Doctor's Notes on Tuberculosis
Tuberculosis (TB) is an infectious disease caused by bacteria. Initial infections usually have no symptoms in people or, if people do develop symptoms, the symptoms are nonspecific such as fever and an occasional dry cough. However, as the disease progresses slowly, symptoms such as weight loss, loss of energy, fever, a productive cough, poor appetite and night sweats may develop. The disease may go dormant for years, but when it returns, symptoms may include a cough that produces increased mucus, the patient may cough up blood and the symptoms of fever, loss of appetite, weight loss and night sweats return. Some patients develop infection in the lungs that spreads into the pleural space which causes chest pain. Other patients develop tuberculosis in other organs such as lymph nodes, bones and/or joints, meninges, the genitourinary tract and the outside lining of the gastrointestinal tract. Symptoms of pain and discomfort can be associated with the location of the infection and may produce symptoms like those described above.
Tuberculosis is caused by a rod-shaped bacterium, Mycobacterium tuberculosis. The bacteria are transmitted person-to-person by inhaled droplets that contain the bacteria. In the lungs, the body’s macrophage engulfs the bacteria. Sometimes the macrophages cannot kill the bacteria and then the bacteria can be transported via the lymph system or blood inside a macrophage to other body organs. Occasionally, the bacteria go dormant (latent TB infection) then reactivate so that the bacteria multiply and thus reactivate tuberculosis symptoms.
You may not notice any symptoms of illness until the disease is quite advanced. Even then the
- Only about 10% of people infected with M. tuberculosis ever develop tuberculosis disease. Many of those who suffer TB do so in the first few years following infection. However, the bacillus may lie dormant in the body for decades.
- Although most initial infections have no symptoms and people overcome them, they may develop fever, dry cough, and abnormalities that may be seen on a chest X-ray.
- This is called primary pulmonary tuberculosis.
- Pulmonary tuberculosis frequently goes away by itself, but in more than half of cases, the disease can return.
- Tuberculous pleuritis may occur in some people who have the lung disease from tuberculosis.
- The pleural disease occurs from the rupture of a diseased area into the pleural space, the space between the lung and the lining of the chest and abdominal cavities. This is often quite painful since all of the pain fibers of the lung are located in the pleura.
- These people have a nonproductive cough, chest pain, and fever. The disease may go away and then come back at a later date.
- In a minority of people with weakened immune systems, TB bacteria may spread through their blood to various parts of the body.
- This is called miliary tuberculosis and produces fever, weakness, loss of appetite, and weight loss.
- Cough and difficulty breathing are less common.
- Generally, return of dormant tuberculosis infection occurs in the upper lungs. Symptoms include
- Some people may develop tuberculosis in an organ other than their lungs. About a quarter of these people usually had known TB with inadequate treatment. The most common sites include the following:
- lymph nodes,
- genitourinary tract,
- bone and joint sites,
- meninges, and
- the lining covering the outside of the gastrointestinal tract.
All cases of TB are passed from person to person via droplets. When someone with TB infection coughs, sneezes, or talks, tiny droplets of saliva or mucus are expelled into the air, which can be inhaled by another person.
- Once infectious particles reach the alveoli (small saclike structures in the air spaces in the lungs), another cell, called the macrophage, engulfs the TB bacteria.
- Then the bacteria are transmitted to the lymphatic system and bloodstream and spread to other organs occurs.
- The bacteria further multiply in organs that have high oxygen pressures, such as the upper lobes of the lungs, the kidneys, bone marrow, and
meninges -- themembrane-like coverings of the brain and spinal cord.
- When the bacteria cause clinically detectable disease, you have TB.
- People who have inhaled the TB bacteria, but in whom the disease is controlled, are referred to as infected. Their immune system has walled off the organism in an inflammatory focus known as a granuloma. They have no symptoms, frequently have a positive skin test for TB, yet cannot transmit the disease to others. This is referred to as latent tuberculosis infection or LTBI.
- Risk factors for TB include the following:
Bacteria are microscopic, single-cell organisms that live almost everywhere. Bacteria live in every climate and location on earth. Some are airborne while others live in water or soil. Bacteria live on and inside plants, animals, and people. The word "bacteria" has a negative connotation, but bacteria actually perform many vital functions for organisms and in the environment. For example, plants need bacteria in the soil in order to grow.
The vast majority of bacteria are harmless to people and some strains are even beneficial. In the human gastrointestinal tract, good bacteria aid in digestion and produce vitamins. They also help with immunity, making the body less hospitable to bad bacteria and other harmful pathogens. When considering all the strains of bacteria that exist, relatively few are capable of making people sick.
COPD (Chronic Obstructive Pulmonary Disease) QuizQuestion
COPD (chronic obstructive pulmonary disease) is the same as adult-onset asthma.See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.