What is tuberculosis?
Mycobacterium tuberculosis infects more than 2 billion people. The leading risk factors for tuberculosis (TB) are poverty, HIV infection, and drug resistance. It is initially a lung disease that goes on to involve the bronchial tree, lymph nodes, and can even result in spread to distant sites. Late-stage disease involves destruction of lung tissue. TB is 2-3 times more frequent in older adults and immunocompromise increases the risk of being affected.
Primary TB: new TB infection in someone who has never had it. The most frequent symptom is fever (most common) and pleuritic/retrosternal pain (25%). On X-ray can be seen enlargement of lymph nodes in the hilar regions of the lungs in 65%, pleural effusions in 1/3, and pulmonary infiltrates (27%).
When a person ingests aerosol droplets from a person with TB, either:
- The organism is cleared
- The organism causes primary TB
- The patient develops latent infection
- A previous latent disease can become reactivated
Normal immunity causes 90% of infections to go into a “latent” phase. 10% progress to pneumonia and progressive infiltrates. Meningitis, pericarditis, or distant seeding can occur.
Reactivation TB: reactivation of a prior TB infection. Symptoms begin 2-3 years or longer after primary infection and include a low-grade fever, a cough, weight loss, fatigue, fever, night sweats, chest pain, and dyspnea.
Endobronchial TB: TB of the tracheobronchial tree. This results in difficulty breathing and distortion of the bronchi and bronchioles.
Complications of TB
Complications include coughing up blood (hemoptysis), pneumothorax from ruptured subpleural necrosis, bronchiectasis, progressive destruction of lung, septic shock, and increased risk of lung cancer and chronic pulmonary fungal aspergillosis.