The skin disease known as psoriasis affects an estimated 10 million Americans—about 4 percent of the population. About half of these affected people have psoriasis symptoms in their nails, and 1–5 percent experience symptoms only in their nails.

Toenail (or fingernail) psoriasis—also known as psoriatic nail disease—is not merely a cosmetic condition. It can interfere with the ability of a nail to protect the toe or to perceive touch.

Toenail psoriasis can also be quite painful, and the pain can restrict movement, making it difficult for the affected person to walk normally.

This can cause an antalgic (painful) gait. In addition, a damaged psoriatic nail can make the nail plate more susceptible to fungal infections.

Psoriatic nail disease is also associated with a serious condition known as psoriatic arthritis—80 percent of people who suffer from psoriatic arthritis have had nail psoriatic nail disease.

Symptoms of Toenail Psoriasis To Watch For

Symptoms of psoriatic nail disease vary according to the severity of the condition. These symptoms may include:

• Pitting of the nail, causing the appearance of tiny craters
• Small white spots on the nail known as leukonychia
• Splinter hemorrhages: these small bleeding spots under the nail are often visible as dark lines that run parallel to the direction of the nail’s growth and resemble wooden splinters under the nail
• The “oil drop sign,” a red, orange, or brown discoloration of the nail bed, named for its resemblance to a drop of oil under the nail
• The whitish, half-moon-shaped area of the nail known as the lunula may develop red spots

When toenail psoriasis becomes more severe, the nail may begin to separate from the nail bed, a condition known as onycholysis.

Subungual hyperkeratosis, a thickening of the nail bed, may also occur. If this happens, a chalky material will begin to accumulate under the nail, further contributing to onycholysis.

The nail may eventually separate entirely from the nail bed, or it may crumble away. This condition has a very similar appearance to fungal nails. Your doctor should biopsy your nail first before any treatment to confirm if your nail is infected with fungus or if it is psoriatic nail changes.

How Did I Get Toenail Psoriasis?

It is not known exactly what causes psoriasis. The disease is known to have a strong genetic component—a third of all sufferers have a family history of psoriasis, and if an identical twin develops the disease it is 70% likely that the other twin will also develop it—but other factors also seem to have an effect.

Certain drugs and medications have been reported to cause psoriasis, and lifestyle factors such as drug and alcohol abuse, stress, smoking, and obesity are all known to exacerbate existing cases. Environmental factors such as excessive heat or dryness can also have this effect.

Complications of Toenail Psoriasis You Should Be Aware Of

As noted above, toenail psoriasis can lead to a condition known as onycholysis, in which the nail detaches from the nail bed. This can allow bacteria access to the nail bed, leading to infection.

Subungual hyperkeratosis, the accumulation of a chalky substance under the nail, can cause the nail to become raised, which may be painful and can cause difficulty walking normally or wearing shoes.

Diagnosing Toenail Psoriasis – What to Expect

Toenail psoriasis is often misdiagnosed as a fungal infection under the toenail (onychomycosis); the symptoms of these conditions are often the same and can be difficult to distinguish, particularly if your doctor does not have a background in dermatology.

Differential diagnosis of toenail psoriasis from toenail fungus is further complicated by the fact that toenail psoriasis can often cause onychomycosis.

One test that is frequently employed to distinguish fungal infections from other skin disorders is the KOH wet mount. This involves taking a specimen from under the nail and examining it under a microscope.

Potassium hydroxide is applied to the sample, which dissolves hair, skin cells, and other debris, leaving behind any fungus that may be present. If the KOH test is inconclusive, your doctor may take a sample of your nail for biopsy.

How Is Toenail Psoriasis Treated?

Unfortunately, not many good treatment options exist for toenail psoriasis. Conservative treatment usually begins with topical corticosteroid creams or ointments, or non-steroidal alternatives such as Tazorac and Dovonex.

The drawback to these creams and ointments is that they may not penetrate the nail plate adequately. Also, long-term steroid use can cause the skin and nails to thin—which takes months to grow out.

Another treatment option is phototherapy. This involves treating the nails with topical or systemic psoralen compounds, which cause the nail to respond to ultraviolet light.

According to some experts, the best treatment involves intralesional steroid injections. This means injecting cortisone into the base of the nail and into the nail folds alongside it. This treatment can be effective, and when done properly it is not as painful as it sounds.

Proper care of your feet and nails is vitally important if you have psoriasis. Avoid getting pedicures, as nail salon personnel often treat the nails roughly, and many of them trim cuticles,  , which allows bacteria to enter the nail , and is especially bad for persons affected with toenail psoriasis.

Keep your toenails short to avoid injury, and try to keep the nail folds clean and dry. Above all, one of the best treatments for psoriatic nails is control of your overall psoriasis.