**Core Concept**
When treating a patient with both HIV and tuberculosis (TB), it is essential to consider the interactions between the two diseases and the potential for overlapping or conflicting treatment regimens. The goal is to initiate therapy that effectively addresses both conditions while minimizing the risk of adverse effects.

**Why the Correct Answer is Right**
The correct approach is to start with antitubercular therapy (ATT) first, followed by antiretroviral therapy (A) for HIV. This is because TB treatment is typically initiated immediately to prevent the spread of TB and to reduce the risk of mortality. ATT is usually given for at least 2 months before starting A, as concurrent administration can lead to increased toxicity and decreased efficacy. The most common ATT regimen includes a combination of rifampicin, isoniazid, pyrazinamide, and ethambutol. Once ATT is initiated, A can be started, and the patient can be switched to a combination of antiretroviral drugs, such as tenofovir, emtricitabine, and efavirenz.

**Why Each Wrong Option is Incorrect**
**Option A:** Starting both ATT and A simultaneously can lead to increased toxicity, particularly with regards to liver function, as rifampicin can induce the metabolism of antiretroviral drugs, reducing their efficacy.

**Option C:** Initiating ATT alone without considering the patient's HIV status may not be sufficient to control the HIV infection, potentially leading to viral resistance and treatment failure.

**Option D:** Starting A first and then ATT can allow TB to progress, leading to increased morbidity and mortality. This approach also increases the risk of TB transmission to others.

**Clinical Pearl / High-Yield Fact**
In patients with HIV and TB, it is essential to perform an HIV resistance test before starting antiretroviral therapy to guide the selection of an optimal treatment regimen.

✓ Correct Answer: B. First ATT and then A.