Causes of Tuberculosis

List of causes of Tuberculosis

Following is a list of causes or underlying conditions (see also Misdiagnosis of underlying causes of Tuberculosis) that could possibly cause Tuberculosis includes:

• AIDS
• Immunodeficiency
• Pneumoconiosis - in coal mine workers
• Malnutrition
• Alcoholism

Tuberculosis as a complication of other conditions:

Other conditions that might have Tuberculosis as a complication may, potentially, be an underlying cause of Tuberculosis. Our database lists the following as having Tuberculosis as a complication of that condition:

• Latent tuberculosis
• Peripheral uveitis
• Silicosis
• Whooping Cough

Tuberculosis as a symptom:

Conditions listing Tuberculosis as a symptom may also be potential underlying causes of Tuberculosis. Our database lists the following as having Tuberculosis as a symptom of that condition:

• AIDS-Related Opportunistic Infections
• Bacillaceae Infections
• Exudative retinopathy familial, autosomal dominant
• Exudative retinopathy familial, autosomal recessive
• Exudative retinopathy familial, X-linked, recessive
• Exudative retinopathy, familial
• Exudative vitreoretinopathy 3
• Exudative vitreoretinopathy 4
• Type IV Hypersensitivity

What causes Tuberculosis?

Causes: Tuberculosis: Various mycobacterium classes such as Mycobacterium tuberculosis and Mycobacterium bovis.
Article excerpts about the causes of Tuberculosis:
Most people infected with M. tuberculosis never develop active TB. However, in people with weakened immune systems, especially those infected with the human immunodeficiency virus (HIV, the cause of AIDS), TB organisms may overcome the body's defenses, multiply, and cause active disease. Each year, 8 million people worldwide develop active TB and 3 million die. (Source: excerpt from Tuberculosis, NIAID Fact Sheet: NIAID)

Related information on causes of Tuberculosis:

As with all medical conditions, there may be many causal factors. Further relevant information on causes of Tuberculosis may be found in:

• Risk factors for Tuberculosis
• Contagiousness for Tuberculosis
• Genetics of Tuberculosis
• Hidden causes of Tuberculosis

Causes of Tuberculosis: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the causes of Tuberculosis.

Tuberculosis: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

After exposure to M. tuberculosis, roughly 5% of infected people develop active TB within 1 year; in the remainder, microorganisms cause a latent infection. The host’s immune system usually controls the tubercle bacillus by enclosing it in a tiny nodule (tubercle). The bacillus may lie dormant within the tubercle for years and later reactivate and spread.

Although the primary infection site is the lungs, mycobacteria commonly exist in other parts of the body. Several factors increase the risk of infection reactivation: gastrectomy, uncontrolled diabetes mellitus, Hodgkin’s disease, leukemia, silicosis, acquired immunodeficiency syndrome, treatment with corticosteroids or immunosuppressants, and advanced age.

Transmission is by droplet nuclei produced when infected persons cough or sneeze. Persons with a cavitary lesion are particularly infectious because their sputum usually contains 1 to 100 million bacilli per milliliter. If an inhaled tubercle bacillus settles in an alveolus, infection occurs, with alveolocapillary dilation and endothelial cell swelling. Alveolitis results, with replication of tubercle bacilli and influx of polymorphonuclear leukocytes. These organisms spread through the lymph system to the circulatory system and then through the body.

Cell-mediated immunity to the mycobacteria, which develops 3 to 6 weeks later, usually contains the infection and arrests the disease. If the infection reactivates, the body’s response characteristically leads to caseation — the conversion of necrotic tissue to a cheeselike material. The caseum may localize, undergo fibrosis, or excavate and form cavities, the walls of which are studded with multiplying tubercle bacilli. If this happens, infected caseous debris may spread throughout the lungs by the tracheobronchial tree. Sites of extrapulmonary TB include the pleurae, meninges, joints, lymph nodes, peritoneum, genitourinary tract, and bowel.

The incidence of TB has been increasing in the United States secondary to homelessness, drug abuse, and human immunodeficiency virus infection. Globally, TB is the leading infectious cause of morbidity and mortality, generating 8 to 10 million new cases each year.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Tuberculosis: Causes
(Handbook of Diseases)

After exposure to M. tuberculosis, roughly 5% of infected people develop active TB within 1 year; in the remainder, microorganisms cause a latent infection. The host’s immune system usually controls the tubercle bacillus by killing it or walling it up in a tiny nodule (tubercle). However, the bacillus may lie dormant within the tubercle for years and later reactivate and spread. Those at higher risk for disease progression or reactivation of dormant disease include infants, the elderly, and individuals who are immunocompromised (such as those with acquired immunodeficiency syndrome [AIDS], those undergoing chemotherapy, or transplant recipients taking antirejection medications).

A person’s risk of contracting TB increases if he has frequent contact with people who have the disease, if he lives in crowded or unsanitary living conditions, or if he has poor nutrition. There has been an increase of incidence of TB in the United States due to the increase of human immunodeficiency virus infection, the increasing number of homeless individuals (poor environment and poor nutrition), and the appearance of drug-resistant strains of TB.

Reactivation risk factors

Although the lungs are the primary infection site, mycobacteria commonly exist in other parts of the body. A number of factors increase the risk of infection reactivation: gastrectomy, uncontrolled diabetes mellitus, Hodgkin’s disease, leukemia, silicosis, AIDS, and treatment with corticosteroids or immunosuppressants.

Mode of transmission

TB is transmitted by droplet nuclei produced when infected persons cough or sneeze. After inhalation, if a tubercle bacillus settles in an alveolus, infection occurs. Cell-mediated immunity to the mycobacteria, which develops about 3 to 6 weeks later, usually contains the infection and arrests the disease.

Response to reactivation

If the infection reactivates, the body’s response characteristically leads to caseation — the conversion of necrotic tissue to a cheeselike material. The caseum may localize, undergo fibrosis, or excavate and form cavities, the walls of which are studded with multiplying tubercle bacilli. If this happens, infected caseous debris may spread throughout the lungs by the tracheobronchial tree.

Sites of extrapulmonary TB include pleura, meninges, joints, lymph nodes, peritoneum, genitourinary tract, and bowel.

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Source: Handbook of Diseases, 2003

Tuberculosis: Tuberculosis - etiology
(The 5-Minute Pediatric Consult)

Direct contact with a person with active TB through transmission of air-borne droplets

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Source: The 5-Minute Pediatric Consult, 2008

Pediatric Tuberculosis: Etiology
(Pediatric Infectious Disease)

Infection with Mycobacterium tuberculosis (MTB) begins with the inhalation of airborne bacilli. After inhalation, the bacilli reach the pulmonary alveoli and are transported through pulmonary lymphatic channels to hilar lymph nodes. They can then enter the bloodstream by way of the thoracic duct. Although the entrance of MTB into the host is respiratory, the organism can thus be spread to virtually every organ in the body. Spread of small numbers of bacilli result in clinically inapparent foci of infection. Regions most commonly seeded include the meninges, the pleura, and the bone. A reaction involving macrophages, lymphocytes, and ingested organisms then occurs, and tubercles are formed. When this reaction occurs, a tuberculin skin test will become positive, indicating that exposure to MTB has occurred.

The initial immune containment of clinically inapparent infection may not be permanent, and reactivation is possible at any time. Infants younger than 1 year of age have about a 50% chance of developing active disease. In children younger than 5 years of age, the risk for reactivation to active disease is about 25%.

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Source: Pediatric Infectious Disease, 2004