Tuberculosis (TB) is a serious infectious disease caused by mycobacteria from the group of Mycobacterium tuberculosis.
Tuberculosis can affect any organ, but pulmonary tuberculosis is the most common form.
This condition can lead to death if not treated in time.
The bacteria that cause tuberculosis can spread from the lungs to other areas of the body via:
- Lymphatic fluid.
- Asia (especially India and South-East Asia),
- South America (especially Peru, Bolivia and Brazil),
- Central and Southern Africa.
It is estimated that one-third of all humanity is infected by the tubercle bacillus, and therefore tuberculosis will probably never die out; it has existed for as long as man has existed.
Development of tuberculosis (pathophysiology)
The tubercle bacillus has characteristic properties:
- cell wall rich in lipids and wax,
- long reproduction times (every 20 hours),
- alcohol- and acid-resistant,
- delayed hypersensitivity reaction (immune response of the body) that causes the symptoms.
In addition, the most commonly used antibiotics are not effective against the tubercle bacillus.
The mycobacterium enters the body and settles in the alveoli.
The macrophages (scavenger cells that absorb bacteria and cell residues) are the first cells to intervene:
- In people with a good immune system, a natural defense reaction (of macrophages and neutrophils) may occur. The mycobacterium is eliminated and the patient experiences spontaneous healing.
- In most cases (in immunocompetent people), the limitation phenomenon is noticeable: the bacterium remains latent or inactive, but can be activated when the immune system is weakened.
- In patients with compromised immune system (rarely occurs, for example, in AIDS patients), there are no defenses and infectious tuberculosis occurs directly.
The granuloma is cheese-forming, that is, it has a central necrosis, which is limited by:
- mononuclear cells,
- epithelioid giant cells,
The tubercle (nodular tumor) is a structure in which the tuberculous inflammation is contained. Here, the bacterium can live for an unlimited period of time, even throughout life.
The disease becomes active when the body’s defense system is weakened, for example:
- chronic diseases,
- Chemotherapy, etc.
Necrosis and granuloma formation
Classification into two phases:
The neutrophils and macrophages perform ineffective phagocytosis of the bacterium. The consequences are:
- cell destruction,
- Release of proteases (enzymes that break down proteins): hydrolases, collagenases and elastases.
The proteins of the mycobacterium are processed into peptides.
These are taken up by the dendritic cells that present the antigen to the lymphocytes, i.e. they expose foreign substances to some cells of the immune system in order to trigger defensive reactions.
After that, the lymphocyte becomes the most important cell because it ensures the release of cytokines (messenger substances):
- Interferon-y (IFN-y) – promotes scarring,
- MIF (inhibition factor of macrophage migration),
- Tumor necrosis factor α (TNF-α) – stimulates cell death (apoptosis).
Evolution of granuloma
Possible developments in the tubercle:
- fibrosis or formation of scar tissue,
- limescale deposits,
- liquefaction, the contents emerge and form:
- fistulas (formation of an abnormal canal between two organs or cavities),
Latent and active tuberculosis
Not all people who inhale these bacteria develop tuberculosis. In healthy people, the immune system fights the bacteria and prevents them from multiplying.
Nevertheless, these bacteria can remain in a dormant or latent state in the body.
A tuberculin skin test or a Mendel-Mantoux test will show whether a person has been exposed to tuberculosis bacteria.
If the test is positive and the patient shows no symptoms, the diagnosis is a latent tuberculous infection.
People with latent tuberculosis infection cannot infect other people, but the infection can develop and become active.
The disease manifests itself with the typical symptoms.
Causes of active tuberculosis
The cause is exposure to the bacterium Mycobacterium tuberculosis (tubercle bacillus).
The risk factors in developed countries are:
- gastric removal (gastrectomy),
- silicosis or exposure to particulate matter containing a lot of silicon,
- psychiatric illnesses,
- stay in overcrowded prisons,
- Workplace in a crèche
- workplace in a hospital,
- Immunosuppressive therapy.
In malnutrition, the infection occurs more frequently, including mental anorexia (anorexia).
Immunocompromised people (for example, those suffering from AIDS) are more easily infected than healthy people.
Pulmonary tuberculosis originates in the lungs and spreads to other areas of the body.
The characteristic symptoms of active pulmonary tuberculosis are:
- Cough that lasts at least 3 weeks (with or without blood and phlegm)
- Chest pain
- Unexplained weight loss
- Night sweats
- Loss of appetite
Phases of tuberculosis
Primary pulmonary tuberculosis
Occurs mainly in children, but can also occur in adults.
This is the initial phase of the disease, in which:
- an inflammatory reaction develops in the alveoli,
- the lymph nodes swell.
The germ causes a mild flu, which passes unnoticed, only a calcification of the lung tissue remains.
The chest X-ray shows the primary complex, that is, the granuloma.
In healthy people, the immune system fights the bacteria and prevents the progression of the disease.
However, sometimes the immune system cannot completely eliminate the bacteria.
Only in a few cases does an obvious disease occur.
Secondary pulmonary tuberculosis (reactivation)
Reactivation of a previous subclinical infection can occur when the immune system is weakened.
This may be the case in people whose immunodeficiency is caused by:
- HIV infection
- severe stress
- Alcohol and drug addiction
As a rule, the upper lobes of the lung are affected.
Spontaneous healing is impossible.
Complications of pulmonary tuberculosis
Progressive pulmonary tuberculosis
Although primary and secondary tuberculosis can be treated, immunocompromised individuals may develop a:
- tuberculous pneumonia,
- miliary tuberculosis (form of disseminated tuberculosis),
- Cavitary tuberculosis (formation of cavities due to the decomposition of pulmonary and bronchial vessels).
Tuberculous pneumonia is a complication of tuberculosis characterized by a progressive lung infection.
Particularly at risk are:
- persons with a weak or damaged immune system,
Common symptoms include:
Miliary tuberculosis or disseminated tuberculosis
A characteristic sign is the appearance of small granulomas (nodes) in the lungs.
The infection can spread to the rest of the body and nodules can form in other tissues and organs of the body, such as:
- high fever,
- gradual weight loss,
- Deterioration of the state of health.
The microbacteria can cause significant damage to the upper lobes of the lung (tip of the lung) by forming large cavities.
The infection extends into the pleural space and increases the risk of complications, such as pleural effusion.
Extrapulmonary TB exists when the infection affects other organs. Examples are:
- bone and osteoarticular tuberculosis;
- ocular tuberculosis;
- pleural tuberculosis, if the pleura is affected;
- lymph node tuberculosis – the most common form of extrapulmonary tuberculosis, which mainly attacks the neck and mandibular lymph nodes;
- meningeal tuberculosis, if the meninges are affected;
- Gastrointestinal tuberculosis – the infection affects the intestinal mucosa (rarely found in industrialized countries);
- peritoneal tuberculosis – affects the membrane that protects the abdominal organs;
- pericardial tuberculosis – the infection attacks the pericardium;
- skin tuberculosis (rare);
- Hepatic tuberculosis (can cause a tubercular abscess in the liver)
- Genital tuberculosis – in women, tuberculosis can attack the fallopian tube, in men the prostate and testicles;
- Renal or bladder tuberculosis.
Extrapulmonary TB is not contagious because it is not possible to transmit the bacterium by air.
However, sometimes individuals with extrapulmonary TB also suffer from pulmonary tuberculosis.
In these circumstances, the infection can be transmitted to other people through direct personal contact.
Extrapulmonary tuberculosis is more common in people with immunodeficiency.
Symptoms of tuberculosis
The first contact with the bacterium can be confused with a simple flu. In healthy people, the disease does not develop after first contact or primary inflammation.
Symptoms occur with reactivation of the infection or post-primary infection.
The incubation period is between 15 days and about 3 months.
- persistent cough with sputum or blood,
- weakness and fatigue,
- high fever,
- night sweats,
- loss of appetite,
- weight loss,
- chest pain,
- dyspnea or shortness of breath,
- pleurisy (inflammation of the pleura),
- enlarged lymph nodes,
- Joint pain and swelling.
Infected kidneys can cause:
An infection of the spine can lead to lumbar or back pain.
Children and patients with HIV infection can have very severe complications.
Is tuberculosis contagious? How is it transmitted?
The bacteria responsible can be transmitted to others by air if a person infected with pulmonary tuberculosis:
The transfer can take place via:
- the inhalation of these airborne infectious droplets,
- the use of objects belonging to an infected person.
All sorts of things can lead to contagion, for example:
- clothing and bed linen,
- Food, etc.
It is important to thoroughly wash items of an infected person and store them separately.
Adequate ventilation of the rooms is important, as tuberculosis spreads mainly in:
- enclosed spaces,
- poorly ventilated rooms.
Are the microbacteria:
- in the expectorate (sputum), the person is very infectious;
- in the secretory culture, the sick person is less contagious;
- not in the expectorate, the risk of infection is insignificant.
If a patient is undergoing treatment and has a low bacterial count, he cannot infect other people.
The transmission occurs when the TBC is “open”. This applies if the affected lung area extends to the bronchi and thus receives contact with the outside.
Since the disease is highly contagious, it is not advisable to visit a person suffering from TB.
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