ABSTRACT
This chapter discusses the histopathology and differential diagnosis of some of nail specific conditions, such as anonychia and hyponychia, leukonychia, erythronychia, Green nails, Brown and Black nails, subungual hematoma, onycholysis, subungual hyperkeratosis, onychogryposis, pterygium inversum, pterygium, overcurvature, Beau's Lines and onychomadesis. Examination of biopsies from a lichen planus-induced nail degloving exhibited a naked dermis with a superficial band of lymphocytic infiltrate in the proximal nailfold and the matrix thus closely resembling the dermal portion of lichen planus. The depression of the nail in pits is easily seen in a nail clipping. Trachyonychia is a sign of various nail conditions, both congenital as well as acquired inflammatory. Pseudo-mycotic onychia requires exclusion of a fungal infection, of the asymmetric gait nail unit syndrome, and of long-standing alopecia areata. Retronychia describes retrograde ingrowing of the nail. Ingrown nails are observed in all ages from newborns to the old.
