Autoimmune conditions cause the body to mistake its own tissues for foreign invaders, rallying inflammation-causing chemicals, including cytokines, to the defense. But while the mechanisms are the same, there are still many differences in how one autoimmune disease can affect your body versus another.

Such is the case with psoriatic arthritis (PsA) and lupus (also known as systemic lupus erythematosus, or SLE). Both are autoimmune diseases, and both share symptoms like joint pain, fatigue, and stiffness.

But these are two very different conditions that have their own causes, diagnosis, and treatments.

“The types of cytokines that are active in lupus and psoriatic arthritis…behave in different ways,” says Philip Mease, M.D., a clinical professor of rheumatology at the University of Washington School of Medicine and the director of rheumatology research at the Swedish Medical Center in Seattle, WA. This, in turn, causes different symptoms for those with either disease.

For example, lupus and psoriatic arthritis can both cause joint pain and stiffness, but “arthritis in a person with lupus isn’t a process whereby cartilage and bone are destroyed [as it is with psoriatic arthritis],” says Dr. Mease.

Similarly, lupus and psoriatic arthritis can also cause symptoms that appear on the skin. But while people with lupus can develop a specific type of rash called a malar rash that spreads across the nose and cheeks, those with psoriatic arthritis can develop psoriasis lesions that appear on the elbows, knees, and scalp, adds Dr. Mease. People with lupus have “a quite different type of rash than the psoriatic plaque,” he says.

Those aren’t the only differences you’ll find with PsA and lupus. Let’s take a look at how the two conditions can affect you, and how diagnosis and treatment options vary.

Lupus Symptoms

Symptoms of Lupus

Lupus tends to attack certain organs and tissues in the body, including the kidney, lungs, and brain, that psoriatic arthritis doesn’t, says Dr. Mease. According to the Centers for Disease Control and Prevention (CDC), symptoms of lupus include:

  • Abdominal pain

  • Blood clots

  • Chest pain, including when breathing deeply or lying down

  • Confusion and memory problems

  • Dizziness

  • Fatigue

  • Fever

  • Hair loss

  • Headaches

  • Joint pain, stiffness, and swelling

  • Pale or purple fingers or toes (from cold or stress)

  • Rash that appears on the nose and cheeks (i.e., a malar or ‘butterfly’ rash)

  • Scaly rashes

  • Sores in the nose and mouth, including the roof of the mouth

  • Swelling in the legs or around the eyes

  • Swollen glands

PsA Symptoms

Symptoms of Psoriatic Arthritis

Psoriatic arthritis is mostly known for causing joint pain and stiffness, but because it is a systemic disease, people with the condition can also develop other symptoms such as skin rashes and fatigue. According to the Cleveland Clinic, the most common symptoms of PsA include:

  • Discoloration or redness near the joints

  • Fatigue

  • Join pain and stiffness

  • Nail psoriasis (discoloration or pitting on the fingernails or toenails)

  • Pain and tenderness near where the tendons and ligaments attach to the bone, such as the back of the heel, where the Achilles tendon is located

  • Psoriasis rash (scaly, discolored patches on the skin, including the elbows, knees, and back)

  • Swelling in the fingers and toes (called dactylitis)

  • Uveitis (eye inflammation)

Causes of Lupus

What Causes Lupus?

It’s not exactly known what causes lupus, but researchers believe it’s triggered by a combination of a person’s genetics and their environment. For example, there are more than 30 genes that have been linked to the development lupus, per the National Library of Medicine (NLM). Many of these genes, including human leukocyte antigens (HLAs), are involved in the activation of the immune system.

It’s thought that lupus appears in people who harbor these genes when they come into contact with certain triggers, the most common of which include sunlight and infections (including Epstein-Barr), according to the Mayo Clinic. Sometimes, lupus can be triggered by exposure to some medications, including blood pressure and anti-seizure medications, as well as antibiotics, but in these cases, the symptoms usually disappear after people stop taking the drugs, according to the Mayo Clinic.

Causes of PsA

What Causes Psoriatic Arthritis?

As with lupus, it’s not clear what initially causes psoriatic arthritis, says Orrin Troum, M.D., a rheumatologist at Providence Saint John’s Health Center in Santa Monica, CA, but it’s possible that genetics and environment play a role here, too. Up to 50% of people with the condition also have a first-degree relative who has psoriatic arthritis or psoriasis, according to the NLM. Certain genes—including the HLA genes—have also been linked to joint damage and dactylitis associated with psoriatic arthritis, per NLM.

It’s thought that people who are predisposed to psoriatic arthritis develop the disease after coming into contact with an environmental trigger, such as an injury or infection, according to the Mayo Clinic.

Lupus Diagnosis

How Is Lupus Diagnosed?

There’s no definitive test that can diagnose lupus, so your doctor will likely rule out other causes of your symptoms first by taking a detailed account of your medical history and asking if anyone in your family has lupus (a family history increases a risk of the disease), according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).

Your doctor may also order some or all of the following tests:

  • Antinuclear antibody test (ANA) checks your blood for antinuclear antibodies, i.e., proteins in the immune system that target the body’s own healthy cells. Often, these antibodies are a sign that a person has an autoimmune disorder, according to the NIAMS, but some healthy people can also test positive for antinuclear antibodies.

  • Complete blood count is a test that checks for low platelets and low red and white blood cells counts (these numbers can be lower if you have lupus).

  • Erythrocyte sedimentation rate is a blood test that analyzes how fast your red blood cells settle to the bottom of a tube. If the sedimentation rate is too fast, it can indicate an inflammatory condition such as lupus (though other inflammatory disease can also be to blame).

  • Urinalysis examines a sample of your urine for high protein levels or elevated red blood cell counts—both of which can be a sign that lupus has harmed the kidneys, according to the Mayo Clinic.

  • Antibody tests: Anti-Sm antibody tests look for a specific antibody present in people with lupus; however, since this antibody is only in about 5% to 30% of people with the disease, testing negative does not rule out the condition. Anti-(double stranded)-DNA antibodies are also found in about 50% to 70% of people with lupus, although a high percentage of people will also never develop the antibodies.

PsA Diagnosis

How Is Psoriatic Arthritis Diagnosed?

As is the case with lupus, there’s no test that can definitively diagnose psoriatic arthritis. Rather, your doctor will likely start by taking a detailed account of your medical history; they can also check your joints for swelling and skin for signs of psoriasis, according to the NIAMS, which can help them narrow down the diagnosis.

To rule out rheumatoid arthritis (RA), another autoimmune disorder that can also cause swollen joints, your doctor may give you blood tests to check for certain antibodies (proteins made by the immune system to fight foreign invaders, such as infections) that tend to be elevated in people who have RA. These include the anti-CCP test (anti-cyclic citrullinated peptide antibody), which checks for the CCP antibody, as well as a rheumatoid arthritis factor test, which checks for the RF antibody, according to NIAMS.

However, there’s no definitive blood test for psoriatic arthritis like there is with rheumatoid arthritis, adds Dr. Troum.

Treatment Options

Treatment Options for Lupus and Psoriatic Arthritis

As chronic auto-immune diseases, there’s no cure for either lupus or PsA. However, treatments for both conditions can help you manage your symptoms and reduce inflammation.

Treatments for Lupus

Treatments for lupus have improved dramatically in the last few years, helping those with the condition to better manage symptoms of the disease, notes the NIAMS. These can include:

  • Non-steroidalanti-inflammatory drugs (NSAIDs) like ibuprofen (Advil, Motrin) and naproxen (Aleve) reduce pain and swelling.

  • Antimalarial drugs like hydroxychloroquine (Plaquenil) and chloroquine phosphate (Aralen) are also used to treat joint pain, skin rashes, fatigue, and lung inflammation.

  • Corticosteroids can help lower inflammation and reduce swelling, tenderness, and pain in the short-term.

  • Biologics limit the amount of abnormal B cells (cells in the immune system that create antibodies) found in people with lupus.

  • Immunosuppressive agents help suppress or curb an overactive immune system.

Treatments for Psoriatic Arthritis

Drug therapies for PsA continue to evolve, with medication options differing depending on the severity of your condition. They can include the following, per the NIAMS:

  • NSAIDs

  • Corticosteroids

  • Conventional disease-modifying anti-rheumatic drugs (DMARDs) help suppress an overreactive immune system

  • Biologics target specific immune messages, shutting down proteins that fuel inflammation

  • Janus kinase (JAK) inhibitors are a type of DMARD that also interrupts inflammatory cell pathways

Takeaways

Takeaways

Although psoriatic arthritis and lupus are both autoimmune diseases and share some of the same symptoms (including joint pain, joint stiffness, and fatigue), the two conditions have distinguishing features including the psoriasis rash that can appear in people with psoriatic arthritis and the butterfly rash that can develop in people who have lupus, says Dr. Troum.

What’s true for people with both conditions, though, is that no two people with either lupus or psoriatic arthritis will experience their disease in quite the same way. Sometimes, people with lupus and psoriatic arthritis will have active symptoms in multiple areas of the body, and other times, the disease will be limited to only one area of the body.

“I sometimes use an orchestral metaphor, where there are times when every section of the orchestra is playing at once,” says Dr. Mease. “And then there may be other times when just the piccolo section is playing or just the trumpets or the violins are playing… Everyone is going to have a slightly different mix of which [areas of the body] are involved, and when [their symptoms] might be active at a given time.”

This article was originally published August 12, 2024 and most recently updated August 20, 2024.
© 2024 HealthCentral LLC. All rights reserved.
Maria Masters, Health Writer:  
Brian LaMoreaux, M.D., Rheumatologist:  

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