The nail apparatus: A guide for basic and clinical science

The nail apparatus has a limited number of ways it can express pathology. A basic understanding of the normal anatomy and physiology of this complex s kin appendage is necessary to determine the site of pathology, formulate a differential diagnosis, and determine the appropriate workup. A more in-dep th understanding of anatomy is absolutely crucial when performing diagnosti c and therapeutic surgical procedures. Our understanding of nail unit biolo gy is small in comparison with skin and hair biology, probably because of t he difficult access to this organ. However, during the past decade, there h ave been many important advancements in our knowledge that are vital to an improved understanding of inflammatory, infectious, and neoplastic disease of the nail apparatus. This article is an update of nail anatomy and biolog y, as well as an update of many types of common nail disease. It is intende d to serve as a practical guide for the dermatologist caring for patients w ith nail disorders.