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Difference between pneumonia and tuberculosis

pneumonia and tuberculosis chest x rays

Tuberculosis and pneumonia are two distinct forms of lung infection that share some common signs and symptoms, which is why they can be confused.

In most cases, it is not difficult to distinguish between pneumonia and pulmonary tuberculosis. However, in elderly, diabetic patients, chronic renal insufficients, liver patients or patients with HIV, the clinical and radiological features of both pneumonia and tuberculosis may be atypical, making it difficult to establish a correct diagnosis.

The most common situation in which the correct distinction between pneumonia and tuberculosis becomes necessary is when the patient has a picture suggestive of pneumonia, with fever and cough, but does not respond adequately to the antibiotics commonly used to treat pneumonia. Pulmonary tuberculosis is therefore one of the main differential diagnoses of difficult-to-solve pneumonia.

In this article we will summarize the main clinical and radiological differences of tuberculosis in its pulmonary form and pneumonia. To learn more about tuberculosis and pneumonia, visit the links below:


Etiological agents

While pneumonia can be caused by several different bacteria, besides fungi or viruses, tuberculosis has a unique etiologic agent, which is Mycobacterium tuberculosis , a bacterium also known as Koch’s bacillus.

Bacterial pneumonia is usually caused by a bacterium called Streptococcus pneumoniae , but infections by Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa and several other bacteria are also very common.


While tuberculosis is a contagious disease that can be transmitted through close contact and requires isolation of the patient for a few days, pneumonia does not pass from person to person and there is no need to keep the infected patient away from his friends and family.

Tuberculosis is an airborne infection, mainly through droplets expelled during the cough or while the patient speaks. Close contact is necessary for the transmission of the bacillus. Relatives and people working in the same environment are the most contagious contagious contacts.

Pneumonia, on the other hand, is caused by the aspiration of bacteria usually present in the oropharynx. In normal situations, the immune system of the airways can neutralize those bacteria that come from the mouth, keeping the lungs free of germs. However, because of a variety of factors, such as reduced immunity, smoking, stress, lack of adequate sleep, presence of other diseases, contact with more virulent bacteria than usual, etc., airway defenses can fail and invasive bacteria can lead to the development of a lung infection.

Disease time

An essential difference between pneumonia and tuberculosis is the time of evolution of both. Pneumonia is an acute, rapidly progressive infection. Within a few hours, the patient’s clinical condition worsens and he or she feels the need to seek medical attention. In general, the interval between the onset of the first symptoms and the demand for medical care is 48 to 72 hours.

Sometimes pneumonia is preceded by an influenza picture. The patient has a common cold and a few days later he noticed a sudden worsening of the condition, worsening of general condition, shortness of breath and coughing with expiration.

In tuberculosis evolution is different. The symptoms appear slowly and gradually. The patient notes weight loss and progressive decline in general condition. The fever usually starts low and is rising. The same thing happens with the cough, which gets worse with time. Weeks may pass until the patient decides to seek medical help.

Signals and symptons

The most common symptoms of pneumonia are fever, which is typically high, above 38.5 ° C, and cough with yellow or greenish expectoration. Thoracic pain is also common, especially deep breathing, tiredness, and shortness of breath. The patient usually has a general deteriorated state, with tachycardia (increased heart rate) and tachypnea (rapid breathing).

In the elderly, however, the picture may be atypical, more drawn, and without the usual symptoms. Even fever and coughing may not be evident.

Tuberculosis, on the other hand, usually presents a moderate fever, between 37,5ºC and 38,5ºC, of ??predominance afternoon (higher in the afternoon). Sweating and night chills are also common. The patient usually presents with progressive fatigue, loss of appetite and weight loss.

Coughing with sputum is common and, after a few days of illness, the sputum can become bloody.

Radiological findings

In pneumonia, chest X-rays usually show infiltrates or condensations. The typical image is a homogeneous or heterogeneous white spot at the base of the affected lung or the middle third. Pleural effusion on the same side is a common finding .

Tuberculosis usually causes cavitation at the apex of the lung, which provides a rounded image with air inside. Pleural effusion is also possible to be found.

Obviously, the radiological image is not always as clear as in the examples below.

pneumonia and tuberculosis chest x rays
First x-ray image shows tuberculosis and second image shows pneumonia


Response to treatment

When treated with appropriate antibiotics, pneumonia usually shows signs of improvement within the first 48 hours. In some patients, it is possible to notice clinical improvement in 24 hours. The treatment usually lasts only 8 days and the patient in 3 or 4 days is already completely free of symptoms.

Tuberculosis is an infection that takes longer to respond. The feeling of improvement takes a few days to appear and the fever may disappear only after 15 days. The recovery is slower and the treatment time is much longer, lasting at least 6 months.