Okay, let's tackle this question. The user wants me to explain which anti-TB drug causes Stevens-Johnson Syndrome (SJS). The correct answer is probably one of the common drugs like INH, RIF, or maybe EMB. Wait, I remember that SJS is a severe skin reaction, often drug-induced. Let me recall which drugs are associated with it.

Hmm, from what I've studied, sulfonamides and pyrazinamide are known for causing SJS. Also, some anticonvulsants like carbamazepine. But among the anti-TB drugs, pyrazinamide (PZA) is a big one. Oh right, and ethambutol? Wait, no, ethambutol's main side effect is optic neuritis. I think PZA is more likely here. So the correct answer would be pyrazinamide.

Now, the options weren't provided, but let's assume the options are standard anti-TB drugs. Let's say option C is pyrazinamide. Then, the correct answer would be C.

Why is pyrazinamide the right choice? Because it's a known cause of hypersensitivity reactions, including SJS. The mechanism involves immune-mediated hypersensitivity. Other drugs like INH can cause liver toxicity, and RIF can cause flu-like symptoms. Ethambutol causes optic neuropathy. So the other options are incorrect because they don't cause SJS.

Clinical pearl: Remember that SJS is a severe reaction with a high mortality rate. It's important to recognize early signs like rash, fever, and mucosal involvement. If a patient on TB treatment develops these symptoms, PZA should be considered a culprit.

Let me structure this into the required sections. Make sure each part is concise. Core concept is about drug-induced hypersensitivity. Then explain why PZA is correct, then each wrong option. Then the clinical pearl. Finally, the correct answer line.

**Core Concept**
Stevens-Johnson Syndrome (SJS) is a severe immune-mediated hypersensitivity reaction, often drug-induced, characterized by skin and mucosal blistering. Anti-TB drugs like **pyrazinamide** are classic culprits due to their association with hypersensitivity pathways.

**Why the Correct Answer is Right**
Pyrazinamide (PZA) is a well-documented cause of SJS in TB treatment. Its mechanism involves activation of T-cell-mediated hypersensitivity, leading to keratinocyte apoptosis via cytokine release (e.g., TNF-α). PZA’s structural similarity to sulfonamides may also contribute to cross-reactivity in hypersensitive individuals.

**Why Each Wrong Option is Incorrect**
**Option A (Isoniazid):** Primarily causes hepatotoxicity and peripheral neuropathy, not SJS.
**Option B (Rifampicin):** Known for inducing drug-induced hepatitis and red-orange body fluids, not SJS.
**Option D (Ethambutol):** Causes optic neuritis and visual disturbances, unrelated to SJS.

**Clinical Pearl / High-Yield Fact**
**Remember:** SJS is a medical emergency with high morbidity. In TB patients, discontinue **pyrazinamide** immediately if SJS is suspected. Cross-reactivity with sulfonamides is a red flag—avoid both in

✓ Correct Answer: B. Thioacetazone