When Psoriatic Disease Strikes the Hands and Feet

Location Matters

To get an idea of the impact of psoriatic disease on the hands and feet, think of the pain of a hangnail on a finger or a blister on a foot, and how much these small injuries consume your attention and interfere with daily tasks, says Kristina Callis Duffin, M.D., co-chair of the department of dermatology at the University of Utah in Salt Lake City.

“Having psoriasis or psoriatic arthritis on the hands and feet is life-altering,” she says. “It raises the bar for how much it affects your quality of life.”

Duffin was the lead investigator for a study comparing people who have psoriasis on the palms of the hands and soles of the feet (called palmoplantar psoriasis) with those who have the disease elsewhere. The study, published in the September 2018 Journal of the American Academy of Dermatology, found that those with hand and foot involvement were almost twice as likely to report problems with mobility and almost two-and-a-half times more likely to say they had trouble completing usual activities.

“Those with palmoplantar psoriasis scored much worse on multiple quality-of-life measures, even though they typically had less total affected body surface area,” says Duffin, who is also an NPF medical board member.

Body surface area is one way dermatologists measure psoriasis severity and decide how aggressively to treat it. But it’s not the best tool for making treatment decisions when the hands or feet are affected, Duffin says. “In those cases, we often start treatment with a biologic even when the total involved body surface area is relatively small.”

PsA also hits especially hard when it affects hands and feet.

“If joints in the hands and feet are hurting and swollen, it can affect every aspect of their function,” says Alice Gottlieb, M.D., Ph.D., clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York City and an NPF medical board member.

Types, Symptoms and Treatment

Like psoriasis and PsA elsewhere on the body, psoriatic disease in the hands and feet can cause itchy, scaling, reddened skin plaques and painful, swollen joints. Specific types and symptoms of hand and foot psoriasis and PsA, however, can also cause less-familiar skin and joint issues.

Palmoplantar psoriasis, plaque psoriasis on the feet or hands, affects about 40 percent of people with plaque psoriasis, who often don’t have much skin disease elsewhere. As noted, its substantial effects on function and quality of life mean dermatologists typically use advanced medications to control symptoms. Treating certain types of palmoplantar psoriasis is still challenging, despite the rapidly expanding list of medications for psoriasis and PsA. Often, palmoplantar psoriasis doesn’t respond as well to treatment as does psoriasis on other parts of the body.

Most biologics, which work by targeting specific proteins that turn up inflammation in psoriatic disease, such as tumor necrosis factor (TNF) or interleukin-17 (IL-17), have some effect on certain people with palmoplantar psoriasis.

No one treatment works for everyone, and people with palmoplantar psoriasis may have to try several medications or combinations of treatments to relieve symptoms. Gary Bixby, for example, didn’t get better with either a TNF or an IL-17 inhibitor. The third biologic he tried blocks another interleukin protein, IL-23, and, three months after his first injection, he’s getting better results.

“I’m seeing improvements in my fingernails and the plaques on my body, which I didn’t get with the first two biologics. I’m cautiously hopeful,” he says.

Palmoplantar pustular disease, or pustulosis, affects about 5 percent of people with psoriasis. It shows up as small, pus-filled blisters on reddened, tender skin. It can also cause painful cracking
and fissuring.

Biologics can sometimes make pustular disease worse, says Duffin, so dermatologists may decide to begin treatment with a traditional disease-modifying antirheumatic drug (DMARD) such as methotrexate or cyclosporine.

“There are also new medications in development, specifically anti-IL-36 biologics, that could be a good treatment pathway for pustular psoriasis,” says Duffin.

Psoriatic nail disease can cause a host of symptoms in both the nail bed and the matrix, the area where fingernails and toenails start their growth. These include pitting, crumbling, thickening, discoloration, white or reddish spots, and separation of the nail from the nail bed (called onycholysis). None of these symptoms is specific to nail psoriasis, however, and some people have both nail psoriasis and nail fungus.

All this can make nail disease difficult to diagnose, says Duffin.

“If you have pitting, for example, you could have vitiligo or eczema instead of psoriasis,” she explains. (Vitiligo is a disease that causes skin, or sometimes hair, to lose its natural color.) “Sometimes, psoriasis patients are concerned about normal nail features, such as ridging or brittleness, that aren’t psoriasis.”

When the cause of nail symptoms isn’t clear, dermatologists look for signs of psoriasis elsewhere on the body. They may also look at a nail clipping under a microscope to distinguish one condition from another.

Once dermatologists understand what’s going on in the nails, they can decide how best to treat them. “All biologics have some data showing they can work better for nails than traditional DMARDs, but there is still no one slam-dunk treatment,” says Duffin, who notes that it can take months to learn whether a treatment is improving nail symptoms.

“It takes three to six months for nail to regrow entirely, so patients need to be on a treatment continuously for that time for us to know whether it’s working,” she says.

Nail psoriasis is also a risk factor for PsA, and when it occurs with other symptoms, may prompt a referral to a rheumatologist, who can evaluate you for joint disease.

Dactylitis, sometimes called “sausage” fingers or toes, is the painful swelling of digits that can occur with PsA. “When people have dactylitis, all the structure of the digits are inflamed, and this means every aspect of their function is impaired,” says Gottlieb.

Enthesitis, the swelling of the entheses, the connective tissue that joins ligaments and tendons to bone, can cause discomfort in the hands and feet of people with PsA. The sole of the foot and the back of the heel, where the Achilles tendon inserts into the heel bone, are common sites for enthesitis.

Treating PsA with appropriate medications, typically a DMARD or a biologic, should also relieve symptoms of dactylitis and enthesitis, Gottlieb says.

Researchers are now focusing more on hand and foot symptoms in clinical trials. That means physicians are getting better data about what works for specific symptoms, says Gottlieb, who is triple board-certified in dermatology, rheumatology and internal medicine.

TLC for Hands and Feet

Avoiding injuries, even small ones (often called microtraumas), makes good sense for people with psoriasis or PsA affecting the hands and feet.

“The Koebner phenomenon is the flaring of psoriasis in response to injury. Even minor trauma can cause a flare,” says Duffin. “For example, if you use your nails to pry open a lid, you’re probably going to make your nail psoriasis worse.”

Similarly, shoving feet into shoes without enough room to wiggle toes or wearing high heels means you’re putting constant pressure on nails and joints, which can increase pain and nail problems.

“I generally recommend flats that have good cushioning and arch support that takes the weight off toe joints – which doesn’t mean wearing ballet slippers that have no padding in the bottom,” says Gottlieb.

“You don’t want a triangle profile that squeezes the toes, because that elicits pain.” She also cautions that flip-flops, a summer favorite, expose toes and feet to trauma.

A consultation with a podiatrist, who can advise on the right footwear and design an orthotic for individual foot issues, is often helpful for people with PsA that affects the feet, Gottlieb says.

Photo: Aaron Coury