Psoriatic Arthritis vs. Rheumatoid Arthritis: What Are the Differences?

Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are two types of inflammatory arthritis that are often mistaken for each other because of their similarities.

Both are considered autoimmune diseases where the immune system attacks the joints leading to pain, swelling, and stiffness. Inflammation from both conditions can also damage your blood vessels, skin, eyes, and other organs.

Even though they share some similar characteristics, they are very different conditions, and their differences are well-defined. Knowing the differences between PsA and RA can help you better understand your treatment options and what to expect as you live with and manage the condition that affects you.

This article will discuss the differences and similarities of PsA vs. RA, including symptoms, causes, treatment, and more.

Symptoms

In people with PsA, the immune system attacks the joints and skin. As a result, it causes joints to swell up and become painful. It also causes the body to overproduce skin cells, which leads to an inflammatory skin condition called psoriasis. PsA is seen in 30% of people with psoriasis.

With RA, the immune system attacks the linings of the tissues around the joints called the synovium. When synovial tissue is attacked, affected joints become severely inflamed and painful. Ongoing inflammation, over time, leads to the joints becoming damaged and deformed.

Both PsA and RA cause synovitis, or inflammation of the synovial membrane.

Symptoms of PsA

PsA affects 0.06% to 0.25% of American adults and 3.6 to 7.2 per 100,000 people worldwide. According to the National Psoriasis Foundation, PsA can either develop slowly with mild symptoms or quickly and become severe.

Common symptoms of PsA include:

• Fatigue
• Dactylitis: A condition that causes the fingers and toes to become so swollen they might resemble sausages
• Stiffness, pain, swelling, tenderness, and throbbing in one or more joints
• Skin lesions caused plaques
• Tenderness, pain, and swelling of the tendons, the strong, flexible tissues that connect muscle to bone
• Reduced range of motion of one or more joints
• Morning stiffness of joints
• Nail changes: Including nail pitting and nailbed separation
• Uveitis: Redness and pain of the eye
• Back pain
• Chest and rib pain

Symptoms of RA

Rheumatoid arthritis affects 1% of the world's population. In the United States, it is believed that 1.3 million Americans suffer from RA.

RA is a systemic disease, which means it affects the whole body. In addition to attacking the joints, RA also attacks the organs, such as the lungs and heart, and other tissues, including muscles, cartilage, and ligaments. Chronic inflammation and swelling from RA can become severe and lead to permanent disability.

Additional symptoms of RA include:

• Fatigue
• Low-grade fever
• Joint pain and swelling
• Pain and stiffness lasting for 30 minutes or more in the morning and after sitting for long periods
• Reduced range of motion of affected joints
  
• Anemia
• Weight loss
• Rheumatoid nodules: Firm lumps that appear below the skin, primarily in the elbows, hands, or ankles
• Dry, inflamed eyes that might be sensitive to light and cause trouble seeing properly
• A dry mouth and inflamed gums

Differences In Symptoms

There are some telltale signs that your arthritis symptoms are either due to PsA or RA:

• Asymmetrical vs. symmetrical: PsA is typically asymmetrical, meaning it affects different joints on different sides. RA, on the other hand, is symmetrical, which means it affects joints in matching pairs on both sides of the body (such as both wrists or both knees)
• Low back pain: PsA often causes inflammation of the lower spine, while RA less frequently affects the spine.
• Inflammation of the joints closest to the fingernails: PsA frequently affects the distal joints, located at the tips of the fingers where the fingernails start. With RA, the metacarpophalangeal joints (the joints that connect the fingers to the hands) are more commonly affected.
• Enthesitis: PsA can cause inflammation and pain in the areas where tendons attach to bones, a symptom called enthesitis. This type of inflammation is commonly seen in the heels, the bottom of the feet, and elbows.

Can PsA and RA Co-Exist?

It is possible to have both PsA and RA, but it is extremely rare. It is more likely for PsA or RA to exist with fibromyalgia or gout. RA might also co-exist with psoriasis.

There are very few prevalence studies on the co-existence of PsA and RA. One study reported in 2019 in the journal Therapeutic Advances in Chronic Disease found the prevalence of RA among people with psoriatic disease (PsA or psoriasis, or both) was 1.02%.

Causes

Researchers don’t have a solid understanding of what causes autoimmune diseases like PsA and RA, but there are some shared characteristics among the people who develop these conditions, including genetics and stress.

PsA Risk Factors

PsA most frequently affects adults in middle age, but it can develop in anyone regardless of age, including children. PsA affects men and women equally.

Risk factors for PsA are:

• Having psoriasis: The highest risk for PsA is in people who already have psoriasis. However, it is quite possible to have PsA without psoriasis or have psoriasis and never develop PsA.
• A family history: A family history of psoriasis or PsA increases the risk for PsA. A child whose parent has PsA, or psoriasis, might have a greater risk for developing PsA.
• Smoking: Researchers are unsure what the exact role smoking plays in the development of PsA. What they do know is that smoking is linked to oxidative stress, which can stimulate chronic inflammation.
• Environmental factors: A common theory about autoimmune diseases, and PsA, in particular, is that inflammation starts in response to an environmental trigger. This includes events like injuries, heavy lifting, infectious diarrhea, and infections that require hospitalization, and the Koebner phenomenon (the appearance of skin lesions on previously unaffected skin due to a skin trauma).
• Obesity: Numerous studies support an increased risk for PsA among people who are overweight. Studies have also found that PsA disease activity and medication response can improve with weight loss.
• Alcohol: While the research is mixed, excessive alcohol consumption might be a risk factor for the development of PsA.

RA Risk Factors

Much like PsA, the exact causes of RA are unclear, but researchers believe that certain risk factors increase your risk for the condition:

• Genetics: Having a family history of RA might mean a higher risk for developing RA. However, family history alone isn’t enough and a range of environmental and genetic factors are likely to contribute.    
• Hormones: Women are two to three times more likely to have RA than men. Researchers believe certain hormones in both genders play a role in triggering the disease, including high estrogen levels and low testosterone in females. In addition, menopause might also increase the risk of developing RA.
• Age: RA can affect anyone regardless of age but a person’s risk increases with age, especially after age 60.
• Smoking: Smoking is the strongest environmental risk factor for RA and multiple studies estimate the risk increases 30% for smokers. Smoking is also linked to more severe disease and smoking may even reduce the effects of medications used to treat RA.
• Stress: Some researchers believe the way the body responds to chronic stress plays a role in the development of RA. A 2021 study found people with early RA were reporting more stressful life events in the year before the start of symptoms. Cumulative stress seemed to have the most effect on the females.
• Obesity: Many studies have found a connection between being overweight and RA. One 2017 report in PeerJ discussing RA risk factors noted that 66% of people with RA are overweight. Excess weight has a destructive effect on the joints while fat promotes inflammation and the disease process.
• Diet: An unhealthy diet can increase the risk for many diseases and some researchers have suggested that certain substances in foods can trigger the development of RA.
• Previous infections: A 2013 report noted infections that might lead to RA are those that cause the immune system to lose its ability to fight off bacteria or a virus, trigger antigens that cause the immune system to become overactive, or cause the immune system to attack some of the body’s functions in response to the infection. Periodontal infections might also be linked to RA.
• Gut bacteria: Researchers have long looked for connections between gut bacteria and RA. A 2016 study found people with RA have more gut bacteria than people without the condition and that overabundance could predict the development of RA.

Diagnosis

PsA and RA share similar symptoms, which makes it important to get an accurate diagnosis from a rheumatologist, a doctor who has additional training and expertise in the diagnosis and treatment of conditions that affect the joints, bones, and muscles.

In diagnosing PsA, a rheumatologist will look at your skin and nails. If your skin has scaly patches and nail changes (pitting, flaking, nailbed separation, etc.), these are signs of PsA.

A rheumatoid factor (RF) blood test is an accurate way for a rheumatologist to make a diagnosis of RA. RF is a protein found in the blood of people with RA, and people with PsA will not have it.

Additional blood work that looks for specific antibodies linked to RA, such as anti-citrullinated protein (anti-CCP) and antinuclear antibody (ANA), can also help to distinguish RA from PsA.

Bloodwork is generally not helpful in making a diagnosis of PsA. This is because there is no specific gene linked to PsA and tests that look for inflammatory markers can show elevated levels in both RA and PsA.

HLA-B27, a genetic marker sometimes seen in PsA bloodwork, is also associated with a large group of autoimmune diseases called spondyloarthropathies. Only around 17% of people with PsA will test positive for HLA-B27.

X-rays are usually not helpful early on for either condition, but in the later stages, X-rays will show bone and joint changes.

If a rheumatologist can make a diagnosis using other diagnostic methods, they will generally hold off on other types of imaging studies, including magnetic resonance imaging (MRI) and ultrasound. However, they will utilize these tools if other diagnostic methods aren't helpful.

PsA and RA are both known for causing severe joint damage, especially if left untreated. If you suspect you have PsA or RA, you should see your doctor and get a diagnosis. It can be difficult to determine which condition is causing your symptoms, so your primary doctor will likely refer you to a rheumatologist for further testing and evaluation.

Treatment

The main goals of treating PsA and RA are the same—to reduce symptoms and improve quality of life. Aggressive treatment is vital because both conditions can be very painful and life-altering.

RA is a very destructive type of inflammatory arthritis, especially if it is not properly treated. And while PsA doesn’t present in the same way, it can behave aggressively, become extremely painful, and present treatment challenges.

A study reported in 2015 in the journal PLoS One found the overall pain and fatigue reported by people with PsA was significantly greater than what was reported by people with RA.

The treatment for PsA and RA tends to be similar. Treatment typically aims to slow disease progression and stop inflammation before it causes significant damage to the body.

Treatment for both PsA and RA might include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) to bring down ongoing inflammation and reduce pain
• Corticosteroids to manage flare-ups and periods of high inflammation
• Conventional disease-modifying antirheumatic drugs (DMARDs) to manage inflammation, alleviate symptoms, and slow down disease progression
• Biologic DMARDs, which target specific parts of the immune system
• Janus kinase (JAK) inhibitors calm the immune system and prevent joint damage.
• Physical therapy to help you keep moving safely
• Lifestyle therapies, including diet and exercise to help you maintain mobility and improve your quality of life
• Surgery to repair, replace, or stabilize damaged joints

If a person with PsA is experiencing skin symptoms, topical medicines, including corticosteroid and anti-inflammatory creams, can help reduce skin lesions and treat itching and pain.

There is no cure for PsA or RA, but most people with these conditions can manage pain and discomfort and have good quality lives. Make sure you follow all treatments as prescribed and attend regular follow-up appointments with your rheumatologist or other treating physician.

Prevention

Autoimmune diseases, like PsA and RA, generally are not preventable. If you have a family history of PsA, RA, or other autoimmune diseases, ask your doctor to help you identify any additional risk factors for developing these conditions.

Doctors do not know how to prevent PsA, and there is no specific treatment that can keep someone with psoriasis from developing PsA. There is also no way to identify people with psoriasis who might be at risk for PsA.

A 2019 review in the journal Nature discussed the challenges doctors face as they try to identify people with psoriasis who might be at risk for PsA. The report’s authors cite difficulty identifying events that might trigger PsA to develop or which groups of people these might affect.

One day, there might be more answers, but for now, doctors focus on managing symptoms of psoriasis before it progresses to severe disease and significantly increases your risk for PsA. People with PsA usually start to experience symptoms around 10 years after they get psoriasis.

There is no available treatment or other intervention to prevent RA or for doctors to know who might develop the condition. Researchers don’t know why some people with risk factors and family history don’t develop RA while others without known risk factors do.

They know that the disease is linked to different triggers that, in addition to risk factors, can lead to the development of RA. Some risk factors and triggers cannot be prevented, such as age, gender, and family history.

Other risk factors like smoking, diet, and exposure to environmental pollutants can be managed to potentially reduce your risk for RA. But even with managing risk factors, there is always a possibility you might still get RA.

Anyone with concerns about their risk for PsA or RA should speak to their doctor about managing risk and testing for inflammatory arthritis to potentially get ahead of serious problems.

Summary

Psoriatic arthritis and rheumatoid arthritis appear to have many similarities, especially symptoms. Both are linked to family history and can be treated similarly.

Specific symptom differences include the joints involved in PsA versus RA and the fact that PsA is linked to psoriasis. Additional differences exist in how PsA and RA present, are diagnosed, how they might progress, and how aggressively they should be treated.

Both PsA and RA are lifelong conditions, but they are manageable and treatable. Neither condition is preventable. If these conditions run in your family, talk to your primary care doctor about any risk factors you may have and reach out to your doctor if you experience symptoms of either condition, including joint pain and chronic fatigue.

A Word From Verywell

If you are diagnosed with psoriatic arthritis or rheumatoid arthritis, you should regularly check in with your rheumatologist. If either condition goes untreated, significant joint damage can occur, which could mean surgery or disability down the road.

PsA and RA can also put you at risk for other conditions, including heart disease, so it is important to talk to your doctor about symptoms and preventive measures. With the help of your rheumatologist and other specialists, you can manage PsA or RA and their effects. This should improve your quality of life and your prognosis.