2.22 Tuberculosis

Pulmonary system review for the USMLE Step 1 Exam

• Tuberculosis is caused by Mycobacterium tuberculosis bacteria and mainly affects the lungs. It is more common in developing countries, with India, Indonesia, China, Nigeria, Pakistan, and South Africa having the most TB deaths worldwide.

• TB is spread through inhaling infected aerosolized droplets, making crowded places hotspots for TB spread.

• Primary TB infection occurs when a person inhales infected droplets and the bacteria become dormant in a granuloma. Secondary TB infection occurs when the bacteria disseminate to surrounding tissues, affecting various parts of the body.

• Symptoms of active TB include night sweats, weight loss, fever, and cough (sometimes with blood). TB can present with various symptoms, making it known as the "great imitator."

• Diagnosis methods include chest X-rays, sputum acid-fast staining, and real-time nucleic acid amplification. Chest X-rays showing cavitary lesions and positive acid-fast staining are indicative of TB.

• Treatment involves a 4-drug combination of rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE) for an extended period of time (2-4 months) to get rid of the infection.