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Types of Psoriasis (cont.)

Nail Psoriasis

Nail psoriasis can affect the fingernails and toenails.

Nail psoriasis of the fingernails and toenails. Note discoloration. Image courtesy of Hon Pak, MD.

Most people who have psoriasis of the nails also have skin psoriasis (also called cutaneous psoriasis or just psoriasis). Psoriasis of the nails occurs in fewer than 5% of people who do not have skin psoriasis. In people who have skin psoriasis, 10-55% have psoriasis of the nails (also called psoriatic nail disease). About 10-20% of people who have skin psoriasis also have psoriatic arthritis, a specific condition in which people have symptoms of both arthritis and psoriasis. Of people with psoriatic arthritis, 53-86% have affected nails.

Psoriasis of the nails involves any of a number of changes to the nail area. Clear yellow-red nail discoloring that looks like a drop of blood under the nail plate may occur. Little pits may form in the nails. These pits develop when cells are lost from the nail's surface.

Nail psoriasis with pitting. Image courtesy of Hon Pak, MD.

Lines may develop going across the nails (side to side rather than root to tip). Areas of white on the nail plate may also be present.

The skin under the nail may thicken and lead to loosening of the nail. A white area may develop on the nail where it is separated from the skin underneath. This usually starts at the tip of the nail and extends toward the root. The nail bed (skin under the nail) may become infected. The nail may weaken and start to crumble because the underlying structures are not healthy. Tiny black lines may form in the nail in tip to cuticle direction. This occurs when the tiny capillaries in the tip of the fingers bleed between the nail and the skin under the nail. The pale arched area at the bottom of the nail may become red. This occurs when the capillaries under the nail are congested.

Nail psoriasis can also occur with fungal infections of the nail (onychomycosis) and inflammation of the skin around the edges of your nail (paronychia).

Psoriasis of the nails is not contagious. How psoriasis of the nails develops is not completely known. It may have a combination of genetic (family), environmental, and immune causes. If psoriasis of the nails is severe and is not treated, it can lead to functional and social problems.