Pulmonary tuberculosis Health Article

Definition

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

Alternative Names

TB; Tuberculosis - pulmonary

Causes, incidence, and risk factors

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

In the United States, most people will recover from primary TB infection without further evidence of the disease. The infection may stay asleep or nonactive (dormant) for years and then 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, or antirejection medicines given after an organ transplant

Your risk of contracting TB increases if you:

• Are in frequent contact with people who have the disease
• 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 class.

See also: Disseminated tuberculosis

Symptoms

The primary stage of the disease usually doesn't have symptoms. When symptoms do occur, they may include:

• Cough (sometimes producing phlegm)
• 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
• 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