Which finding is most suggestive of active pulmonary tuberculosis?

• A. Acute fever with rash
• B. Cough for at least 3 weeks with night sweats, weight loss, and cavitations on CXR
• C. Chronic bronchitis symptoms without fever
• D. No symptoms but positive PPD

Answer: (B)

The key idea is recognizing the combination of a prolonged respiratory illness with systemic symptoms and a radiographic sign that points to active infection. A cough lasting several weeks, along with night sweats and weight loss, reflects ongoing bacterial activity and the body's reaction to Mycobacterium tuberculosis. Cavitary lesions in the upper lobes on chest X-ray are classic for reactivation TB, where the infection is actively multiplying and the bacteria are concentrating in areas with high oxygen tension; cavitation signals substantial, contagious disease.

In contrast, a scenario with only fever and rash suggests another illness, chronic bronchitis without fever points away from TB, and a positive PPD without symptoms indicates latent TB rather than active disease.