The Link Between Tuberculosis and Chronic Respiratory Diseases Explained
The Link Between Tuberculosis and Chronic Respiratory Disease.
Chronic respiratory diseases are a major cause of disability and death across the world. However, the contribution of pulmonary tuberculosis as a causative factor of chronic respiratory disease is often ignored.

In many cases, pulmonary tuberculosis is found to cause chronic respiratory diseases such as COPD, pulmonary fibrosis & restrictive lung diseases. This correlation holds greater value in geographical areas where the number of tuberculosis patients is high. A previous history of being diagnosed with or treated for pulmonary tuberculosis (TB) is a major contributory risk factor for long-term respiratory diseases. Many times, the respiratory dysfunction after tuberculosis goes undetected even if it is frequent and is often related to poor quality of life. Therefore, patients with tuberculosis or a history of treated tuberculosis should be aware of these possibilities and consult their physician for periodic observations and precautionary measures.

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About Tuberculosis (TB)

Tuberculosis (TB) is a highly infectious respiratory disease. It is caused by a bacterium called Mycobacterium tuberculosis, which settles and grows in the lungs when breathed in. Usually, the lungs get affected by tuberculosis but other parts of the body, like the spine, kidneys and even the brain may get affected. If not treated early, tuberculosis may acquire a serious form and may disseminate to other parts of the body

Tuberculosis & Respiratory diseases

Patients who have been treated for tuberculosis seem to substantially contribute to the rising numbers of Chronic Obstructive Pulmonary Disease (COPD) worldwide.

It is seen that patients who had pulmonary tuberculosis in the past are at a greater risk for developing long-term impairment or weakness of the respiratory system. Sometimes dysfunction after tuberculosis treatment may remain unrecognized for a long time and is associated with a reduced quality of life. However, factors which cause lung impairment after tuberculosis still remain unclear. It is believed that the body’s immune response against long-standing inflammation caused by tuberculosis probably plays a dominant role in lung damage.

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Tuberculosis can be treated effectively, however, it is observed that despite adequate treatment, nearly half of the people who have survived active tuberculosis may still suffer from some sort of persistent dysfunction of the lungs even after the bacteria have been eliminated completely. Pulmonary dysfunction which essentially means some sort of respiratory disease or disability may range from minor abnormalities of the lung to those causing severe breathlessness. It is estimated that a severe post-tuberculosis pulmonary dysfunction can even increase the risk for death-from-respiratory-causes.

The Process of TB Infection

Tuberculosis is a contagious disease which means that the tuberculosis bacteria spread from one person to another. This happens through small, microscopic droplets released into the air when an untreated individual who has an active form of tuberculosis speaks, coughs, sneezes, and spits in proximity with a non-infected individual.

Presence of tuberculosis germs in the body without the presence of sickness or ability to spread due to protection by the immune system is called latent tuberculosis. Majority of the individuals with tuberculosis have latent TB. Even though the bacteria in latent tuberculosis may not be growing, a person can get sick any time. This is why immediate treatment is recommended even if a person has an inactive TB infection.

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Effects of TB on the body

Tuberculosis bacteria are countered by the immune cells of the body. In people with a weakened or underdeveloped immune system, for example ailments like HIV/AIDS, patients on chemotherapy, children below five years of age are at a higher risk of developing TB disease. Upon breathing in, the TB bacteria start settling within the lungs and multiply aggressively as the body’s immune system is inadequate to fight the bacteria in such cases. TB disease can develop quickly within a period of days or weeks after infecting the immunocompromised person.

In healthy individuals, latent tuberculosis may not show any signs and symptoms of the disease for months or even years. However, in situations when the immune system becomes weak like chronic diseases of the respiratory tract, fever, etc. render them unable to fight the Mycobacteria. In the case of active TB disease, the bacteria start multiplying rapidly and begin to attack the lungs or parts of the body like the spine, kidney, the lymph nodes, bones, brain. etc. Clumps of TB bacteria travel from the lungs via the blood or lymphatic system to various body parts. Some of the symptoms associated with the active disease include persistent cough, weight loss, loss of appetite, low grade persistent fever, chills, and night sweats.

In addition to the above mentioned, symptoms pertaining to the loss of function of the specific organ or system may also be seen. As an example, in case the lungs are affected, the individual may cough up blood or sputum and TB of bones may be associated with bone pain.

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Seriousness of Tuberculosis

TB can cause cough, pain and mucus with blood on coughing in many cases. If not treated early, the disease may progress to complications that can be fatal. TB is still a very significant challenge and a threat to public health across the world. It is estimated that roughly one-third or 2.5 billion people across the world may be infected with tuberculosis. In a majority of cases, the affected people may have latent TB. However, nearly 9.6 million people worldwide may be living with active TB disease. The World Health Organization (WHO) estimates that tuberculosis is one of the top 10 reasons for death worldwide. Nearly 1.7 million people died of the disease in 2016. Despite being such a serious disease, tuberculosis can be prevented and cured under the right conditions, if adequate precautions are taken and timely treatment is started.

Chronic Obstructive Pulmonary Disease (COPD)

Chronic Obstructive Pulmonary Disease (COPD) is a chronic (long-lasting) respiratory disease which is characterized by a chronic obstruction to the flow of air within the respiratory tract. It is believed to be the third most common cause of deaths worldwide, more so in the low and middle-income countries. It is suggested that infectious diseases like tuberculosis have a role to play in COPD. Pulmonary tuberculosis is the leading cause of mortality due to respiratory infection worldwide. There is enough evidence that geographical regions which show a high number of tuberculosis cases, also report a high number of cases and deaths due to COPD.

Does tuberculosis cause chronic obstructive pulmonary disease (COPD)?

It is known that tuberculosis increases the risk of chronic obstructive pulmonary disease (COPD) manifolds. Even if a person has been treated for tuberculosis and survived it, the risk of developing chronic obstructive pulmonary disease persists. Another issue is that owing to ignorance, COPD remains greatly underdiagnosed, more so if a person is a non-smoker.

Also read: Researchers develop novel strategy for tuberculosis vaccine

Common risk factors between tuberculosis and COPD

Chronic obstructive pulmonary disease and tuberculosis share certain common risk factors like personal history of smoking tobacco, low socioeconomic status and compromised immune defense.

A person with tuberculosis, especially the elderly, have an increased risk for chronic obstructive pulmonary disease. However, even though there are other medical conditions like HIV/AIDS, diabetes, cancers, etc. which increase the risk of acquiring tuberculosis, the causative effect of chronic obstructive pulmonary disease on tuberculosis and subsequent death is yet to be established strongly.

Association between restrictive lung diseases & Tuberculosis

The healing process within the lung during and after treatment of tuberculosis can cause scarring, in turn, causing the loss of parenchymal tissue (the spongy part of the lung) ultimately leading to restrictive spirometry or restrictive lung disease. The lungs fail to fully expand to their fuller extent in restrictive lung disease, limiting the volume of oxygen inhaled & exhaled in comparison to a person with normal lungs. To compensate for this change and meet the demand of oxygen, the person’s rate of breathing often becomes faster. In most of the cases, restrictive lung diseases are progressive in nature, which means they worsen over time.

Also read: Saline Nasal Wash And Its Role in Upper Respiratory Diseases

Relationship between pulmonary fibrosis & tuberculosis

Damage and scarring of the lung tissues leads to a condition called pulmonary fibrosis. The lungs are rendered ineffective in functioning properly due to the thickening and stiffening of the lung tissue. A person may experience progressive shortness of breath with worsening of pulmonary fibrosis. Pulmonary fibrosis is usually not a primary disease and may occur secondary to other respiratory diseases or interstitial lung diseases. Tuberculosis is one such disease which causes fibrotic changes in the upper or lower lobes of the lungs and microscopic injuries to the lung. Other diseases which cause pulmonary fibrosis include chronic viral and bacterial infections, autoimmune disorders, etc. which lead to long standing immune response and inflammation. Some of the commonly reported symptoms of pulmonary fibrosis are exertion induced shortness of breath, persistent dry cough, fatigue and weakness, discomfort or pain in the chest, loss of appetite, unintended rapid weight loss.

Association Between Tuberculosis & Bronchiectasis

In many patients with pulmonary tuberculosis, a complication or sequel called bronchiectasis may be reported. Bronchiectasis is a respiratory condition in which the walls of the air tubes of the lung called bronchi thicken due to long-term inflammation and infection resulting in irreversible dilatation of bronchi due to loss of elasticity of bronchial walls. Male patients with lower body mass index and history of tuberculosis are more likely to have bronchiectasis. The history of severe shortness of breath is longer in case of patients with TB bronchiectasis as compared to patients with TB alone. Sometimes, a rarer case of bronchiectasis known as dry bronchiectasis presents in the form of episodic blood-tinged sputum or haemoptysis. Dry bronchiectasis if present is associated with tuberculosis and affects the upper lobes of the lungs. Bronchiectasis is more of a microscopic structural diagnosis hence it may not present with very obvious symptoms. Some other causes of bronchiectasis are bacterial and pneumonia viral infections like measles, pertussis, aspergillosis, congenital cystic fibrosis, secondary to chemotherapy, etc.

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Chronic respiratory diseases are a major cause of disability and death across the world and so is tuberculosis. However, the contribution of pulmonary tuberculosis as a causative factor of chronic respiratory disease is often ignored. It is believed that the immune response of the body probably plays an important role in damage to the lung structures due to excessive inflammation during TB. For anyone with a history of pulmonary tuberculosis, consult a Pulmonologist and be regular for follow up care, also follow the recommendations and precautionary measures necessary.

Contributed by Dr. Viswesvaran Balasubramanian, Consultant Interventional Pulmonology and Sleep Medicine, Yashoda Hospitals, Hyderabad.

This post first appeared on The Health Site

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