Psoriasis can affect the nails in up to 50 percent of patients, and this number can be higher if psoriatic arthritis is present. Some people might have only nail psoriasis with no apparent skin changes on the rest of the body. Psoriasis of the fingernails is more common than psoriasis of the toenails. Several changes can occur in the nail with psoriasis.
Pitting: The most common finding in nail psoriasis is pitting. Pits are shallow depressions or dents, less than 1 mm in diameter, and look like pin holes. They can affect all nails, some or none.
Thickening or lifting of nail plate: The affected nail might thicken or lift away from the skin attached to the nail. When the nail lifts away from the nail bed it is called onycholysis. It usually begins at the edge or at the end of the nail and may continue backward under the nail until it is completely loosened from the nail bed.
Color change: The nail can develop a yellow-brown discoloration that might involve the entire nail. The discoloration can also occur in only one or a few localized areas in a spotlike manner and resemble an oil droplet.
Other changes: Other changes in nail psoriasis include depressions in the nail, roughness and grooving of the nail. If severe, patients may lose their nails, making it difficult to grasp objects! Bacterial and fungal infections may also develop in a nail already affected with psoriasis.
Fungal infections of the nails: A fungal infection of the nails (which may occur along with nail psoriasis) can also cause thickening of the nails. It is not uncommon for nail psoriasis to be misdiagnosed as a fungal infection. Fungal infections should be treated, if possible, because they can worsen psoriasis.
In order to make a proper diagnosis, a doctor takes nail clippings and a fungal culture. Once an infection is confirmed, treatment is most effective with oral antifungals. Topical treatment of nail fungus is usually ineffective, although new nail lacquers may be effective in certain patients.
Nail psoriasis is difficult to treat; both patients and dermatologists are often disappointed with the results. Treatment can take prolonged periods before improvement is seen. Topical treatments are generally ineffective in treating nail disease. Systemic treatments (oral or injectable medications) can improve nail psoriasis. Methotrexate and cyclosporine can be particularly effective, but it is important to compare the risks of therapy with the benefits of treatment. If only the nails are affected, systemic medications are rarely used because the risks of therapy usually outweigh the benefits. If extensive areas of the body are affected, systemic therapy may be a reasonable option. Also, intralesional injections of corticosteriods can be effective, but because it is painful, few patients tolerate this treatment.
If you receive an oral or injectable medication and the psoriasis elsewhere on the body shows improvement, the nail psoriasis may also improve. Scarring or permanent nail loss does not occur in nail psoriasis even in the most severe cases, but it can take 6 to 12 months for a fingernail, and 12 to 18 months for a toenail to be replaced.