A 22-year-old man with AIDS complains of persistent cough, night sweats, low-grade fever and general malaise. A chest X-ray reveals an area of consolidation in the periphery of the left upper lobe, as well as hilar lymphadenopathy. Sputum cultures show acid-fast bacilli. Which of the following is the most likely diagnosis?
A 22-year-old man with AIDS complains of persistent cough, night sweats, low-grade fever and general malaise. A chest X-ray reveals an area of consolidation in the periphery of the left upper lobe, as well as hilar lymphadenopathy. Sputum cultures show acid-fast bacilli. Which of the following is the most likely diagnosis?
💡 Explanation
## **Core Concept**
The patient's symptoms and chest X-ray findings suggest a diagnosis of tuberculosis (TB), particularly given the presence of acid-fast bacilli in sputum cultures. TB is a bacterial infection caused by *Mycobacterium tuberculosis*, commonly affecting the lungs but can spread to other parts of the body. It is especially prevalent in immunocompromised individuals, such as those with AIDS.
## **Why the Correct Answer is Right**
The combination of persistent cough, night sweats, low-grade fever, general malaise, and the radiographic findings of an area of consolidation in the periphery of the left upper lobe along with hilar lymphadenopathy are classic for pulmonary tuberculosis. The presence of acid-fast bacilli in sputum cultures is diagnostic of TB, as *Mycobacterium tuberculosis* is an acid-fast bacillus. In immunocompromised patients, such as those with AIDS, TB can present atypically and progress rapidly.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, incorrect options might include other causes of pneumonia (e.g., *Streptococcus pneumoniae*, *Haemophilus influenzae*) or different mycobacterial infections. These would not typically present with this constellation of symptoms and acid-fast bacilli in sputum.
- **Option B:** Similarly, without the specific text, one might guess this could be another infectious agent or condition. However, given the context, any option not directly related to *Mycobacterium tuberculosis* or closely related mycobacteria would be incorrect.
- **Option C:** This would also be incorrect for similar reasons as Option A, assuming it does not align with the diagnosis of tuberculosis or a closely related condition.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in patients with AIDS, TB can have an atypical presentation, and the tuberculin skin test (TST) may be falsely negative due to anergy. Therefore, a high index of suspicion and early diagnosis are crucial. Additionally, the treatment of TB involves a combination of antibiotics (typically isoniazid, rifampicin, pyrazinamide, and ethambutol) for at least 6 months.