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Why can tuberculosis cause a person to cough up blood?
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tuberculosis
A doctor examining chest X-rays of patients infected with tuberculosis, which remains one of the world's deadliest diseases.
In pulmonary tuberculosis, the presence of blood in the sputum—a condition known as hemoptysis—occurs because of the physical damage caused by the disease within the lung.
As the infection progresses, it creates lesions consisting of collections of dead cells. These lesions can expand and erode into a neighboring bronchus or a nearby blood vessel. When a blood vessel is compromised in this manner, blood enters the airways and is subsequently expelled when the patient coughs.1