pulmonary tuberculosis Pulmonary tuberculosis, also known as "pulmonary consumption," is a respiratory infectious disease caused by infection with Mycobacterium tuberculosis, with lesions primarily occurring in lung tissue, trachea, bronchi, and pleura.

Tuberculosis, also known as "pulmonary consumption," is a respiratory infectious disease caused by infection with Mycobacterium tuberculosis. The lesions primarily occur in lung tissue, trachea, bronchi, and pleura.

The main route of transmission for pulmonary tuberculosis is through respiratory droplet transmission. When a patient with pulmonary tuberculosis coughs, sneezes, laughs, talks, or sings, droplets containing Mycobacterium tuberculosis can be dispersed into the air from the respiratory tract and can remain suspended for several hours. If inhaled by others, it can lead to infection. Other rare transmission routes, such as infection through ingesting milk containing the bacteria, transmission from infected pregnant women to their babies via the placenta, infection through skin wounds, and direct inoculation into the upper respiratory tract, are now uncommon.

Infection of the human body with Mycobacterium tuberculosis is the basic cause of pulmonary tuberculosis. Healthy individuals inhaling droplets containing Mycobacterium tuberculosis may become infected, and this infection may further develop into pulmonary tuberculosis. Whether infection occurs and whether disease develops depend on factors such as the individual's immune system, the quantity and virulence of Mycobacterium tuberculosis, and other factors.

In general, after most people are infected with Mycobacterium tuberculosis, the immune system can eliminate the majority of the bacteria, but a small number of bacteria remain dormant in the body for a long period. At this stage, the infected individual does not show symptoms and is in a state of latent tuberculosis infection. A small proportion of people (including those susceptible to pulmonary tuberculosis) infected with Mycobacterium tuberculosis cannot effectively clear or suppress the bacteria by their immune system. As a result, the bacteria proliferate in the body, causing inflammation and other pathological changes, leading to clinical symptoms such as cough, sputum production, blood-tinged sputum, or hemoptysis. The condition may progress to active pulmonary tuberculosis.

Pulmonary tuberculosis generally has infectivity (except for tuberculous pleurisy). Patients with pulmonary tuberculosis (those with positive sputum smear results) are the main source of transmission of pulmonary tuberculosis in the population.

It is important to note that individuals infected with Mycobacterium tuberculosis do not necessarily transmit the infection to others. Individuals with latent tuberculosis infection generally do not have infectivity, but when the body's immune function is compromised, it can progress to active pulmonary tuberculosis, thus becoming infectious.

Patients with active pulmonary tuberculosis usually have strong infectivity, but after appropriate drug treatment for at least two weeks, the majority of patients become non-infectious.

Known risk factors associated with pulmonary tuberculosis include:

Age: Elderly people and infants are at increased risk of developing pulmonary tuberculosis.

Weakened immune system: Patients with conditions such as HIV infection, undergoing chemotherapy, and diabetes.

Close contact with tuberculosis-infected individuals.

Poor nutritional status.

Crowded living conditions.

Poor hygiene.

Occupation in the medical field: Doctors, nurses, social workers, or healthcare providers are at high risk for pulmonary tuberculosis.

Substance and alcohol abuse.

Travel to geographical areas where untreated pulmonary tuberculosis is common, such as parts of Latin America, Africa, Asia, and certain parts of Europe.

Chronic lung diseases.

Smoking.

Use of certain immunosuppressive drugs, such as steroids and infliximab.

Cough, sputum production for ≥2 weeks, blood-tinged sputum, or hemoptysis are suspicious symptoms of pulmonary tuberculosis.

Mycobacterium tuberculosis Latent Infection

There are no clinical symptoms of pulmonary tuberculosis, and there is no infectivity. Among the 2.5 billion people globally infected with Mycobacterium tuberculosis, the majority are latent infection carriers. However, individuals with latent tuberculosis infection may develop active pulmonary tuberculosis, with a lifetime risk of tuberculosis disease as high as 15%.

Non-active Pulmonary Tuberculosis

Patients may have no obvious symptoms and are only detected through chest imaging examinations.

Active Pulmonary Tuberculosis

Pulmonary tuberculosis often has an insidious onset. As the disease progresses, patients may experience symptoms such as cough, sputum production, blood-tinged sputum, or hemoptysis, and some patients may have recurrent upper respiratory tract infection symptoms.

For lesions occurring in the pleura, symptoms such as irritative cough, chest pain, and dyspnea may be present.

When the lesions occur in the trachea or bronchi, patients often experience persistent irritative cough. In cases where lymphatic fistulas form and rupture into the bronchi or bronchial stenosis occurs, wheezing or dyspnea may occur.

In children with pulmonary tuberculosis, delayed development may be observed. Primary pulmonary tuberculosis in children may cause symptoms such as wheezing due to enlargement of lymph nodes near the trachea or bronchi, or the formation of lymph node-bronchial fistulas.

Patients with pulmonary tuberculosis may also experience systemic symptoms such as night sweats, fatigue, intermittent or sustained low-grade fever in the afternoon, loss of appetite, weight loss, and in female patients, menstrual irregularities or amenorrhea. In some cases, the onset of the disease is abrupt, with moderate to high fever, and some may experience varying degrees of dyspnea.

Symptomatic Treatment

The general symptoms of pulmonary tuberculosis quickly disappear under appropriate chemotherapy and do not require special treatment.

Hemoptysis is a common symptom of pulmonary tuberculosis. For minor hemoptysis, comforting the patient, reducing tension, and bed rest are the main measures. Hemostatic agents such as aminocaproic acid, tranexamic acid, phenylbutazone, and carbachol can be used.

For massive hemoptysis, vasopressin can be used, but caution is needed as it is contraindicated in patients with hypertension, coronary atherosclerotic heart disease, heart failure, and pregnant women.

Bronchial artery embolization can be used for hemoptysis caused by bronchial artery rupture.

Corticosteroid Therapy

It is only used for patients with severe tuberculosis toxicity symptoms and must be used under the condition of effective anti-tuberculosis drug treatment.

The dosage used depends on the severity of the condition. Generally, prednisone is orally administered at a dose of 20 mg per day, administered once daily, for 1-2 weeks, followed by a weekly reduction of 5 mg. The duration of treatment is 4-8 weeks.

As carriers of Mycobacterium tuberculosis latent infection do not have infectivity, there are no special precautions in their daily lives.

For patients with active pulmonary tuberculosis, close contact with others should be avoided. Once they are no longer infectious after treatment, they can resume their normal lives.

Patients with pulmonary tuberculosis should take their medication as prescribed by their doctor and should also pay attention to the following daily matters:

When coughing or sneezing, patients with pulmonary tuberculosis should avoid close contact with others and cover their mouth and nose.

Spitting should not be done in public places; sputum should be spat into a covered sputum cup with disinfectant.

If spitting is not convenient, sputum can be spat into a disinfectant moist tissue or a sealed sputum bag.

It is advisable to avoid crowded public places, and if necessary, wear a mask.

Provide education on tuberculosis prevention, such as cough etiquette.

Avoid contact with tuberculosis patients, especially in enclosed and crowded environments. If contact is unavoidable, appropriate respiratory protective equipment, such as masks, can be used.

For individuals at high risk of tuberculosis or those with a history of close contact with tuberculosis patients, perform a tuberculin skin test to detect tuberculosis patients early.

Vaccination and preventive chemotherapy also play an important role in preventing tuberculosis.

Vaccination:

A recent trial published in the New England Journal of Medicine showed that revaccination with Bacille Calmette-Guérin (BCG) had an efficacy of 45.4%, effectively reducing persistent Mycobacterium tuberculosis infection in adolescents. Another trial showed that the M72/AS01E vaccine had an efficacy of 54%, effectively preventing progression from latent tuberculosis infection to active pulmonary tuberculosis in HIV-negative adults, potentially offering new options for tuberculosis prevention.

BCG vaccination has a good effect in preventing tuberculous meningitis and miliary tuberculosis, which commonly occur in children. After BCG vaccination in newborns, measures to isolate them from tuberculosis patients should still be taken.

Preventive chemotherapy:

Mainly applied to high-risk populations susceptible to Mycobacterium tuberculosis infection, including HIV-infected individuals, close contacts of smear-positive pulmonary tuberculosis patients, untreated pulmonary fibrotic lesions (non-active), silicosis, diabetes, long-term users of corticosteroids or immunosuppressants, drug users, malnourished individuals, and children and adolescents with a tuberculin skin test induration ≥15 mm.

Commonly used isoniazid 300 mg/day for 6-9 months, with a single daily dose, or rifampicin and isoniazid, taken once daily for 3 months; or rifapentine and isoniazid taken three times weekly for 3 months. Recent studies have found that a regimen of isoniazid and rifapentine taken together once weekly for a total of 12 doses (3 months) has similar efficacy, but more validation is needed.