What is Psoriasis of the Nails?

About 50 percent of people with active psoriasis have psoriatic changes in fingernails and/or toenails. In some instances psoriasis may occur only in the nails and nowhere else on the body. Psoriatic changes in nails range from mild to severe, generally reflecting the extent of psoriatic involvement of the nail plate, nail matrix (tissue from which the nail grows), nail bed (tissue under the nail), and skin at the base of the nail. Damage to the nail bed by the pustular psoriasis can result in loss of the nail.

Nail changes in psoriasis fall into general categories that may occur singly or all together:
The nail plate is deeply pitted, probably due to defects in nail growth caused by psoriasis.
The nail has a yellow to yellow-pink discoloration, probably due to psoriatic involvement of the nail bed.
White areas appear under the nail plate.
These are air bubbles marking spots where the nail plate is becoming detached from the nail bed (onycholysis).
There may be reddened skin around the nail.

The nail plate crumbles in yellowish patches (onychodystrophy), probably due to psoriatic involvement in the nail matrix.The nail is entirely lost due to psoriatic involvement of the nail matrix and nail bed.