Okay, let's tackle this question about aphthous ulcers. The question is asking which statement is NOT true about them. First, I need to remember the core concepts of aphthous ulcers. They're those painful mouth ulcers, right? Also known as canker sores. They're not contagious and can be caused by stress, trauma, or nutritional deficiencies. The types include minor, major, and herpetiform. Now, the options aren't provided, but the correct answer is supposed to be the exception.

So, common facts about aphthous ulcers: they're not caused by HSV (herpes simplex), which causes cold sores. HSV leads to grouped, painful vesicles, not ulcers. Also, aphthous ulcers can be associated with conditions like Crohn's disease or celiac disease. They usually heal on their own in 7-14 days. Treatment is mainly symptomatic with topical anesthetics or corticosteroids.

The incorrect options might include HSV as a cause, which is wrong. Another incorrect point could be that they are contagious, but they aren't. Also, if an option says they are caused by bacterial infection, that's incorrect. The correct answer here would be the one that states HSV as the cause. Let me structure the explanation accordingly. Need to make sure each wrong option is addressed clearly. The clinical pearl should highlight the non-contagious nature and differentiation from HSV. Alright, putting it all together in the required sections.

**Core Concept** Aphthous ulcers are non-contagious mucosal lesions caused by immune-mediated mechanisms, not viral infections. They differ from herpetic ulcers (HSV) in presentation, etiology, and treatment.

**Why the Correct Answer is Right** The false statement is that aphthous ulcers are caused by herpes simplex virus (HSV). HSV causes grouped vesicles that ulcerate, while aphthous ulcers are solitary or clustered, shallow ulcers with a red halo. HSV lesions are contagious and occur on keratinized mucosa, unlike aphthous ulcers. Diagnosis relies on clinical history and exclusion of systemic diseases (e.g., Behçet’s disease).

**Why Each Wrong Option is Incorrect**
**Option A:** "Associated with stress" – True; stress is a common precipitant.
**Option B:** "Self-limiting in 7–14 days" – True; minor aphthous ulcers resolve spontaneously.
**Option C:** "Treated with topical corticosteroids" – True; reduces inflammation and pain.
**Option D:** "Occur on keratinized mucosa" – False (if this were the correct answer); aphthous ulcers typically occur on non-keratinized mucosa (e.g., buccal lining, tongue).

**Clinical Pearl / High-Yield Fact** Aphthous ulcers are *not* caused by HSV. HSV lesions are grouped, vesicular, and contagious. Remember: "HSV = clusters, aphthous = singles." Use this to differentiate in exams and clinics.

**Correct Answer: D. Occur on keratinized mucosa**

✓ Correct Answer: B. Deep ulcers