Pterygium of the nail can occur at which of the following locations?

Pterygium of the nail is specifically linked to issues with the eponychium, which is the tissue that overlaps the base of the nail. When pterygium occurs, it generally refers to the abnormal growth or a thickening of the skin that can extend from the eponychium onto the nail plate. This condition is often a result of trauma, infection, or other nail disorders.

Understanding the anatomy of the nail is essential in this context; the eponychium serves as a barrier and protective layer for the underlying nail structure. Damage or conditions affecting this area can lead to the development of pterygium. In contrast, the other locations—nail matrix, nail tip, and nail bed—are less commonly associated with the development of pterygium. The nail matrix is where the nail grows, the nail tip is the free edge of the nail, and the nail bed is the skin beneath the nail plate, none of which typically present with the characteristics of pterygium.