RA or PsA: What’s the Difference?

Red-hot, swollen joints lead to excruciating pain.  Patients, writhing in agony, phone their doctors for help.  For the lucky, a quick diagnosis is made:  rheumatoid arthritis.  The luck is in the speedy diagnosis, not in the unfortunate diagnosis itself.

Often the diagnosis is unclear.  Doctors aren’t sure what the problem is, or even if there is a problem.  Alas, it’s not unusual for busy doctors to give hurting people in this situation the brush-off with, “It’s all in your head.”  If  your disease doesn’t match the pattern described in textbooks (atypical presentation), it’s hard for doctors to recognize.  Diagnosis of autoimmune disease can take years.

Even when a doctor determines that autoimmunity is the culprit, it might not be clear exactly which disease is causing the problem.  Many have very similar symptoms. Fortunately, arthritic diseases caused by a faulty immune system respond to similar medicines.  In order to get insurance to cover treatment, a diagnostic-label is sometimes affixed despite the uncertainty.  Over time, the uncertainty is forgotten and the tentative label takes on a life of its own.  Maybe it doesn’t matter.  After all, at least the patient gets treated.

Then again, maybe accurate diagnosis wherein different diseases are clearly distinguished would lead to better data about which medicines would be most likely to help a given patient.  It’s maddening to suffer through years of trial-and-error hoping to find effective treatment. When rheumatologists evaluate a new patient with autoimmune arthritis, one question is, “Is this rheumatoid arthritis, or is it psoriatic arthritis (or is it something else entirely)?”  Keys they look for are 1) nail involvement, and 2) skin psoriasis.  There is no nail involvement in RA.  In PsA, 80% of patients have nail symptoms such as ridges, grooves, and/or pitting.  Psoriatic finger/toenails can thicken instead of growing longer, sometimes even crumbling or falling off.  The problem with using nails as diagnostic criteria is that, according to the National Psoriasis Foundation, 20% of PsA patients do not have nail symptoms.  I propose that looking for ridged nails without asking about ridged nails is an exercise in futility, since people with unsightly nails might address the issue.  Furthermore, according to the American College of Rheumatology, “Psoriatic arthritis can occur in people without skin psoriasis, particularly in those who have relatives with psoriasis.”  In fact, in juveniles, up to half of PsA patients experience arthritis symptoms before there is any skin involvement.  Obviously we have a problem.

Dr. Irwin Lim, rheumatologist, writes:

Many patients labeled as having “Seronegative Rheumatoid Arthritis” or “Seronegative Inflammatory Arthritis” may have Psoriatic Arthritis.

In two short video clips, he explains more:

Not all patients with the diagnosis of psoriatic arthritis will have skin manifestations. Sometimes the diagnosis is made from a collection of other symptoms and signs, and a positive family history. Sometimes the rash actually occurs years after the development of psoriatic arthritis. So, it’s definitely possible to have psoriatic arthritis without the skin psoriasis.

Psoriatic arthritis can be very difficult to diagnose. It really does require the doctors to have a high index of suspicion. In patients who already have psoriasis affecting the skin or nails, the diagnosis is much easier because most people would think about it. But, sometimes, the symptoms can be quite vague. So many people have back pain, and it’s often explained away. In addition, joints aches and pains are common in the community, and sometimes the link with psoriatic arthritis is not put together. So, typically the diagnosis is made by an experienced physician taking into account the history, the examination, and the clinical context.

He is not alone in his views.  Doctors Jaya Philipose, MD and Atul Deodhar, MD write

The diagnosis of psoriatic arthritis (PsA) often is missed, partly because patients may present with inflammatory spinal pain, tendinitis, enthesitis, or dactylitis rather than a “true arthritis.”

It’s important to note that the rheumatologist is looking for clues at a single moment in time. In contrast, the patient knows a lifetime’s worth of history. If patients know the types of patterns that doctors are looking for, we can better provide the information that our doctors need to make an accurate diagnosis.

Usually doctors looking at family history are only interested in first-degree blood relatives:  parents, children, and full-siblings.  When considering psoriasis, though, doctors are also interested in second-degree relatives:  grandparents, grandchildren, half-siblings, aunts, uncles, nieces, and nephews.  Contact family members and ask.  Don’t just ask about psoriasis.  Ask about rashes and flakey skin.  Ask about severe dandruff — on the elbows and knees as well as on the scalp (not everyone is going to see a doctor for a diagnosis of those flakes).  See if  you can find a pattern.  Patterns can help your doctor make a diagnosis.

Following is a chart comparing some of the similarities and differences of RA & PsA:

PsAvsRA

For further reading:

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3 thoughts on “RA or PsA: What’s the Difference?

  1. Nice to hear from you socks. Hope you are well. Very interesting article. Makes me wonder about my diagnosis. I’m always seronegative but my anti-CCP is always positive and my CRP goes up and down like a roller coaster. I seem to have symptoms of both at times. Since I have never had skin involvement the doctor went with RA. I guess since they are treated the same the name doesn’t matter.
    Thanks for the information. I often think PSA gets little or no attention in the discussion about autoimmune disease and is less understood by the public than RA..

  2. Hi, Socks! What a nice surprise to see a new post from you! I’ve missed your “voice”.
    And what a very sharp, informative article. I know very little about PsA, really, except that it can cause painful arthritis along with skin problems.
    How are you? I hope you’ll post again soon and update us on how you’re feeling and how your family is doing. 🙂

    • Thank you 🙂 I’m medium, RA-wise.
      My mother-in-law fell and broke her hip. Nobody phoned us, so we learned when I saw it on Facebook. My sister-in-law passed away and I learned about it on Facebook. My favorite of my hubby’s uncles passed away and again, nobody phoned – I saw it on Facebook and lit into the person who had time to post but not time to inform family members. Really? Are today’s kids that clueless? Well, some of them were, but that gap in their etiquette education has been addressed. I know I got through to them, because they did not post a few weeks later when my husband’s aunt lost her (very short) fight with cancer.

      My boys are still in sports – I will post more about that another time. For now, suffice it to say that it’s keeping me very busy and we’ve lost the low-mileage discount on our auto insurance.

      I have a zillion ideas for blog posts, but haven’t had time to complete the research I need to do before writing.

      Hope you are doing well 🙂

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