**Question:** Wickham's striae are seen in:

A. Diabetes
B. Viral infections
C. Drug reactions
D. Systemic lupus erythematosus

**Core Concept:**

Wickham's striae, also known as Cowden's striae or oral erosive lichen planus, are characteristic mucocutaneous findings observed in certain clinical conditions. They are caused by the activation of keratinocytes, leading to the formation of keratinocyte necrosis, which results in the histopathological feature of Wickham's striae. The striae typically appear as white or pale, reticular, and interlaced streaks in the oral mucosa, appearing as a "spider web" or "sausage skin" appearance.

**Why the Correct Answer is Right:**

C. Drug reactions (specifically, allergic reactions) are the most common cause of Wickham's striae. These reactions lead to an immune response, causing inflammation, and subsequently, keratinocyte necrosis, which results in the formation of Wickham's striae.

**Why Each Wrong Option is Incorrect:**

A. Diabetes is a risk factor for oral lichen planus, but it is not the primary cause of Wickham's striae. Oral lichen planus is a separate entity characterized by white papules and plaques, rather than striae.

B. Viral infections like herpes simplex virus (HSV) can lead to oral lesions, but the typical appearance of Wickham's striae is not associated with viral infections.

D. Systemic lupus erythematosus is a systemic autoimmune disorder affecting multiple organs, not specifically related to oral lesions. Unlike Wickham's striae, systemic lupus erythematosus is characterized by mucocutaneous lesions such as mucosal ulcers, malar rash, and photosensitivity.

**Clinical Pearl:**

Drug reactions, particularly allergic reactions, are essential to consider when assessing patients with oral lesions. Careful clinical examination and history-taking can help differentiate Wickham's striae from other oral lesions and guide appropriate management.