From healthcentral.com
While both these conditions involve your joints, some key points of distinction can help you tell them apart
Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are both chronic inflammatory diseases that impact the joints. Telling the conditions apart can be challenging, but there are differences between the two that a trained eye can detect, says Laura Coates, Ph.D., an associate professor and researcher of psoriatic arthritis at the University of Oxford in England. Psoriatic arthritis is characterized by joint inflammation and often includes skin psoriasis. Meanwhile, rheumatoid arthritis is characterized by joint inflammation that affects multiple joints, often in a symmetrical fashion (i.e., both knees or both wrists).
How else are they similar and different? Let’s take a closer look at the ways these conditions overlap and what makes them unique.
Psoriatic Arthritis or Rheumatoid Arthritis?
The presence of psoriasis, an inflammatory skin condition, is often a clue that points to psoriatic arthritis rather than RA. Psoriasis occurs before the development of psoriatic arthritis in about 85% of patients.
There is also a gender gap between the two conditions: Psoriatic arthritis affects men and women equally, while more women than men develop rheumatoid arthritis, according to the Arthritis Foundation. Other key differences to look for include symmetry of symptoms: RA affects the hands, knees or ankles, and usually the same joint on both sides of the body (both hands as an example). RA is more common than PsA, affecting approximately one million people in the U.S., while psoriatic arthritis impacts roughly half that.
Meanwhile, although PsA symptoms differ between patients, peripheral joints are often involved, such as the fingers and toes. Back involvement is commonly associated with psoriatic arthritis (up to 70% of the time), and nail issues are often present. Dactylitiis, the swelling of a finger or toe, would also point to psoriatic arthritis. And unlike the symmetry of RA, PsA typically attacks joints on one or the other side of the body.
Key differences between rheumatoid arthritis and psoriatic arthritis include:
Rheumatoid Arthritis (common with RA but not PsA):
Symmetrical joint involvement
Cervical spine involvement (neck)
Interstitial lung disease
Rheumatoid Factor Positive
IL-6 driven (inflammatory pathway)
HLA-DRB1 alleles (genetic link)
Psoriatic Arthritis (common with PsA but not RA):
Psoriasis
Distal joint involvement
Asymmetrical joint involvement
Axial spine involvement
Enthesitis
Dactylitis
Nail involvement
IL-17A-driven (inflammatory pathway)
IL-12/23-driven (inflammatory pathway)
HLA-B27 alleles (genetic link)
How or why someone develops rheumatoid arthritis or psoriatic arthritis is not completely understood, but there are a few strong ideas. A combination of genetics and the environment is believed to play a role in both diseases. According to research in the journal Rheumatic and Musculoskeletal Diseases, one theory of how rheumatoid arthritis comes to fruition is the development of lung inflammation first, typically prior to joint symptoms, with the accompanying production of antibodies to citrullinated protein antigens. The gut and associated microbes are suspected of initiating psoriatic arthritis, according to the same source.
Family history, smoking or a viral infection may also play a role in the pathogenesis of both conditions. No matter the initial causes, both diseases trigger high amounts of inflammatory proteins (called cytokines) that are associated with joint pain and damage.
Comparison of Symptoms
In addition to the specific joints involved and symmetrical versus asymmetrical symptoms, there are other ways your doctor may be able to tell PsA for RA. According to Coates, tell-tale signs your doctor may look for include:
Psoriatic arthritis indicators:
RF and anti-CCP seronegative blood tests
Inflammatory markers often normal
Absence of rheumatoid nodules
Asymmetric oligoarticular manifestations
Predilection for the distal interphalangeal joints
Radiologic damage
Spinal issues (in about 50% of cases)
Skin manifestations (psoriasis)
Rheumatoid arthritis indicators:
RF and anti-CCP seropositive blood tests
Inflammatory markers usually raised
Rheumatoid nodules present over bony prominences
Symmetrical polyarticular manifestations
Typically affects the metacarpophalangeal and proximal interphalangeal joints
Radiologic changes
Spine is largely unaffected
Skin manifestations are atypical
To determine if you have either condition, your provider will usually begin with a physical exam. If multiple joints are inflamed and are predominantly symmetric, this may indicate rheumatoid arthritis. Joint involvement is often, but not always asymmetric in psoriatic arthritis (the right elbow and left knee may be painful).
Your provider will also be on the lookout for which joints are impacted: RA typically affects the shoulder, elbow, wrist, hip, knee, ankle and foot joints. In psoriatic arthritis, the joints of the hands and feet, large joints of the lower extremities, the axial spine and sacroiliac joints are commonly affected. If you have back pain, where the back hurts may also be an important clue. Back pain is usually not present in rheumatoid arthritis other than cervical spine pain (pain in the neck region).
There may be other clues to differentiate the two conditions that are important in the diagnosis process. Dactylitis, inflammation of the entire finger or toe, can be common with psoriatic arthritis. Dactylitis impacts psoriatic arthritis patients up to 50% of the time, compared with approximately 5% of patients with rheumatoid arthritis.
The presence of nail disease may also help your provider make a diagnosis. Up to 80% of people with psoriatic arthritis have some sort of nail changes. Nails may have pitting, discoloration, thickening, or the nail may be pulling away from the nail bed, as examples.
Blood tests may also help your doctor with a diagnosis. Approximately 80% of people with rheumatoid arthritis test positive for rheumatoid factor (RF) and about 60% to 70% have antibodies to cyclic citrullinated peptides (CCP), according to the Cleveland Clinic. RF and CCP are absent in most individuals with psoriatic arthritis.
Different types of imaging tests may also be required. For example, x-rays may be used to look for changes to the bones, such as new bone formation related to psoriatic arthritis. Magnetic resonance imaging (MRI) or an ultrasound test may help your doctor look at soft tissue issues, such as enthesitis that may also be related to psoriatic arthritis or tenosynovitis (inflammation around the tendon) which may indicate rheumatoid arthritis.
To aid in your diagnosis, your doctor will also collect information about your family’s medical history. If a parent or sibling has psoriatic arthritis, that greatly increases your chance of developing psoriatic arthritis, with a recurrence rate between 30% to 55%, according to the Journal of Rheumatology. On the other hand, while there is a family risk associated with rheumatoid arthritis, genes only slightly increase the risk. Environmental factors are likely to play a stronger role, according to the American College of Rheumatology.
Even with an experienced provider, differentiating between the two conditions isn’t easy 100% of the time, says Coates. “Typical rheumatoid arthritis and typical PsA are quite different, but sometimes there are ‘gray’ cases in the middle that confuse us and can be tricky to separate,” she says.
Treating Rheumatoid Arthritis vs. Psoriatic Arthritis
Reducing inflammation and treating “upstream” symptoms of the diseases is the name of the game when deciding on treatment options for both rheumatoid arthritis and psoriatic arthritis, according to the journal Rheumatic and Musculoskeletal Diseases. Steroids or methotrexate are examples of medications that will reduce inflammation related to both conditions.
However, medications that target more downstream symptoms and that are more disease-specific are not effective for both conditions, says Joel Gelfand, M.D., a board-certified dermatologist and director of the Psoriasis and Phototherapy Treatment Centre at Penn Medicine in Philadelphia, PA. “Several medications are effective for psoriatic arthritis but not RA, biologics targeting IL-23 or IL-17 being some examples,” Dr. Gelfand explains. Similarly, a biologic targeting the IL-6 inflammatory pathway would be prescribed for rheumatoid arthritis and not psoriatic arthritis.
Interestingly, some of the medications approved for both conditions may be processed differently in the body based on the condition. For example, Dr. Gelfand and colleagues investigated the risk of liver disease in patients with psoriasis, psoriatic arthritis, and rheumatoid arthritis receiving methotrexate. They found that individuals with psoriatic disease were more susceptible to liver disease and methotrexate hepatotoxicity than were rheumatoid arthritis patients.
“There is the concept of the psoriatic liver, where the inflammation in psoriasis seems to promote fatty liver changes which could be aggravated by methotrexate,” Dr. Gelfand explains. “A variety of blood tests and imaging techniques are now available to detect liver fibrosis (scarring) before clinically significant liver damage occurs, so methotrexate can be used safely in most patients with psoriatic disease.”
Having Both?
Fortunately, the odds are great that you won’t get both conditions. According to Coates, “It’s hard to ever say ‘never’ in medicine but this is pretty much a no.” Sometimes, it just takes time to sort things out, she says. “I saw one patient who was originally diagnosed with PsA and psoriasis and had psoriatic arthritis-type pattern disease but then after a few years he developed new rheumatoid antibodies (that were definitely negative before) and his arthritis changed.”
Takeaways
Both rheumatoid arthritis and psoriatic arthritis are similar and overlapping because both are inflammatory conditions that impact joints. There are important differences between the two diseases, and it is important to get to an experienced healthcare provider such as a rheumatologist who is familiar with the subtleties of each. Early detection and treatment for both is mission critical. The quicker a correct diagnosis is made, the sooner treatment can begin and remission achieved.
No comments:
Post a Comment