ABSTRACT
Nails are keratin produced by a modified epidermis called the nail matrix. Nails protect the end of the digits and on the fingers are useful for picking up small objects and for scratching. Abnormalities can arise from any part of the nail apparatus. The nail bed is the epidermis underneath the nail. Problems in the nail bed cause areas of discolouration under the nail. Onycholysis is separation of the nail plate from the nail bed. It is due to an abnormality of the hyponychium where the nail plate is less firmly stuck down onto the nail bed. Involvement of the hyponychium at the distal end of the nail will result in onycholysis and if there is a build-up of scale underneath, subungual hyperkeratosis. Lichen planus affects the nail matrix and the cuticle. Longitudinal ridging and splitting of the nail plate can occur.
