ABSTRACT
Congenital and hereditary nail dystrophies are classied according to the defects occurring in the nail matrix, the nail eld, or the nail bed.1
The nail eld is the area where the nail matrix and the nail bed develop. A defect in the matrix is the most common cause of abnormal nails. The matrix can have an abnormal position, size, or quality. Proliferation of the nail bed will produce a thickened nail which, as in pachyonychia congenita, is not evident until early childhood (Table 3.1).
