Risk factors for active tuberculosis among persons who have been infected with tubercle bacilli
**Core Concept**
Tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis (M. tuberculosis). The risk of developing active TB disease among individuals with latent TB infection depends on various factors. These factors can be categorized into host-related, environmental, and immunological variables.
**Why the Correct Answer is Right**
The correct answer is associated with a significant increase in the risk of progressing from latent TB infection to active TB disease. This is because individuals with HIV infection have compromised cellular immunity, making it difficult for their bodies to contain the M. tuberculosis infection. The impaired immune response allows the bacteria to multiply and cause active TB disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Malnutrition is a risk factor for active TB, but it is not as significant as HIV infection in increasing the risk of progression from latent to active TB.
**Option B:** Smoking is a risk factor for various respiratory diseases, but it is not directly associated with the progression from latent to active TB.
**Option C:** Age is a risk factor for active TB, as older adults are more likely to develop TB disease. However, it is not as significant as HIV infection in increasing the risk of progression from latent to active TB.
**Clinical Pearl / High-Yield Fact**
Individuals with HIV infection should be screened for latent TB infection and treated promptly to prevent the progression to active TB disease.
**Correct Answer:** D. HIV infection.