While psoriasis and psoriatic arthritis (PsA) have previously been thought to affect only the skin and joints, research in the past few decades has shown that psoriatic disease can impair the entire body, from the inside out.
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As an autoimmune disorder, psoriatic disease causes cells in the body to attack other cells.
Dermatologist Anthony Fernandez, MD, PhD, says psoriasis is a systemic disease, and psoriatic arthritis is one potential systemic aspect that can progress quickly. Without early treatment, it can cause significant and irreversible damage to bones and cartilage.
One of the challenges is that diagnosing psoriatic arthritis can be difficult because there are no blood tests that can deliver results telling whether a patient has this problem. Fortunately, there is emerging data suggesting that such tests may be available in the near future.
“Until then, we need to rely largely on clinical signs and symptoms to make a diagnosis,” Dr. Fernandez says. “We often work with our rheumatology colleagues to both secure a diagnosis of psoriatic arthritis and to choose the optimal treatment regimens.”
Symptoms are often slow to show
According to Dr. Fernandez, the majority of people who develop psoriatic arthritis have psoriasis first.
Up to 30 percent of people with psoriasis will develop PsA, but that can take an average of 10 to 12 years after the skin disease appears. It is not known exactly why the condition takes so long to appear, he says.
Busting a myth
Doctors previously believed that if PsA didn’t appear within 10 years of a psoriasis diagnosis, it wouldn’t occur at all. Recent studies, though, have revealed that the risk of developing PsA does not decrease over time for those who have psoriasis.
Ultimately, Dr. Fernandez says, diagnosing psoriatic arthritis as soon as possible is the key to successfully managing it.
“Early diagnosis is important to maximize chances that the proper medications are started,” he says. “That will protect quality of life and joint function.”
Treatments target markers in the blood
Generally, dermatologists treat mild psoriasis in patients without PsA with a topical cream or phototherapy that only penetrates the top skin layers.
However, for someone who has PsA and/or moderate to severe psoriasis, pills or injected medications — often biologics — are needed to control systemic inflammation. There are now many treatment options that effectively control psoriasis inflammation in both the skin and joints.
“Topical medications have no way to control systemic inflammation,” Dr. Fernandez says. “That’s why pills and injectables are so important. They can access the bloodstream and can reduce inflammation all over the body.”
While glucocorticoids are a help, injecting them can carry a small risk of serious joint infection, and side effects make long-term use undesirable. Your doctor will likely screen for active infections or a history of frequent infections when deciding whether to use this therapy.
Some pills may stimulate liver inflammation. They can also reduce blood counts or impair kidney function, he says.
Early signs of psoriatic arthritis
Some of the symptoms of PsA are similar to those of osteoarthritis and rheumatoid arthritis.
If you have psoriatic arthritis, you could experience:
- Joint swelling
- Limited range of motion
- Stiffness, especially in the morning or after long periods of inactivity
- Swelling of an entire finger or toe in the absence of trauma
- Lower back pain
- Silver-gray scaly spots on the elbows, knees, scalp and lower back
- Pitting or detachment of fingernails and toenails
If you see these signs, alert your dermatologist. He or she can tell you whether you should see another specialist, such as a rheumatologist.