What symptom is associated with active tuberculosis (TB)?

Cough, often productive and sometimes with blood, is a hallmark symptom of active tuberculosis (TB). This symptom arises because TB primarily affects the lungs, leading to inflammation and the destruction of lung tissue. The presence of a productive cough indicates that the body is attempting to clear the infection, and sputum may contain blood due to the erosion of blood vessels in the lung tissue caused by the disease. Other respiratory symptoms, such as chest pain and difficulty breathing, may also accompany this cough.

In contrast, sudden weight gain, persistent rash, and abdominal pain are not common symptoms specific to active TB. Sudden weight gain is typically not associated with TB; instead, patients frequently experience weight loss due to the energy depletion caused by the chronic infection. A persistent rash does not relate to TB either; this is more common in dermatological conditions or allergic reactions. Abdominal pain may occur in relation to extrapulmonary TB, but it is not a classic symptom of active pulmonary TB. Thus, the presence of a cough that is productive and possibly blood-streaked is the key indicator that aligns with the active phase of tuberculosis.