A man presents with fever, wt loss and cough; Mantoux reads an induration of 17 x 19 mm: Sputum cytology is negative for AFB. Most likely diagnosis is:
**Question:** A man presents with fever, wt loss and cough; Mantoux reads an induration of 17 x 19 mm: Sputum cytology is negative for AFB. Most likely diagnosis is:
A. Tuberculosis (TB)
B. Pneumonia
C. Bronchogenic carcinoma
D. Lung abscess
**Correct Answer:** A. Tuberculosis (TB)
**Core Concept:** Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, which primarily affects the lungs. The Mantoux test measures the immune response to the TB antigen, with larger indurations suggesting a stronger immune response and increased likelihood of TB infection. Negative sputum cytology for AFB (acid-fast bacilli) does not rule out TB, as the test might not detect TB in its early stages or in immunocompromised patients.
**Why the Correct Answer is Right:** A reading of 17 x 19 mm in the Mantoux test indicates a strong immune response, which is suggestive of an active TB infection. In this scenario, the patient presents with fever, weight loss, and cough, which are common symptoms of TB. Additionally, negative sputum cytology for AFB does not exclude TB, as mentioned above.
**Why Each Wrong Option is Incorrect:**
**A. Pneumonia:** Pneumonia is an infection of the lungs caused by various pathogens. While TB can cause pneumonia, the strong immune response in the Mantoux test and the presence of fever, weight loss, and cough are more suggestive of TB.
**B. Bronchogenic carcinoma:** This refers to cancer of the lung and can present with similar symptoms to TB. However, a strong immune response in the Mantoux test and the absence of AFB in sputum cytology are less indicative of bronchogenic carcinoma compared to TB.
**C. Lung abscess:** A lung abscess is a localized collection of pus within the lung, which can also present with symptoms mentioned but the strong immune response in the Mantoux test and the absence of AFB in sputum cytology are less indicative of lung abscess compared to TB.
**D. Lung abscess:** Similar to option C, a lung abscess presents with symptoms mentioned, but the strong immune response in the Mantoux test and the absence of AFB in sputum cytology are less indicative of lung abscess compared to TB.
**Clinical Pearls:**
**Why This is Important:** The strong immune response in the Mantoux test and the absence of AFB in sputum cytology are crucial clues pointing towards TB, despite the patient's symptoms being similar to other lung diseases. These tests are more sensitive in diagnosing TB than relying solely on clinical symptoms. Additionally, the patient's weight loss and cough are common symptoms of TB.
**Clinical Pearls:**
**Why This is Important:** The combination of strong immune response in the Mantoux test and negative AFB sputum smear result are crucial clues pointing towards TB, even if the patient's symptoms are similar to other lung diseases