Differences between Pneumonia and Tuberculosis

Tuberculosis and pneumonia are two distinct forms of lung infection sharing some signs and symptoms in common, why can lead to misdiagnosis.

Pneumonia and tuberculosis lungs
Pneumonia and tuberculosis lungs

In most cases, it is not difficult to distinguish between pneumonia and pulmonary tuberculosis. However, in elderly patients, diabetics, patients with chronic kidney failure, liver disease or HIV patients, the clinical and radiological features of both pneumonia as 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 is needed is when the patient has a suggestive of pneumonia, with fever and cough, but does not respond appropriately to antibiotics commonly used to treat pneumonia. Pulmonary tuberculosis is therefore one of the main differential diagnosis of pneumonia difficult to solve.

Etiologic agents

While pneumonia can be caused by many different bacteria, and fungi, or viruses, tuberculosis has a single etiologic agent, which is the Mycobacterium tuberculosis, a known bacterium also as Koch's bacillus.

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


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

Tuberculosis is an airborne infection, mainly through droplets expelled during coughing or while the patient speaks. A close contact is necessary so that there is transmission of the bacillus. Family and people working in the same environment are the contactees at higher risk of infection.

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

Disease duration

An essential difference between pneumonia and tuberculosis is the time evolution of both. Pneumocystis infection is an acute, rapidly progressive. In a few hours, the patient's condition worsens and it feels the need to seek medical attention. In general, the interval between the onset of the first symptoms and health care demand is 48 to 72 hours.

Sometimes pneumonia is preceded by a flu-like frame. The patient has a common cold and some days after notice a sudden worsening of the picture, with worsening of the general state of breathlessness and cough with expectoration.

Tuberculosis evolution is different. The symptoms are emerging slowly and gradually. The patient notes and progressive weight loss poor general condition. Fever often low and will rising. The same occurs with the cough that worsens over time. Weeks may pass before the patient decides to seek medical assistance.

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 sputum. Also common are chest pain, especially with deep breathing, fatigue and shortness of breath. The patient usually lies with deteriorated general condition, 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, in turn, usually has a moderate fever between 37.5°C and 38.5°C, the evening predominance (highest in the late afternoon). Sweating and night chills are also common. The patient usually has progressive tiredness, loss of appetite and weight loss.

Productive cough is common and, after a few days of illness, the sputum may become bloody.

Radiological findings

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

Tuberculosis often cause cavitation in 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.

Response to treatment

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

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

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