Psoriasis is a common chronic condition of the skin. A person with psoriasis typically has patches of raised, red skin with silvery scales. The affected skin may look shiny and red or even have pustules, depending on the type of psoriasis the individual has. These skin changes usually occur on the elbows, knees, scalp, and trunk. In the United States, about 7 million people (2%-3% of people) have psoriasis. About 150,000-260,000 new cases are diagnosed each year. Psoriasis can also affect the fingernails and toenails, causing pitting, thickening and irregular contour of the nail. Most people who have psoriasis of the nails also have skin psoriasis (cutaneous psoriasis).
Only 5% of people with psoriasis of the nails do not have skin psoriasis.
In people who have skin psoriasis, 10%-55% have psoriasis of the nails (also called psoriatic nail disease).
Up to 25% 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, often with pitting.
If psoriasis of the nails is severe and is not treated, it can lead to functional and social problems.
Psoriasis is not contagious. How psoriasis of the nails develops is not completely known. It appears to result from a combination of genetic (inherited), immunologic, and environmental factors.
Psoriasis tends to run in families. If you have a parent or a sibling who has psoriasis, you have a 16%-25% chance of having psoriasis, too. If both of your parents have psoriasis, your risk is 75%. Males and females are equally likely to have psoriasis. Psoriasis can occur in people of all races.
Nail Psoriasis Symptoms
Usually, if psoriasis affects your nails, you have skin symptoms, too. If you have psoriasis of the nails but do not have skin symptoms, the condition may be difficult for your doctor to diagnose. Inform your doctor if you have a family history of psoriasis.
Your nail area is made up of a nail plate, nail bed, hyponychium, nail matrix, nail folds, cuticle, anchoring portion, and ends of the finger bones. You can see each of these structures in images 1-2.
If you have psoriasis of the nails, you might notice the following signs:
Clear yellow-red nail discoloring that looks like a drop of blood or oil under the nail plate: Your doctor may refer to this as an oil drop or a salmon patch. This is a sign you have nail psoriasis.
Little pits in your nails: A doctor may call this pitting of the nail matrix. Pits develop when cells are lost from the nail's surface.
Lines going across the nails (side to side rather than root to tip): These are also called Beau lines of the nail. Cells respond to psoriasis by becoming inflamed from time to time, which causes these lines.
Areas of white on your nail plate: Also called leukonychia or midmatrix disease. It is also caused by a reaction of your cells to psoriasis.
Thickening of the skin under your nail: The doctor may call this subungual hyperkeratosis. This can lead to loosening of the nail.
Loosening of the nail: Also referred to as onycholysis of the nail bed and nail hyponychium. Your nail may develop a white area where it is separated from the skin underneath your nail. It usually starts at the tip of the nail and extends toward the root. The nail bed (skin under your nail) may become infected.
Crumbling of the nail: The condition is also called nail plate crumbling at the nail bed or nail matrix. The nail weakens because the underlying structures are not healthy.
Tiny vertical black lines in the nail: Your doctor may call this a splinter hemorrhage or dilated tortuous capillaries in the dermal papillae. This occurs when the tiny capillaries in the tip of your fingers bleed between the nail and the skin under the nail.
Redness of the pale arched area at the bottom of your nail: Also called spotted lunula. It occurs when the capillaries under the nail are congested.
Arthritis of your fingers with nail changes: The nails are affected in 53%-86% of people who have psoriatic arthritis.
Nail psoriasis can also occur together with fungal infections of the nail (onychomycosis) and inflammation of the skin around the edges of your nail (paronychia).