Pterygium of nail is seen in –
## **Core Concept**
Pterygium of the nail refers to a condition characterized by the formation of a wing-like or feather-like scar tissue that adheres to the nail plate and underlying tissues, often leading to distortion or destruction of the nail. This condition can result from trauma, inflammation, or certain diseases affecting the nail apparatus.
## **Why the Correct Answer is Right**
The correct answer, **C. Lichen planus**, is associated with pterygium of the nail because lichen planus is a chronic inflammatory condition that can affect the skin, mucous membranes, and other areas, including the nails. In the context of nail involvement, lichen planus can cause scarring and lead to the formation of pterygium, particularly a condition known as pterygium unguis, where there is scarring and adhesion within the nail apparatus.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Psoriasis is a chronic autoimmune skin condition that can affect the nails, causing changes such as pitting, onycholysis (separation of the nail from the nail bed), and subungual hyperkeratosis. However, it is less commonly associated directly with the formation of pterygium compared to lichen planus.
- **Option B:** Pemphigus vulgaris is an autoimmune disease that causes blistering of the skin and mucous membranes. While it can affect the nails indirectly through blistering or secondary infection, it is not typically associated with pterygium formation.
- **Option D:** Alopecia areata is an autoimmune condition that primarily affects hair follicles, leading to hair loss. It can also affect the nails, causing changes such as nail pitting, but it is not commonly associated with pterygium.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that lichen planus can cause scarring in the nails, leading to pterygium formation, which is a distinguishing feature from other conditions like psoriasis or alopecia areata that affect the nails but typically do not cause scarring leading to pterygium.
## **Correct Answer: C. Lichen planus**