Both are the result of an overactive immune system—but some of their symptoms and risk factors can be quite different.

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People often use an arthritis diagnosis as an umbrella term to mean any kind of painful joint condition, but there are actually several different kinds of arthritis across a few different "families," so to speak.

While some forms of arthritis, like osteoarthritis, are degenerative, occurring with age, wear and tear, or injury, there are two types that are autoimmune (i.e. a condition where your immune system mistakenly attacks your own healthy cells): rheumatoid arthritis (RA) and psoriatic arthritis (PsA).

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Credit: Getty Images

But even though RA and PsA are both autoimmune diseases, they are still two different conditions with their own causes, symptoms, and treatments. Here's what you need to know about the similarities and differences between these two rheumatic conditions.

What's the difference between psoriatic arthritis and rheumatoid arthritis?

RA and PsA are both inflammatory conditions that affect people in the same age group (between 30 and 60 years old) and are often symmetrical, which means symptoms affect the joints on both sides of the body, rheumatologist Vinicius Domingues, MD, medical advisor to CreakyJoints, tells Health. Both conditions are also the result of an overactive immune system—one where your body attacks the joints and causes pain, stiffness, and swelling.

Many symptoms are the same between the two diseases—and treatments often overlap as well—but the main difference is where those symptoms are located. People with PsA, for example, often have symptoms in the distal joints of their fingers and toes, whereas people with RA suffer in their middle joints. PsA also affects more than just your joints, often attacking your eyes, skin, nails, and tendons.

What are the causes of psoriatic arthritis and rheumatoid arthritis?

We don't have an understanding of what causes many autoimmune conditions, including RA and PsA, but there are common links among people who develop these diseases.

"We don't know exactly what causes RA or PSA, but we do know there are genetic components and stress components to both," Magdalena Perez-Rivera, MD, rheumatology specialist with Conviva Care Centers tells Health.

Here are some of the primary risk factors for RA and PsA—you'll see there is a good amount of overlap.

Risk factors for psoriatic arthritis

  • Psoriasis (about 30 percent of people with this inflammatory skin condition go on to develop PsA)
  • Genetics
  • Stress
  • Smoking
  • Infections (bacterial or viral)
  • Obesity

Risk factors for rheumatoid arthritis

  • Genetics
  • Stress
  • Gender (RA is more common in females)
  • Smoking
  • Poor dental health
  • Hormones changes or abnormalities
  • Obesity

How do the symptoms of psoriatic arthritis and rheumatoid arthritis compare?

The symptom profile for these two arthritic conditions is actually where they differ the most. Although joint pain, stiffness, and swelling are the most typical symptoms for both RA and PsA, that's where their similarities end—and even with that, the way joint symptoms are experienced can be pretty different.

Symptom RA PsA

Rash

Sometimes; nodules and vasculitis

Yes, if you have psoriasis; itchy, red patches and/or thick, painful scales

Joint pain

Yes; most often in middle joints; often starts in fingers and toes, then moves to knees, hips, ankles, etc.

Yes; most often in distal joints of fingers and toes

Joint swelling/stiffness

Yes; may be worse first thing in the morning

Yes; joint swelling in fingers and toes can cause "sausage digits"

Fatigue

Yes

Yes

Back pain

Sometimes

Yes; can be severe and may spread into pelvis

Tendon inflammation

No

Yes; enthesitis is common in the areas where tendons connect to bones

Changes to nails

No

Yes; pitting, flaking, and separation of the nail from the nail bed

Symmetrical

Yes

Yes, but can also be asymmetrical

Changes to eyes/vision

Yes; uveitis is common

Yes; uveitis is common

How are psoriatic arthritis and rheumatoid arthritis diagnosed?

Unfortunately, there's enough overlap between these two conditions that diagnosis can be a little difficult, though a doctor may be able to know right away which kind of arthritis is affecting their patient.

For example, Dr. Domingues notes that the distal joints (i.e., the ones closest to the tips of your fingers and toes) aren't affected in RA, so asking a patient about where they experience pain can be a useful tool. Likewise, if a patient has diagnosed psoriasis or crumbling, pitting nails and visits their doctor complaining of new joint pain, they probably have PsA, not RA.

Just as often, however, further testing is needed to truly determine whether the cause of symptoms is RA or PsA.

"The good thing about RA is there are blood tests that can help us diagnose, but they aren't terribly helpful with psoriatic arthritis," says Dr. Domingues. "There's no gene or blood test for PsA, but inflammatory markers can be elevated in both conditions."

Radiology can also be helpful for diagnosing both conditions, Dr. Domingues explains: "Both x-rays and MRIs can allow us to see inflammation and bone issues [for RA and PsA]."

What does treatment look like for psoriatic arthritis and rheumatoid arthritis?

The main treatments for autoimmune arthritis conditions generally work for both RA and PsA; Dr. Domingues says most of the medications are used interchangeably and that non-pharmaceutical treatments, like physical therapy, also work well for both types.

Pharmaceutical treatments for RA and PsA:

  • Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen
  • Corticosteroids like prednisone
  • Disease-modifying anti-rheumatic agents (DMARDs) like methotrexate and hydroxychloroquine
  • Biologics, a more advanced type of DMARD that can stop or slow inflammation; these include Tumor Necrosis Factor-α (TNF) inhibitors and interleukin inhibitors (this is also where treatments for PsA and RA diverge a bit, with a few specific inhibitors working well for PsA but not RA and vice versa)

Non-pharmaceutical treatments for RA and PsA:

  • Physical therapy
  • Low-impact exercise
  • Smoking cessation
  • Topical analgesics
  • Ice and heat
  • Surgery

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