Which disease is caused by Mycobacterium tuberculosis, with the lungs usually involved, but any organ may be affected?

• A. Tuberculosis (TB)
• B. URI
• C. Laryngitis
• D. Legionnaire's Disease

Answer: (A)

Tuberculosis is caused by Mycobacterium tuberculosis. It usually involves the lungs, but the bacteria can spread through the bloodstream and lymphatic system, so any organ can be affected, leading to extrapulmonary TB. This wide potential for involvement sets TB apart from other infections that stay confined to a single site. Transmission occurs via inhaled airborne droplets from an infected person, and the disease often presents with a chronic cough, fever, night sweats, and weight loss. Understanding that the same organism can inhabit the lungs and also lodge in other tissues helps explain why TB is described as primarily pulmonary with possible systemic involvement.