Okay, let's tackle this question about Lichen planus. The question is asking which statement is NOT true. First, I need to recall the key features of Lichen planus.

Lichen planus is a chronic inflammatory condition that affects the skin and mucous membranes. It's characterized by pruritic, polygonal, violaceous papules. The oral mucosa is commonly involved, which is a key point. So any answer that contradicts this involvement would be incorrect.

The correct answer here is probably an option that states something false about the condition. For example, if an option says it's a bacterial infection, that's wrong because it's an immune-mediated condition. Another common misconception is that it's contagious, which it's not. Also, the histopathology shows a band-like lymphocytic infiltrate in the dermis, so if an option mentions a different type of infiltrate, that's incorrect.

I need to check each option against known facts. Let's say the options are: A. It is a viral infection, B. It can affect the oral mucosa, C. It presents with Wickham's striae, D. It is associated with lichen planus pigmentosus.

Option A would be incorrect because Lichen planus is not viral. Option B is correct. Option C is correct as Wickham's striae are a hallmark. Option D is correct because lichen planus pigmentosus is a variant. So the correct answer would be A.

Now, structuring the explanation with the required sections. Make sure to cover the core concept, explain why the correct answer is right, address each wrong option, and include a clinical pearl. Keep it concise and within the character limit.

**Core Concept**
Lichen planus is a T-cell-mediated inflammatory disorder affecting skin and mucous membranes. It presents with pruritic, polygonal, violaceous papules and is characterized histologically by a band-like lymphocytic infiltrate and "civatte bodies." Oral involvement is common, and Wickham’s striae (reticular white lines) are pathognomonic.

**Why the Correct Answer is Right**
If the correct answer states a false claim (e.g., "Lichen planus is caused by a bacterial infection"), it is incorrect because the condition is **immune-mediated**, not infectious. Its pathogenesis involves CD8+ T cells targeting epithelial basal cells, leading to apoptosis and the classic histopathologic features. No microbial agent is implicated.

**Why Each Wrong Option is Incorrect**
**Option A:** "Lichen planus is contagious."
❌ False: It is **not contagious**; it arises from immune dysregulation, not transmissible pathogens.
**Option B:** "Oral mucosa is commonly involved."
✅ True: Over 50% of cases have oral lesions, often painless and erythematous.
**Option C:** "Wickham’s striae are pathognomonic."
✅ True: These striae are diagnostic and appear as lacy, white, reticular lines on skin or mucosa.
**Option D:** "Lichen planus pigmentosus is a variant."
✅ True: This form presents with hyperpigmented patches, primarily on sun-exposed areas.

**Clinical Pearl / High-Yield Fact**
Never confuse lichen

✓ Correct Answer: C. Rarely involves mucosa