How Psoriasis Can Lead to Psoriatic Arthritis

About 5.5 million Americans have psoriasis, a chronic skin disease. Patients with psoriasis often have skin lesions covered with scales made up of dead skin cells that accumulate when new skin cells are made more quickly than the old ones are shed.

“Psoriasis is an autoimmune disease that occurs when the body’s immune system is overactive in the skin, as though there were a foreign invader,” said Steven R. Feldman, M.D., Ph.D., Department of Dermatology at Wake Forest Baptist Medical Center in Winston-Salem, N.C. “The first reason people see their physicians is these scaly red patches.”

Signs, Symptoms and Risks

Psoriasis signs and symptoms vary widely from one person to the next. Most include one or more of the following:

– patches of red skin and silvery scales;

– small scaling spots, most often seen in children;

– dandruff if there is involvement in the scalp;

– dry, cracked skin;itching, burning or soreness;

– thickened, pitted or ridged toenails or fingernails; and/or

– swelling and stiffening of joints seen in psoriatic arthritis.

“Different types of psoriasis are named after their different presentations,” said Feldman. “Plaque psoriasis is the most common, causing dry, raised and red skin lesions called plaques that are covered with silver colored scales. They itch, can be painful and can show up anywhere on your body. Less common is pustular psoriasis, in which small blisters of pus are visible in the lesions.”

Why psoriasis occurs is not completely understood, but some well-established risk factors exist. Most common is a genetic predisposition, or a family history of the disease. Other factors include obesity, alcohol consumption and use of certain medications such as lithium or beta-blockers. Cases are equally divided between men and women.

“The main diagnostic test for psoriasis is looking at the lesions,” said Feldman. “Usually we know it when we see it. For some atypical presentations, we may take a biopsy to confirm the diagnosis.”

Psoriatic Arthritis

One symptom of psoriasis that should be taken very seriously is joint or back pain. Even those with mild cases of psoriasis should make sure their dermatologist is told immediately when back pain occurs.

“Psoriatic arthritis is an inflammatory form of arthritis that is very different from the aches and pains of mechanical arthritis,” said Dee Dee Wu, M.D., a rheumatologist at the Hospital for Special Surgery in New York City. “Around 20-30% of those with skin disease will go on to develop inflammatory arthritis. However there is also a small subset who develop inflammatory arthritis prior to the onset of skin disease, which can make the diagnosis much harder.”

Both skin and joint psoriasis share most of the same group of risk factors, including family history. Having psoriasis of the skin increases the likelihood you will progress to psoriatic arthritis.

Medication for Psoriasis

The first intervention for psoriasis is educating the patient about the disease and its treatment options. Because the lesions are easily seen, it is important to know that psoriasis is not contagious. Learning to cope with social situations in which people may stare, point fingers or shrink away also is crucial.

“We suggest going to the National Psoriasis Foundation website,” said Feldman. “The website not only helps with learning about psoriasis, but also can help link patients with people who have personal experience in dealing with social and other issues.”

Several treatments are available for psoriasis, many of which successfully lower the extent of the disease or even get rid of it completely. The decision of which medication to try, and in what order, depends on many variables—the type of psoriasis, how extensive it is, comorbid medical conditions and the presence of other forms of inflammatory arthritis, as well as your insurance coverage and what you can afford.

Biologic Drugs: Biologic drugs (biologics) are protein-based and made from living cells in a laboratory. They are given by injection for those with moderate to severe psoriasis who haven’t responded to other treatments. There are various classes of these drugs depending on what part of the immune system they focus.

Tumor necrosis factor-alpha (TNF-alpha) blockers inhibit a signal that tells the body to create inflammation. Extra production in the skin or joints leads to growth of skin cells and/or joint damage. Drugs in this class include Cimzia (certolizumab pegol), Enbrel (etanercept), Humira (adalimumab), Remicade (infliximab) and Simponi (golumumab).

Interleukins (IL) are a group of signals active in the immune response. Three specific ones, IL-12, IL-23 and IL-17, all have been linked to psoriasis and psoriatic arthritis. Stelera (ustekinumab) works to interrupt both IL-12 and IL-23 pathways. Cosentyx (secukinumab) binds to the IL-17 protein and stops its ability to trigger inflammation.

Systemic Medications: Systemic medications are taken orally or by injection and work throughout the body. They usually are used for moderate to severe psoriasis and psoriatic arthritis.

Soriatane (acitretin) is a man-made form of vitamin A that helps control how fast skin cells grow and shed. Neoral (cyclosporine), originally used to prevent rejection in organ transplants, suppresses the immune system by slowing down the growth of immune cells called T-cells. Methotrexate, approved for treating severe psoriasis in the 1970s, slows down the growth rate of skin cells by binding to an enzyme triggering rapid growth. It also may calm down the overactive immune system.

Because of the risks associated with some older drugs, new oral medications have been developed. Otezla (apremilast) inhibits an enzyme known as phosphodiesterase 4, or PDE4, that helps control inflammatory actions within a cell.

Topical Treatments: Topical treatments are applied to the skin and usually are the first-line medical treatment for mild psoriasis. They are of no use in psoriatic arthritis.

Various vitamin-related products often are used to treat psoriasis topically and are available with a prescription. Dovonex (calcipotriene) is a synthetic form of vitamin D3 that works to slow skin cell growth, flatten lesions and remove scales. Taclonex combines calcipotriene with betamethasone dipropionate to slow skin cell growth, flatten lesions and remove scales while reducing itching and inflammation. Tazorec (tazarotene) is a form of vitamin A that slows skin cell growth. Vectical (calcitriol) is the naturally occurring active form of vitamin D3 and helps control excessive skin cell production.

Topical steroids come from naturally occurring corticosteroid hormones produced in your body that function to control inflammatory responses. They are the most frequently used treatments for psoriasis. There are seven different classes, the higher numbers indicating stronger medications. Steroid medications can be a tradeoff between better effectiveness and worsening side effects.

Complementary Treatments: Often used to treat mild or moderate psoriasis, phototherapy—or light therapy—exposes the skin to ultraviolet light on a regular basis under medical supervision to slow down the growth of skin cells. These treatments usually are given in a doctor’s office, psoriasis clinic or at home with a phototherapy unit. The use of tanning beds is controversial; the National Psoriasis Foundation does not recommend unsupervised treatments.

Complementary or herbal treatments include aloe vera, apple cider vinegar and oat baths. Currently, there is little scientific support for these interventions, and the existing support generally is mixed. However, many of these treatments can make skin softer and may relieve some complaints such as itching.

“There is interesting data coming out indicating a 10% or more loss in body weight, if body mass index is over 30, dramatically improves the response to TNF-blockers,” said Christopher Ritchlin, M.D., chief of allergy, immunology and rheumatology, Department of Medicine at the University of Rochester Medical Center in Rochester, N.Y. “Weight loss and exercise are more important than the choice of medication in some people.”

Treating Psoriatic Arthritis

Diagnosing psoriatic arthritis can be more difficult, particularly if you don’t have the skin disease.

“The diagnosis of psoriatic arthritis is largely made based on clinical symptoms,” said Wu. “Do you feel pain and stiffness in the morning that improves with activity? Are the joints swollen? Do you have back pain that improves instead of worsens with activity? The clinical history is the best way to decide what is going on.”

There are no specific blood tests to diagnose psoriatic arthritis. However, your doctor may order a test for rheumatoid factor to rule out rheumatoid arthritis (RA). Treatment options for psoriatic arthritis are largely the same as those for skin psoriasis. However, deciding which one to try can be difficult.

“You have to make treatment decisions balancing across five different domains,” said Ritchlin. “Decisions are based on the domains involved, the extent of pain, the amount of disability and other medical problems present.”

These domains are:

– the presence of skin disease;

– axial or spinal involvement;
– whether pain is on one side or both (asymmetric or symmetric);
– dactylitis, or “sausage digits,” inflammation/swelling of an entire finger or toe; and
– enthesitis at the site where ligaments or tendons insert into the bones.

There also are very important comorbidities that drive treatment decisions. Inflammation of the eye (uveitis), inflammatory bowel disease, fatty liver and depression all affect which medications will be used. Finally, the relative differences between the skin burden and the joint disease are other factors to consider.

“There really is no strict algorithm for treating psoriatic arthritis, given the great differences in both presentation and course,” said Ritchlin. “There is a lot of patient/doctor interaction in determining the best intervention.”

Treatment Options

Generally, the first treatment is a disease-modifying antirheumatic drug such as methotrexate or leflunomide. The former works well with the skin but has little scientific backing for use in joint disease. The latter is more joint-focused. The mainstay treatments are the anti-TNF alpha agents. These very expensive drugs are effective in all the domains and help prevent progressive damage.

The IL-23 inhibitors also have been very effective in treating the skin disease while being comparable to the anti-TNF alpha biologics in the joints. The PD-4 inhibitor class has modest effects on both skin and joint forms.

“The person’s insurance carrier also can have an impact, especially early on,” said Ritchlin. “Most rheumatologists and dermatologists prefer to start with the anti-TNF medications, but many insurers require we start with the cheapest alternatives and work our way up. As the cost of the drug skyrockets, even when the insurance company agrees to pay, many patients can’t afford the co-payments, which makes life really difficult.”

Treatment of the underlying condition also treats the pain.

“It is important to treat the underlying inflammatory disorder, rather than just the joint pain,” noted Wu. “If you don’t treat the disease, it can lead to destruction of the joint, resulting in deformities and disability. Taking a pain medication for the rest of your life takes care of the symptoms but not the problem.”

Currently, the general medical consensus is that patients have to remain on medications for the rest of their lives. However, some early studies, if confirmed, suggest some people might be able to stop taking their medications.

Treatments for skin and joint disease a decade ago were largely based on what worked with RA. Researchers have learned a great deal over the last 10 years, increasing our understanding of the pathways, the differences in comorbidities and how drugs work differently than in RA.

“We will find psoriasis is a curable disease with only one agent, although I don’t yet know what that agent will be,” said Ritchlin. “Psoriatic arthritis is going to be much harder, since those drugs that knock down psoriasis have only a 60% or so response rate in joint disease. However, I think responses significantly greater than those we are seeing now are within our reach.”

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Kurt Ullman, RN, is an Indiana-based medical writer whose career spans 30 years.

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