## **Core Concept**
The dorsal pterygium of the nail is a condition characterized by the scarring of the nail bed and the fusion of the nail plate to the overlying tissues, often resulting from trauma or certain diseases. This condition leads to the obliteration of the nail plate and is associated with various systemic and local conditions.

## **Why the Correct Answer is Right**
Option correctly identifies that dorsal pterygium of the nail is seen in **Lichen planus**. Lichen planus is a chronic inflammatory condition that affects mucous membranes inside the mouth and also the skin. When it affects the nails, it can cause scarring and lead to the formation of dorsal pterygium. This occurs due to the inflammation and scarring process associated with lichen planus, which can cause the nail plate to become adherent to the overlying tissue.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a condition known to cause dorsal pterygium.
- **Option B:** This option is incorrect as it does not accurately represent a condition associated with dorsal pterygium of the nail.
- **Option D:** This option is incorrect because it does not correctly identify a condition known to cause dorsal pterygium.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that lichen planus can affect the nails and lead to scarring, manifesting as dorsal pterygium. This condition can result in permanent damage to the nail apparatus. Recognizing lichen planus as a cause of nail scarring is crucial for diagnosis and management.

## **Correct Answer:** . Lichen planus