Pulmonary tuberculosis. X-ray of the chest of a patient after recovery from pulmonary tuberculosis (TB). Damaged areas of the lungs (small white patches) have hardened due to calcium deposition. Pulmonary tuberculosis is caused by the bacterium Mycobacterium tuberculosis, spread by coughing and sneezing. The bacterium grows into a primary tubercle (nodular lesion) when inhaled into the lungs, and often spreads to nearby lymph nodes. Pulmonary tuberculosis may be symptomless, and may recur at periods when the patient's immune system is weakened. Symptoms of the active disease include fever, weight loss and the coughing up of blood. Treatment is with long-term antibiotics.