Psoriatic or Rheumatoid Arthritis: Which One Do You Have?

by Casey Nilsson Patient Advocate

Psoriatic arthritis and rheumatoid arthritis are two autoimmune diseases that share common symptoms of joint stiffness, pain, and damage. So how do you know what you have? Here are a few ways your physician can determine which condition you have.

Smiling adult daughter comforting her senior mother.

Family History of Psoriatic Disease

If a member of your family has psoriasis or psoriatic arthritis, there’s a chance you will, too. Up to 40 percent of patients with psoriatic arthritis have a positive family history of psoriatic disease.

Doctor assessing a patient's joint pain

Psoriasis and Joint Pain

If you already have psoriasis and you’re experiencing joint pain, you probably have psoriatic arthritis. About 30 percent of people with psoriasis will go on to develop psoriatic arthritis in their lifetime.

Woman getting a blood test

A Positive Rheumatoid Factor Blood Test

A blood test that detects your rheumatoid factor, or autoantibodies that attack healthy tissue, can help determine if it’s rheumatoid factor or psoriatic arthritis. About 80 percent of people with rheumatoid arthritis have a positive rheumatoid factor of 14 IU/ml or higher.

Blood test results

Other Possibilities of a Positive Blood Test

But a positive rheumatoid factor test isn’t conclusive. About 15 percent of the total population carries rheumatoid factor in their blood without ever developing rheumatoid arthritis. A positive rheumatoid factor can also indicate other diseases, including parasites, gout, or lupus.

Hand pain
Getty Images

Joint Pain Symmetry

About 50 percent of psoriatic arthritis patients experience joint pain symmetry, when pain in joints on the left side of the body also appears on the right side of the body. But joint pain symmetry isn’t definitive. People with psoriatic arthritis also experience joint pain asymmetry – i.e., a swollen joint in the right middle finger and spinal inflammation.

Swollen fingers

Sausage Fingers

People with psoriatic arthritis tend to experience whole inflamed digits called dactylitis, colloquially known as sausage fingers. Despite the nickname, dactylitis also affects the toes.

Hands with rheumatoid nodules.

Rheumatoid Nodules

People with rheumatoid arthritis will more often experience nodules, or firm lumps, atop swollen joints. People with psoriatic arthritis don’t often exhibit nodules atop swollen joints.

Damaged fingernails.

Nail Pitting

People with psoriatic arthritis also often experience nail symptoms including nail pitting, which are tiny pitted dots that can appear all over the nails. People with rheumatoid arthritis rarely experience nail pitting, so this is a strong indicator of psoriatic arthritis.

Young woman having a genetic test swab.

Genetic Testing

Researchers have discovered genetic markers that are specific to psoriatic arthritis and rheumatoid arthritis. For psoriatic arthritis, it’s HLA Cw6 and B27 or the interleukin 23 receptor, which is also present in people with irritable bowel syndrome and ankylosing spondylitis. For rheumatoid arthritis, it’s human leucocyte antigenDRB1.

Doctor showing woman electronic tablet.

If You Think You’ve Been Misdiagnosed

Get a second opinion from another rheumatologist or dermatologist. The bright side: Treatment for psoriatic arthritis and rheumatoid arthritis is often the same. For either disease, your doctor may prescribe a non-steroidal anti-inflammatory drug such as Motrin, an immunosuppressant like methotrexate, or any number of biologics on the market.

Casey Nilsson
Meet Our Writer
Casey Nilsson

Casey Nilsson, an award-winning journalist and magazine editor based in Rhode Island, writes about autoimmune disease for HealthCentral. Casey is a 2018 Association of Health Care Journalists fellow, and her reporting on unfair labor conditions for people with disabilities was a finalist for the City and Regional Magazine Association Awards. Diagnosed with psoriatic arthritis in 2016, Casey enjoys digging into rheumatologic news, research and trends.