ABSTRACT
There are various causes of grooves, ridges, and pits, including local trauma to the nail matrix, and acute febrile systemic disease. Poor nutrition to the matrix leads to a defective band of nail formation resulting in a transverse groove on the thin nail plate (Beau’s line) (Figure 4.1). Recurrent disease will produce recurrent transverse grooves separated by the normal nail. The depression may extend all the way to the nail plate, leading to temporary latent onychomadesis (Figure 4.2), followed by loss of nail. By measuring the position of the transverse grooves, it is possible to date the previous illness. Transverse grooves sometimes found in psoriasis may be present in isolation or multiple. These should be differentiated from washboard nails (Figure 4.3), in which there is also a longitudinal depression usually affecting one or both thumb nails and resulting from a habit-tic pushing back of the cuticle.
