Pulmonary tuberculosis

Definition

Pulmonary tuberculosis (TB) is a contagious bacterial infection that involves the lungs, but may spread to other organs.

Alternative Names

TB; Tuberculosis - pulmonary

Causes, incidence, and risk factors

Pulmonary tuberculosis (TB) is caused by the bacteria Mycobacterium tuberculosis (M. tuberculosis). You can get TB by breathing in air droplets from a cough or sneeze of an infected person. This is called primary TB.

In the United States, most people will recover from primary TB infection without further evidence of the disease. The infection may stay asleep or inactive (dormant) for years. However, in some people it can reactivate.

Most people who develop symptoms of a TB infection first became infected in the past. However, in some cases, the disease may become active within weeks after the primary infection.

The following people are at higher risk for active TB:

• Elderly
• Infants
• People with weakened immune systems, for example due to AIDS, chemotherapy, diabetes, or certain medications

Your risk of contracting TB increases if you:

• Are in frequent contact with people who have TB
• Have poor nutrition
• Live in crowded or unsanitary living conditions

The following factors may increase the rate of TB infection in a population:

• Increase in HIV infections
• Increase in number of homeless people (poor environment and nutrition)
• The appearance of drug-resistant strains of TB

In the United States, there are approximately 10 cases of TB per 100,000 people. However, rates vary dramatically by area of residence and socioeconomic status.

See also: Disseminated tuberculosis

Symptoms

The primary stage of TB usually doesn't cause symptoms. When symptoms of pulmonary TB occur, they may include:

• Cough (usually cough up mucus)
• Coughing up blood
• Excessive sweating, especially at night
• Fatigue
• Fever
• Unintentional weight loss

Other symptoms that may occur with this disease:

• Breathing difficulty
• Chest pain
• Wheezing

Signs and tests

Examination may show:

• Clubbing of the fingers or toes (in people with advanced disease)
• Enlarged or tender lymph nodes in the neck or other areas
• Fluid around a lung (pleural effusion)
• Unusual breath sounds (crackles)

Tests may include:

• Biopsy of the affected tissue (rare)
• Bronchoscopy
• Chest CT scan
• Chest x-ray
• Interferon-gamma blood test such as the QFT-Gold test to test for TB infection
• Sputum examination and cultures
• Thoracentesis
• Tuberculin skin test

Treatment

The goal of treatment is to cure the infection with drugs that fight the TB bacteria. Treatment of active pulmonary TB will always involve a combination of many drugs (usually four drugs). All of the drugs are continued until lab tests show which medicines work best.

The most commonly used drugs include:

• Isoniazid
• Rifampin
• Pyrazinamide
• Ethambutol

Other drugs that may be used to treat TB include:

• Amikacin
• Ethionamide
• Moxifloxacin
• Para-aminosalicylic acid
• Streptomycin

You may need to take many different pills at different times of the day for 6 months or longer. It is very important that you take the pills the way your health care provider instructed.

When people do not take their TB medications as recommended, the infection becomes much more difficult to treat. The TB bacteria may become resistant to treatment, and sometimes, the drugs no longer help treat the infection.

When there is a concern that a patient may not take all the medication as directed, a health care provider may need to watch the person take the prescribed drugs. This is called directly observed therapy. In this case, drugs may be given 2 or 3 times per week, as prescribed by a doctor.

You may need to be admitted to a hospital for 2 - 4 weeks to avoid spreading the disease to others until you are no longer contagious.

Your doctor or nurse is required by law to report your TB illness to the local health department. Your health care team will be sure that you receive the best care for your TB.

Support Groups

You can ease the stress of illness by joining a support group where members share common experiences and problems.

See: Lung disease - support group

Expectations (prognosis)

Symptoms often improve in 2 - 3 weeks. A chest x-ray will not show this improvement until later. The outlook is excellent if pulmonary TB is diagnosed early and treatment is begun quickly.

Complications

Pulmonary TB can cause permanent lung damage if not treated early.

Medicines used to treat TB may cause side effects, including liver problems. Other side effects include:

• Changes in vision
• Orange- or brown-colored tears and urine
• Rash

A vision test may be done before treatment so your doctor can monitor any changes in your eyes' health over time.

Calling your health care provider

Call your health care provider if:

• You have been exposed to TB
• You develop symptoms of TB
• Your symptoms continue despite treatment
• New symptoms develop

Prevention

TB is a preventable disease, even in those who have been exposed to an infected person. Skin testing (PPD) for TB is used in high risk populations or in people who may have been exposed to TB, such as health care workers.

A positive skin test indicates TB exposure and an inactive infection. Discuss preventive therapy with your doctor. People who have been exposed to TB should be skin tested immediately and have a follow-up test at a later date, if the first test is negative.

Prompt treatment is extremely important in controlling the spread of TB from those who have active TB disease to those who have never been infected with TB.

Some countries with a high incidence of TB give people a BCG vaccination to prevent TB. However, the effectiveness of this vaccine is controversial and it is not routinely used in the United States.

People who have had BCG may still be skin tested for TB. Discuss the test results (if positive) with your doctor.

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References

Iseman MD. Tuberculosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 345.

Fitzgerald DW, Sterling TR, Haas DW. Mycobacterium tuberculosis. In: Mandell GL, Bennett JE, Dolan R, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 7th ed. Orlando, FL: Saunders Elsevier; 2009:chap 250.