in case of heart infection due to extra-pulmonary TB. Dr Joseph Kamugisha is a resident oncologist at Jerusalem Hospital, Israel