Primary TB most commonly involves ?

Since tuberculosis is most commonly transmittead through aerosoles from an open case of TB, lung is most commonly involved in primary TB. Secondary TB may present as extra pulmonary TB and can be seen in lymph nodes, intestine, brain etc through dissemination through blood and lymph Pulmonary TB is caused by the bacterium Mycobacterium tuberculosis (M tuberculosis). You can get TB by breathing in air droplets from a cough or sneeze of an infected person. The resulting lung infection is called primary TB In pulmonary tuberculosis, most commonly repoed symptom is chronic cough. Cough most of the times is productive, sometimes mixed with blood. Constitutional symptoms like fever, weight loss, lymphadenopathy, and night sweats are common. Ref Harrison20th edition pg 1079