A 41-year-old man is admitted with severe shoness of breath. He complains of a 25-lb weight loss over the last 2 mo and occasional vomiting after meals. On physical examination, vital signs are: pulse 110 bpm; temperature 98degF; respirations 24/min; blood pressure 110/70 mm Hg. Peinent findings: dullness to percussion on the left posterior chest with decreased breath sounds. A patchy area of egophony is heard over the left upper lung field posteriorly. PPD is 15 mm. CXR is shown in. The most likely diagnosis is

**Core Concept**
The patient presents with symptoms of weight loss, night sweats, and a positive PPD, indicating a possible infection with Mycobacterium tuberculosis. The physical examination findings of dullness to percussion, decreased breath sounds, and egophony over the left upper lung field posteriorly suggest a lung lesion.

**Why the Correct Answer is Right**
The patient's symptoms and physical examination findings are consistent with a diagnosis of pulmonary tuberculosis (TB). The presence of a lung lesion with associated symptoms such as weight loss and night sweats is a classic presentation of TB. The positive PPD result further supports this diagnosis, as it indicates exposure to M. tuberculosis. The CXR findings are also consistent with pulmonary TB, showing a cavity or consolidation in the left upper lung field.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not take into account the patient's symptoms of weight loss and night sweats, which are classic for TB. While a lung abscess can present with cough and fever, it typically does not cause weight loss or night sweats.

**Option B:** This option is incorrect because it does not consider the patient's positive PPD result, which indicates exposure to M. tuberculosis. While lung cancer can present with a lung mass, it is not typically associated with a positive PPD result.

**Option C:** This option is incorrect because it does not account for the patient's symptoms of weight loss and night sweats. While pneumonia can present with cough and fever, it typically does not cause weight loss or night sweats.

**Option D:** This option is incorrect because it does not consider the patient's positive PPD result, which indicates exposure to M. tuberculosis. While sarcoidosis can present with lung nodules, it is not typically associated with a positive PPD result.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a lung lesion, it is essential to consider the patient's symptoms, physical examination findings, and laboratory results, including the PPD result, to determine the most likely diagnosis. A positive PPD result is a strong indicator of exposure to M. tuberculosis and should prompt further evaluation for pulmonary TB.

**Correct Answer:** C. Pulmonary tuberculosis.

✓ Correct Answer: C. Pleural effusion