By Rebecca Haberman, MD, as told to Stephanie Watson
Psoriatic arthritis and psoriasis aren't curable, but they are becoming more treatable. While not everyone can achieve clear skin or pain-free joints, things are improving with each new drug that we have to treat them with.
Our stable of drugs is growing exponentially, which is really important, especially in psoriatic arthritis, where one particular medication doesn't treat everyone with the disease.
The diagnosis of psoriatic disease has also come a long way. It was under-recognized for a long time. It's only been in the past 10 to 15 years that people have really begun to pay attention to it. Since then, it's become easier to diagnose it.
Psoriasis and Psoriatic Arthritis: The Overlap
For many of the people I treat, psoriasis and psoriatic arthritis coexist.
Nearly 90% of people with psoriatic arthritis have or will eventually get psoriasis. Over the course of their lifetime, up to 30% of those with psoriasis will get psoriatic arthritis.
Both are inflammatory diseases that start when the immune system misfires and triggers inflammation in the joints or skin.
About half of the time, these conditions run in families.
Doctors used to think of -- and treat -- psoriasis solely as a skin disease. Today we know that it, like psoriatic arthritis, is a body-wide condition.
Treatments for both aim to bring down inflammation all over the body.
Psoriatic disease can be tricky to treat because it shows up in so many ways. Inflammation can affect:
- Your joints
- Where tendons and ligaments connect to bone (called the entheses)
- Your fingers and toes
- Your spine
- Your skin
- Your nails
While we think of psoriatic disease as one condition, it is possible that the diseases that make it up are a little different.
So it makes sense that we need different medicines to treat it. Older disease-modifying antirheumatic drugs (DMARDs), like methotrexate, target overall inflammation to slow the disease and prevent joint and skin damage.
A newer group of drugs called biologics has more specific targets within the immune system. They block certain proteins in your immune system that trigger inflammation. There are a growing number of these treatable targets, including ones called:
- Tumor necrosis factor-alpha (TNF-alpha)
- Interleukin (IL) 12, 17-A, and 23
Trial and Error
No test can show which of these targets is best suited for you. So your doctor won't know which of these drugs will work best against your disease until you try it.
The severity of your disease and which parts of your body it affects most (skin, joints, etc.) will help determine which medicine the doctor gives you first. For example, IL-17, IL-23, and IL-12/23 inhibitors seem to work especially well against plaque psoriasis.
Also important is whether you have other medical conditions that might make one biologic riskier for you than another.
But overall, prescribing these drugs can involve some trial and error.
The ultimate goal is to put you into remission, where you have no symptoms. But if you've lived with the disease for a long time, less pain, fewer swollen joints, and fewer skin plaques may be more realistic things to shoot for.
The Future of Treatment
Today's treatments for psoriasis are more effective than the ones available for psoriatic arthritis. Thanks to the wide range of topical medicines, biologics, and other therapies, we can get almost 100% clearance of the skin much easier than before.
It's hard to achieve that with the joints. So we're trying to come up with new ways to make people feel better.
The outlook for psoriatic arthritis may change as companies discover new drugs and they become available. For example, guselkumab (Tremfya) became the first IL-23 inhibitor to be FDA-approved for psoriatic arthritis.
Drug companies are on the hunt for new ways to block inflammation in psoriatic disease. Some ideas involve combining biologics or targeting more than one inflammatory pathway at once. For example, a drug in development, bimekizumab, targets two inflammatory proteins, IL-17A and IL-17F. In studies, it helped some people's symptoms improve by as much as 90%.
Researchers are also working on more personalized approaches to diagnosing psoriatic disease.
The ultimate goal is to get to precision medicine, where I can do a blood test and say, “This is how the patient is presenting and this is the medication that's going to work.”
Rebecca Haberman, MD is a rheumatologist with NYU Langone Health in New York. She's also a clinical instructor at NYU's Grossman School of Medicine.