woman looking at her feet

Nail Psoriasis and Fungus: How to Tell the Difference

By Kerry Weiss
Reviewed by Allison Truong, M.D.
May 06, 2024

Psoriasis is known as a skin disease, but it can sometimes affect fingernails and toenails, as well. According to the National Psoriasis Foundation, approximately 90 percent of people with psoriasis will experience nail psoriasis at one point or another.

Nail fungus is also quite common, thought to affect as much as 12 percent of the population. As both cause discoloring and thickening of the nails, how do you know if you’re dealing with nail psoriasis or just your run-of-the-mill nail fungus?

“To patients, psoriasis and nail fungus can look similar,” says Neil Korman, M.D., Ph.D., clinical director of the Murdough Family Center for Psoriasis at University Hospitals in Cleveland, Ohio. But they’re actually quite different. Nail psoriasis is caused by having psoriatic disease, which, while it never really goes away, may be eased with treatment. Nail fungus is an infection of the nail caused by fungi in our environment and that needs specific antifungal treatment.

Because these conditions can resemble each other but are actually caused by different things, it’s important to see a dermatologist to get a correct diagnosis and to find the right treatment. Here’s what else is important to know to understand the difference between nail psoriasis and fungus.

Symptoms of Nail Fungus and Nail Psoriasis

While nail psoriasis and fungus might seem similar at first glance, “There’s a difference in clinical appearance,” says Wang.

Nail fungus is more likely to occur on your toenail, where the nail may appear:

  • Discolored yellow, brown, or white
  • Thickened
  • Cracked, crumbly, or fragile
  • Flaked with dead skin (keratin) under the nail

Typically, nail fungus isn’t painful, unless it’s left untreated and becomes more severe.

“Many people who experience nail fungus have a prior history of athlete’s foot,” says Frank Wang, M.D., a professor of clinical dermatology and the assistant program director of the Dermatology Residency Program at Michigan Medicine in Ann Arbor. Athlete’s foot, also known as tinea pedis, presents with dry skin or scaling on the bottom of the feet and on the skin between the toes.

Meanwhile, nail psoriasis is more likely to occur on the fingernails, often affecting multiple nails at once. It may appear as:

  • Pitting on the nail’s surface, which looks like little holes on the top of the nails
  • Lifting of the nail from the nail bed, also known as onycholysis
  • Deformity in nail shape; nails can appear smaller when the nail is separated from the pink portion of the nail called the nail bed
  • Discoloration of brown or yellow, or the development of salmon-colored spots under the nail; this appears as little oil droplets on the nail
  • Thickening or thinning of the nail

Pain is more often associated with nail psoriasis, and it can hurt so badly that it can affect your day-to-day activities.

“Nail psoriasis can also be a marker of or coexist with psoriatic arthritis,” adds Korman, as 80 percent of people with psoriatic arthritis also have nail psoriasis. “That’s why it’s really critical to see a doctor with expertise in psoriasis.” Psoriatic arthritis tends to be degenerative, meaning it gets worse over time, potentially eventually causing disfigurement called psoriatic arthritis mutilans. This end-stage form of psoriatic arthritis may lead to significant disability, as it limits range of movement and causes chronic pain.

Diagnosing Nail Fungus and Nail Psoriasis

To diagnose the root cause of your symptoms, your doctor will assess your nails and ask questions about what you’re experiencing. They may also clip a piece of your nail to review under a microscope, or have the sample sent to a laboratory to perform a culture, which checks for fungus.

“For someone with psoriasis who has nail disease and we don’t know what it is, the culture is a very critical part of determining the diagnosis,” says Korman, who emphasizes that the nail sample should be sent to a lab that specializes in knowing how to read these nail cultures.

“A negative culture for someone with psoriasis tells us that they probably don’t have any nail fungus, just psoriasis of the nails,” he adds.

And identifying or ruling out nail fungus as opposed to psoriasis is an important factor in determining the proper course of treatment.

How to Treat Nail Fungus vs. Nail Psoriasis

Treatment options for nail fungus differ from those that treat nail psoriasis. Nail fungus likely won’t go away on its own. It has to be treated with an antifungal; even then, it can take months to clear the infection.

While both topical and oral antifungal options exist, the orals are considered to be the first-line therapy for nail fungus. “Topicals can help it look and feel a little better, but rarely make it go away,” says Korman. “The only thing that really makes it disappear is oral medication.” Topicals include over-the-counter options such as Vicks VapoRub and tea tree oil or prescription options such as ciclopirox (Penlac), efinaconazole (Jublia), and tavaborole (Kerydin). Oral prescription options include terbinafine (Lamisil) and itraconazole (Sporanox).

What’s more, adds Korman, is that many people with known psoriasis may develop nail fungus that’s properly diagnosed and treated, yet they still have nail symptoms, which means it’s likely nail psoriasis, as well.

“Being that nail fungus and nail psoriasis are both conditions that are quite common, you’ll definitely encounter patients who may have both,” adds Wang.

When it comes to treating nail psoriasis, the exact location where the nail is affected helps determine the proper course of treatment. Options include topicals (such as clobetasol), steroid injections into the skin around the nail called the proximal nail fold to target the nail matrix (where the nail cells are made), phototherapy, laser therapy, oral medications, and biologics.

Not all treatment options are equal when it comes to treating nail psoriasis, says Korman. “What works best for nail psoriasis is what works well for people who have really bad psoriasis, in general, which are the biologic agents.”

Your doctor may even prescribe a combination of medications to clear your nail psoriasis, and it can take time to find the right treatment or combination of treatments for you. Then, once you do, it can take months of following your treatment plan as directed to achieve maximum results. The issue is that fingernails usually take about six months to grow out and toenails take about 12 months to grow out, so it takes time for treatment to show beneficial results.

When to Seek Treatment

When it comes to treatment, one of the most important factors to discuss with your doctor is how much your symptoms are affecting you.

“Neither nail fungus nor nail psoriasis is dangerous,” explains Wang.

“It only becomes worrisome if it’s bothering the patient,” adds Korman. Both these conditions can affect your appearance—which may take a toll on self-esteem and quality of life. They may also affect your ability to use your hands and feet, or to carry out your day-to-day activities.

So when should you seek out treatment? “When it bothers you enough that you’re unhappy,” says Korman. “Or if you’re also experiencing symptoms like pain, swelling, or stiffness in the joints, which could be signs of psoriatic arthritis. These are indicators of when you should consider seeing a psoriasis expert.”

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