What is Primary Lung Tuberculosis?
Tuberculosis, also known as TB, was discovered in 1882 by Robert Koch. It’s one of the oldest known diseases and it’s a serious global health issue causing a large number of deaths worldwide. TB is unique to humans; animals don’t naturally get it.
Remarkably, Tuberculosis is the number one killer when it comes to diseases caused by a single infectious agent. It’s especially deadly for people with HIV/AIDS. About a third of the entire world’s population have been infected with the bacteria that causes tuberculosis, called Mycobacterium tuberculosis. Each year sees around ten million new cases globally. TB affects a considerable portion of the global population, about 24%, with significant social and economic impacts.
The main damage caused by TB involves the formation of specific types of inflammation that can destroy tissues, primarily within the lungs in 87% of cases. However, it is important to know that TB can affect practically any organ in the body. It is most common in people who live in crowded conditions, those who have migrated from countries where tuberculosis is common, people with weakened immune systems such as those with HIV, and healthcare workers.
While the number of TB cases worldwide has been slowly reducing, it’s still a common issue, particularly in places like Sub-Saharan Africa. It’s still a major cause of death, with an estimated 1.5 million people dying from it annually. One of the main long-term effects of lung-based Tuberculosis is reduced lung function. This article will give an overview of lung tuberculosis, focusing on the main aspects of the disease.
What Causes Primary Lung Tuberculosis?
There are many different types of Mycobacterium, a kind of bacteria, that have varying structures, shapes, and preferred environments. More than 170 kinds have been identified. One such type is Mycobacterium tuberculosis, which causes tuberculosis. This bacterium does not move, prefers oxygenated areas, and is actually quite small. What sets it apart is its complex wall, packed full of long-chain fatty acids.
There are two main groups within the Mycobacterium genus – those that grow quickly, and those that grow slowly. M. tuberculosis falls into the slower-growing group. Its cell wall is abundant in a substance called peptidoglycan and complex lipids, both of which play big roles in the bacteria’s ability to cause disease. It’s also covered by an outer layer, or capsule, which significantly contributes to its ability to cause harm and survive in harsh conditions.
M. tuberculosis is quite sneaky; it can live inside the cells in our bodies that are meant to destroy bacteria, called macrophages. Inside these cells, the bacteria can reproduce and eventually cause the macrophage to die, providing it a route out to the lungs’ air sacs.
Scientists use special dyes, such as Ziehl-Neelsen stain, to spot these bacteria under a microscope because they resist the standard staining techniques, hence the term acid-fast. Despite its many survival tactics, M. tuberculosis is slow to grow, taking up to a full day to do so.
Risk Factors and Frequency for Primary Lung Tuberculosis
Tuberculosis, or TB, is a disease that is closely monitored in almost all countries. This helps to keep an accurate track of this disease’s occurrence and aids in various studies. Previously, the occurrence of TB was on a steady decline, but the rise of HIV infection led to an increase again. As it stands, tuberculosis is now a top reason for illness and death worldwide. Research estimates that around 1.7 billion people have been infected with TB. It was responsible for around 2.5% of all deaths globally in 2004.
In 2017, around 10 million people worldwide got infected with TB, according to the World Health Organization. India and China see the highest numbers of TB deaths. The disease primarily affects countries with high poverty rates, with about 183 cases per 100,000 people. In contrast, developed nations have less than ten cases per 100,000 people. Despite these numbers, the global occurrence of TB is slowly declining by about 1.6% each year. Among HIV patients, TB is the primary cause of death.
- Certain medical conditions and medications like diabetes, chronic corticosteroid use, and anti-TNF biologics increase the risk of developing TB.
- Patients who have had a gastrectomy surgery are also at risk, likely due to specific nutritional deficiencies.
- Rare genetic defects affecting gamma interferon, IL-12, and IL-23 signaling pathways can result in a more severe form of the disease.
Tuberculosis spreads through tiny droplets in the air that an infected person releases when they cough, sing, shout, or sneeze. Higher risk of transmission happens when you’re exposed for a long time, such as in households or workplaces. Other familiar places for TB spread include prisons, mines, and public transport. People with a positive smear test result are considered highly infectious. Moreover, if the disease has caused cavities to form in the lungs, it can lead to increased spreading as the bacteria can move more easily.
Children under the age of 5 and people with HIV have a higher chance of catching the disease.
Signs and Symptoms of Primary Lung Tuberculosis
After the initial infection, most individuals do not experience any symptoms and are also able to clear the infection. Nonetheless, some people enter a “dormant” phase where the infection doesn’t cause any problems but has the potential to “reactivate” in the future. Approximately 10 percent of patients who do show signs of the disease develop a lung infection. Some of these patients experience the spread of infection to different parts of the body, mainly if their immune systems are compromised, like in people living with HIV.
Persistent fever is the most commonly reported symptom, even though only one third of individuals with lung involvement have respiratory symptoms. This fever usually increases during the day and subsides at night, sometimes accompanied by night sweats. Pulmonary symptoms can include chest discomfort, shortness of breath, and cough, which can be mild and non-productive. But, as the disease progresses, the cough may bring up green or blood-tinged sputum. In severe cases, individuals might experience loss of appetite, weight loss, muscle mass loss, and other signs such as swollen lymph nodes, fatigue, and a sore throat.
A peculiar aspect of tuberculosis infection is latency. A significant number of people who get infected actually do not develop symptoms until several months to years after their initial exposure, which is known as latent tuberculosis. Current research suggests that during this stage, the bacterium might enter a no-growth state. Reactivation of the tuberculosis infection takes a long time that could sometimes take years to progress. The symptoms are quite similar to the primary disease and typically include fever, cough, shortness of breath, and weight loss.
Mild cases of the disease usually show normal or nonspecific lung findings like crackles or tubular breath sounds during a physical examination. Areas with consolidated infection may exhibit absent breath sounds. Physical signs of disease spread to other organs might also be seen.
Testing for Primary Lung Tuberculosis
If you have been coughing for more than three weeks as well as experiencing other symptoms such as fever, night sweats, spitting up blood, or weight loss, your doctor might suspect that you have tuberculosis (TB), a serious lung infection. This suspicion may also arise if you’re in a group more likely to get TB — such as due to living in a low-income area, struggling with a chronic illness like diabetes or kidney disease, dealing with a weakened immune system (such as in HIV-positive individuals), or using IV drugs.
The first stage in figuring out if you have TB is typically a chest x-ray. If the x-ray shows signs of the disease, the next step usually involves collecting and testing three samples of mucus you’ve coughed up. The samples undergo a special staining process to see if they contain “acid-fast bacilli” (AFB), which are the germs causing TB. In addition, one sample is examined with a technique called “nucleic acid amplification” (NAAT), which can identify the TB bacteria’s genetic material.
If both AFB culture and NAAT tests come back positive, it’s quite likely that you have TB, and your doctor will usualy start treatment. To further support the diagnosis, your doctor may also order a tuberculin skin test (TST) or an interferon-gamma release assay (IGRA). These tests measure your body’s immune response to TB bacteria, but note that a negative result on these tests doesn’t necessarily mean you don’t have TB.
In the cases where test results aren’t clear, additional steps might be needed such as a bronchoscopy (a procedure where a thin tube with a camera on the end is inserted into your lungs to take a sample), or a lung biopsy (a procedure to remove a small piece of lung tissue for examination).
In the early stages of TB, chest x-rays usually appear normal. However, as the disease progresses, enlargement of lymph nodes near your lungs (referred to as “hilar lymphadenopathy”) is a typical finding. Other common signs include shadowy spots near the center and upper right side of your lungs, and accumulation of fluid around your lungs (called “pleural effusion”).
Treatment Options for Primary Lung Tuberculosis
In 2016, various organizations in the United States and around the world, including the American Thoracic Society and the Center for Disease Control and Prevention (CDC), joined forces to create global guidelines for treating tuberculosis that can be destroyed by drugs. Tuberculosis is caused by a bacteria and the aim of the treatment is to kill this bacteria, prevent it from returning and to hinder its ability to resist drug treatment.
Treatment of active tuberculosis follows a two-step procedure: an intense phase, which lasts for two months, followed by a continuation phase lasting at least four months. The common drugs used in the intensive phase include isoniazid, rifampin, pyrazinamide and ethambutol. These drugs attempt to aggressively target the bacteria and halt its spread. For the continuation phase, doctors usually recommend isoniazid and rifampin. These drugs are designed to complete the job of eradicating the bacteria from the patient’s body. Ideally, the patient takes these drugs under direct observation known as Directly Observed Therapy (DOT) to make sure they are taken correctly for best results. Regular tests (monthly, until two consecutive tests come back negative) are done during this treatment to keep track of the progress.
The standard approach of treatment includes taking isoniazid, rifampin, pyrazinamide and ethambutol for about 8 weeks, followed by isoniazid and rifampin for around 18 weeks. This ensures that the bacteria causing tuberculosis are completely removed from the body. Certain patients like those who are pregnant, breastfeeding babies, diabetic, suffering from chronic kidney disease, alcoholics, older individuals, and those living with HIV need to also receive vitamin B6 supplements as they are at risk of nerve damage.
Treating tuberculosis in patients who are infected with HIV is a unique challenge because of potential drug interaction with antiretroviral therapy. It is typically recommended to follow the same anti-tuberculosis treatment schedule for such patients, unless they are not receiving antiretroviral therapy. In those cases, treatment may need to be extended.
In some situations, where the tuberculosis infection is latent (not active or causing symptoms), fewer medications are needed and for a shorter period of time. Latent tuberculosis treatment usually includes isoniazid and/or rifampin for various periods of time, depending on the patient’s specific circumstances.
However, as with any medication, these drug treatments may have side effects such as nausea, vomiting, skin rashes or damage to the liver or nerves. It’s important to monitor the patient’s health regularly during treatment to identify and manage any side effects.
Tuberculosis bacteria can also develop resistance to the drugs used in the treatment, making it more challenging to treat effectively. The types of drug-resistant tuberculosis are categorized based on the drugs the bacteria is resistant to. For cases where the bacteria is resistant, alternative drugs are employed to combat the infection, however, the success rates tend to be lower than standard drug treatment. Treatment of drug-resistant tuberculosis is typically longer than the normal course and involves monitoring the patient’s response to the alternative drug regimen.
What else can Primary Lung Tuberculosis be?
When diagnosing a patient with respiratory symptoms, it can be difficult because the cause could be any number of things. However, doctors do consider a list of common conditions that could be responsible:
- Sarcoidosis: This is a disease that’s usually identified by the presence of a certain type of tissue swelling known as non-caseating granuloma, and it’s how doctors can tell it apart from tuberculosis.
- Fungal infections: This can include things like Histoplasmosis, Aspergillosis, Actinomycosis, Blastomycosis, and Nocardiosis. Knowing your background and where you’ve lived can help doctors determine if you might have picked up these infections.
- Nontuberculous mycobacterial infections (NTM): An example of this type of infection would be a bacterium called Mycobacterium kansasii.
- Lung cancer or lymphoma: If your doctor thinks a tumor could be causing your symptoms, they’ll need to take a small sample of the tissue (a biopsy) to check under a microscope.
- Lung abscess: This is a pus-filled cavity in the lung.
While this isn’t an exhaustive list, these are some of the more common causes that doctors would consider when working to diagnose your symptoms.
What to expect with Primary Lung Tuberculosis
The progression and outcome of tuberculosis (TB) can vary greatly as it can affect more than one system in your body and is influenced by several factors. Your age, immune system strength, presence of other diseases, when treatment started, and whether you follow the treatment faithfully can all significantly influence the outcome. Generally speaking, treatment is successful for about 85% of people who have TB. According to the World Health Organization, the death rate from TB is estimated to be around 15%.
Possible Complications When Diagnosed with Primary Lung Tuberculosis
Tuberculosis affecting the lungs can lead to multiple complications. Bleeding can occur from airway-related blood vessels and between the ribs, resulting to coughing up blood. However, this usually involves a small amount of blood and rarely causes severe blood loss. If a tuberculosis infection breaks through the lining of the lung, or a lung cavity, it can result in a collapsed lung – a condition known as spontaneous pneumothorax. Swollen lymph nodes due to tuberculosis can place pressure on the air passages in the lungs and lead to a condition called bronchiectasis, which is the abnormal widening of these air passages. If left untreated, extreme lung destruction, tissue death, and serious infection of the lungs can occur. Additionally, it has been noted that tuberculosis can increase the risk of lung cancer. Less common complications include a fungal lung infection known as chronic pulmonary aspergillosis and severe full-body inflammatory response known as septic shock.
Complications of Pulmonary Tuberculosis:
- Bleeding leading to coughing up blood
- Collapsed lung due to infection breaking through lung lining
- Bronchiectasis due to pressure from swollen lymph nodes
- Extensive lung destruction, tissue death, and severe lung infection if left untreated
- Increase in risk of lung cancer
- Chronic pulmonary aspergillosis – a fungal lung infection
- Septic shock – a severe full-body inflammatory response
Preventing Primary Lung Tuberculosis
The most effective method to prevent the spread of tuberculosis (an infectious disease that mainly affects the lungs) involves identifying individuals who have the disease and giving them effective treatment. This approach significantly reduces the transmission of bacteria, which are what cause the tuberculosis, within groups of people. There is also a vaccine for tuberculosis, called the BCG vaccine, which has been used for a long time all around the world. This vaccine is typically given at birth or during infancy, especially in developing countries. While the BCG vaccine can help reduce the incidence of tuberculosis in children, it doesn’t seem to significantly affect the incidence in adults.
One specific approach that appears effective at reducing tuberculosis transmission in hospital settings is the FAST approach. This strategy involves finding unidentified cases of tuberculosis through fast molecular testing (a quick and accurate method to detect the bacteria), isolating these individuals safely, and initiating proper treatment.
Identifying areas with high tuberculosis rates (“hot spots”) and providing preventative therapy using a drug called INH can help reduce the spread of the disease within communities. Additionally, improving socioeconomic conditions, such as enhancing public transportation or improving general nutrition in a community, can help reduce crowded living conditions and the number of cases of close or prolonged contact between people. Ultimately, these changes can reduce the risk of tuberculosis transmission and decrease how much the disease affects a community.
Many potential vaccines have shown to be effective in animal models when compared to the older BCG vaccine. However, so far none have demonstrated efficacy in humans. For example, a trial involving a vaccine made using the vaccinia virus to prompt an immune response against M. tuberculosis (the bacteria that causes tuberculosis) failed to create a sufficient immune response in humans.
