ABSTRACT
Hard nails are not uncommon on the toes, where they may present as onychogryphosis. In contrast, hard finger nails are unusual and are principally observed in an ectodermal dysplasia, pachyonychia congenita. The nails become yellowish-brown usually within months after birth and show subungual hyperkeratosis with elevation of the nail plate. The nails become progressively thicker and wedge-shaped. Jadassohn had to use a hammer and chisel on the hardened nails of his patient.
