Some people say that the eyes are the window to the soul. Now research suggests that the fingernails may be the window to the joints—at least in people with psoriatic arthritis.
According to a study published in March 2015 in the Journal of Cutaneous Medicine and Surgery, particular kinds of fingernail psoriasis may correspond with a particular symptoms of psoriatic arthritis.
Researchers already know that fingernail psoriasis can be an early sign of psoriatic arthritis. Previous studies have found that at least 80 percent of people with psoriatic arthritis also have fingernail psoriasis, which can cause many different nail changes, including crumbling nails, ridges on the nails or discoloration.
This study, conducted by researchers in Ontario, Canada, examined 188 people with psoriatic arthritis to see if specific nail changes were tied to specific joint symptoms. Almost everyone in the study—172 patients—had some kind of fingernail psoriasis on at least one nail, according to the findings.
Patients with blood spots under the nail, also known as splinter hemorrhages, tended to have higher numbers of swollen joints, while patients with other kinds of nail psoriasis—including vertical ridges on the nail; red spots in the white, crescent-shaped area at the root of the nail; and crumbling nails—had higher numbers of tender joints, researchers reported.
The kind of nail changes occurring on a certain finger also told researchers what was happening inside the joints of that finger. Researchers found that patients with nail crumbling; separation of the nail from the skin under the nail; and a build-up of keratin under the nail, were more likely to have a swollen or tender distal interphalangeal (DIP) joint on the same finger. DIP joints are the finger joint closest to the nail.
Many kinds of fingernail psoriasis can be traced to the same inflammatory processes involved in psoriatic disease, as noted in the study.
For example, according to the researchers, inflammation where the underside of the nail meets the fingertip can lead to separation of the nail from the skin. In addition, inflammation in the nail matrix—the tissue under the nail near the cuticle—can cause nails to crumble, while psoriasis plaques on the nail matrix can lead to vertical ridges on the nail, the researchers noted.
Patients with psoriatic arthritis should have their nails examined for changes, the researchers concluded.
Nail changes seen in fingernail psoriasis
- Crumbling nails
- Onycholysis: Separation of the nail from the nail bed
- Onychorrhexis: Ridges and splitting in the nail
- Splinter hemorrhages: Spots of blood under the nail
- Subungual hyperkeratosis: Build-up of keratin between the nail and nail bed
Parts of the nail involved in fingernail psoriasis
- Hyponychium: Tissue where the underside of the nail meets the fingertip
- Lunula: Visible part of the nail matrix that looks like a crescent moon
- Nail bed: Skin under the nail plate
- Nail matrix: Tissue underneath the base of the nail
- Nail plate: Visible part of the nail
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