**Core Concept**
Clofazimine is an anti-tubercular drug used in multidrug-resistant tuberculosis (MDR-TB) treatment. It acts by disrupting mycobacterial cell membranes and has significant tissue penetration, leading to various adverse effects, particularly in the skin and gastrointestinal tract.

**Why the Correct Answer is Right**
Clofazimine is well known for causing **skin staining** (due to its lipophilic nature and accumulation in skin), **icthyosis** (a dry, scaly skin condition resembling ichthyosis), and gastrointestinal disturbances such as **diarrhoea**. However, **gastritis** is not a well-documented or clinically significant adverse effect of clofazimine. The drug does not directly irritate gastric mucosa or inhibit gastric acid secretion, unlike drugs such as NSAIDs or alcohol. Thus, gastritis is not a recognized or common side effect.

**Why Each Wrong Option is Incorrect**
Option A: Skin staining is a hallmark effect of clofazimine due to its accumulation in skin and keratinocytes.
Option B: Icthyosis occurs due to impaired skin barrier function and is frequently reported in patients on long-term clofazimine therapy.
Option C: Diarrhoea is a known gastrointestinal side effect, possibly due to local irritation or disruption of intestinal flora.
Option D: Gastritis is **not** a recognized adverse effect of clofazimine; no clinical or pharmacological evidence supports this.

**Clinical Pearl / High-Yield Fact**
Clofazimine is notorious for causing **permanent skin discoloration** and **dry, scaly skin**—a key adverse effect to remember in TB patients on long-term therapy. Always consider skin changes when evaluating patients on clofazimine.

✓ Correct Answer: D. Gastritis