Doctor's Notes on Nail Psoriasis
Psoriasis is a common, chronic skin condition that usually manifests as patches of raised, red skin with silvery scales. These skin changes in psoriasis usually occur on the elbows, scalp, knees, and trunk. Psoriasis can also affect the fingernails and toenails. The cause of psoriasis is not well understood, although it is known to run in families. Nail psoriasis most likely is caused by a combination of genetic (inherited), immunologic, and environmental factors.
Signs and symptoms of nail psoriasis include thickened nails, pitting, ridges in the nails, nails loosening from the nail bed, and irregular contour of the nails. Other associated symptoms can include crumbling of the nails, white areas on the nail plate, furrows known as Beau's lines that run across the nails, and thickened skin beneath the nail bed.
Nail Psoriasis Symptoms
Usually, people who have nail psoriasis also have skin symptoms, too. If someone has psoriasis of the nails but does not have skin symptoms, the condition may be difficult for a doctor to diagnose, since the signs of psoriasis of the nails resemble those of fungal infection of the nails. It is important to inform the doctor if there is a family history of psoriasis.
The nail unit is made up of a nail plate, nail bed, hyponychium, nail matrix, nail folds, cuticle, anchoring portion, and ends of the finger bones. See each of these structures in images 1-2.
Someone might notice the following signs with psoriatic nails:
- Clear yellow-red nail discoloring that looks like a drop of blood or oil under the nail plate: This is known as an oil drop or a salmon patch and is a sign of nail psoriasis.
- Little pits in the nails or pitting of the nail matrix. Pits develop when cells are lost from the nail's surface.
- Lines or furrows going across the nails (side to side rather than root to tip): These are medically known as Beau's lines of the nail.
- Areas of white on the nail plate, otherwise known as leukonychia or midmatrix disease
- Thickening of the skin under the nail: The doctor may call this subungual hyperkeratosis. This can lead to loosening of the thickened nail.
- Loosening of the nail (nail lifting): This is medically referred to as onycholysis of the nail bed and nail hyponychium. The nail may develop a white area where it is separated from the skin underneath the nail. Onycholysis usually starts at the tip of the nail and extends toward the root. The nail bed (skin under the nail) may become infected.
- Crumbling of the nail: The crumbling nail can be brittle and weaken because the underlying structures are not healthy.
- Tiny black lines in the nail in tip-to-cuticle direction: These are called splinter hemorrhages or dilated tortuous capillaries in the dermal papillae. This occurs when the tiny capillaries in the tip of the fingers bleed between the nail and the skin under the nail.
- Redness of the pale arched area at the bottom of the nail: This is known as a spotted lunula. It occurs when the capillaries under the nail are congested.
- Arthritis of the fingers with nail changes: The nails are affected in 53%-86% of people who have psoriatic arthritis.
Nail Psoriasis Causes
Psoriasis is not contagious. How psoriasis of the nails develops is not completely known. Nail involvement appears to result from a combination of genetic (inherited), immunologic, and environmental factors.
Psoriasis tends to run in families. About 40% of people with psoriasis have a first-degree relative who is known to have the condition. If both parents have psoriasis, a person's risk is up to 75%. Males and females are equally likely to have psoriasis. Psoriasis can occur in people of all races.
Whether you're washing your hands or admiring a manicure, you spend a lot more time looking at your fingernails than your toenails. Maybe it's time to focus on your feet more often (and not just during sandal season). Toenail color changes -- from a big blue spot to a thin brown line -- could signal health problems. Here's what you need to know.
Psoriasis : Test Your Medical IQ QuizQuestion
Psoriasis causes the top layer of skin cells to become inflamed and grow too quickly and flake off.See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.