Tuberculosis Health Dictionary

An infectious disease, commonly called , caused in humans by the bacterium MYCOBACTERIUM TUBERCULOSIS. is usually transmitted in airborne droplets expelled when an infected person coughs or sneezes. An inhaled droplet enters the lungs and the bacteria begin multiplying. The immune system usually seals off the infection at this point, but in about 5 per cent of cases the infection spreads to the lymph nodes. It may also spread to other organs through the bloodstream, which may lead to miliary tuberculosis, a potentially fatal form of the disease.

In about another 5 per cent of cases, bacteria held in a dormant state by the immune system become reactivated months, or even years, later. The infection may then progressively damage the lungs, forming cavities.

The primary infection is usually without symptoms. Progressive infection in the lungs causes coughing (sometimes bringing up blood), chest pain, shortness of breath, fever and sweating, poor appetite, and weight loss. Pleural effusion or pneumothorax may develop. The lung damage may be fatal.

A diagnosis is made from the symptoms and signs, from a chest X-ray, and from tests on the sputum. Alternatively, a bronchoscopy may also be carried out to obtain samples for culture.

Treatment is usually with a course of 3 or 4 drugs, taken daily for 2 months, followed by daily doses of isoniazid and rifampicin for 4–6 months. However, bacteria are increasingly resistant to the drugs used in treatment, and others may have to be used and treatment carried out for a longer period. If the full course of drugs is taken, most patients recover.

can be prevented by BCG vaccination, which is offered routinely at birth or age 10–14.

Any contacts of an infected person are traced and examined, and, if infected, are treated early to reduce the risk of the infection spreading.

Tuberculosis results form infection with Mycobacterium tuberculosis. The lungs are the site most often affected, but most organs in the body can be involved in tuberculosis. The other common sites are LYMPH NODES, bones, gastrointestinal tract, kidneys, skin and MENINGES.

The weight loss and wasting associated with tuberculosis before treatment was available led to the disease’s popular name of consumption. Enlargement of the glands in the neck, formerly called scrofula, was known also as the ‘king’s evil’ from the supersition that a touch of the royal hand could cure the condition. Lupus vulgaris (see under LUPUS) is another of the skin manifestations of the disease.

The typical pathological change in tuberculosis involves the formation of clusters of cells called granulomas (see GRANULOMA) with death of the cells in the centre producing CASEATION.

It is estimated that there are 7–8 million new cases of tuberculosis worldwide each year, with 2–3 million deaths. The incidence of tuberculosis in developed countries has shown a steady decline throughout the 20th century, mainly as a result of improved nutrition and social conditions and accelerated by the development of antituberculous chemotherapy in the 1940s. Since the mid-1980s the decline has stopped, and incidence has even started to rise again in inner-city areas. In 2002, 7,239 cases of tuberculosis were noti?ed in the UK compared with 6,442 a decade earlier; more than 390 deaths in 2003 were attributed to the disease. Factors involved in this rise are immigration from higher-prevalence areas, poorer social conditions and homelessness in some urban centres and the association with HIV infection and drug abuse. The incidence of tuberculosis is also rising in many developing countries because of the emergence of resistant strains of the tubercle bacillus (see below). In the UK recently there have been serious outbreaks in a handful of urban-based schools.

(TB) n. an infectious disease caused by the bacillus Mycobacterium tuberculosis (first identified by Koch in 1882) and characterized by the formation of nodular lesions (tubercles) in the tissues.

In pulmonary tuberculosis – formerly known as consumption and phthisis (wasting) – the bacillus is inhaled into the lungs where it sets up a primary tubercle and spreads to the nearest lymph nodes (the primary complex). Natural immune defences may heal it at this stage; alternatively the disease may smoulder for months or years and fluctuate with the patient’s resistance. Many people become infected but show no symptoms. Others develop a chronic infection and can transmit the bacillus by coughing and sneezing. Symptoms of the active disease include fever, night sweats, weight loss, and the spitting of blood. In some cases the bacilli spread from the lungs to the bloodstream, setting up millions of tiny tubercles throughout the body (miliary tuberculosis), or migrate to the meninges to cause tuberculous *meningitis. Bacilli entering by the mouth, usually in infected cows’ milk, set up a primary complex in abdominal lymph nodes, leading to *peritonitis, and sometimes spread to other organs, joints, and bones (see Pott’s disease).

Tuberculosis is curable by various combinations of the antibiotics *streptomycin, *ethambutol, *isoniazid (INH), *rifampicin, and *pyrazinamide. Preventive measures in the UK include the detection of cases by X-ray screening of vulnerable populations and vaccination with *BCG vaccine of those with no immunity to the disease (the *tuberculin test identifies which people require vaccination). The childhood immunization schedule no longer includes BCG vaccination at 10–14 years of age; vaccination now targets high-risk groups, such as immigrants from countries with a high incidence of TB. There has been a resurgence of tuberculosis in recent years in association with HIV infection. The number of patients with multidrug resistant TB has also increased due to patients not completing drug courses. Many centres have introduced directly observed therapy (DOT), in which nurse practitioners watch patients taking their drugs or administer the drugs.