Vertically growing ectopic nail.

A 64-year-old Japanese woman with an ectopic nail at the palmar tip of the left middle finger is reported. Interestingly, the nail grew vertically to a line horizontal to the surface epidermis. Atypically, it appeared at 60 years of age with no prior injury or trauma to explain inoculation of a nail matrix into the regional skin. Roentgenographically, there were no abnormal findings such as Y-shaped bifurcation of the distal phalanx of the affected finger. There are conflicting opinions concerning whether or not a proximal nail fold is critical for the nail to grow outward instead of upward. Although the present case had a wide proximal nail fold, it did not seem to play its role of compressing and assisting the nail plate to grow outward. Hence, it may be that the absence of a proper nail bed, rather than the absence of a proximal nail fold, promotes upward growth of a nail plate instead of outward growth.