In an earlier post I presented a guide to living with rheumatoid arthritis (RA). That’s all good if you have RA, but what if your rheumatologist diagnosed you with psoriatic arthritis? What’s psoriatic arthritis and how is it similar or dissimilar to RA? This week I’ll present to you Part 1 of a Guide to living with psoriatic arthritis. I’m going to present this as a three-part series. Part 1 will cover the basics: what is psoriatic arthritis, the cause, risks, symptoms, diagnosis, and treatment. In Part 2 I’ll cover prognosis, what to expect, diet and exercise. In Part 3, I’ll be covering the financial side of psoriatic arthritis: How to get access to medications and how to navigate the complicated world of health insurance.
What is psoriatic arthritis?
Psoriatic arthritis (PsA) is a type of autoimmune inflammatory arthritis that afflicts people who suffer from psoriasis (PsO). It’s estimated that about 26% of people who suffer from psoriasis will get psoriatic arthritis at one point during their lifetime. Typically, people develop psoriasis first and then get the arthritis. In some cases, people develop arthritis first and then get psoriasis but this is a lot less common. Psoriatic arthritis is one of the more common causes of autoimmune arthritis affecting about 2 to 3% of the population.
What is psoriasis and what are the different types of psoriasis?
Psoriasis is an autoimmune disease that affects the skin. It typically involves the elbows, knees, and scalp, but you can find it in many other areas. It typically causes itchiness, burning as well as a stinging sensation. Psoriasis affects about 2% of African-Americans and affects about 3.6% of Caucasians. Usually people develop it between the ages of 15 and 35, but it can also happen in very young children and older adults as well.
There are many different types of psoriasis and they are all associated with psoriatic arthritis.
- Plaque psoriasis
- Guttate psoriasis
- Inverse psoriasis
- Pustular psoriasis
- Erythrodermic psoriasis (life-threatening type of psoriasis)
Please follow this link to learn more about psoriasis.
What causes psoriatic arthritis?
Like most diseases in rheumatology, we’re not sure. We do know that there’s a strong genetic and environmental part to psoriatic arthritis. Here are some genetic associations.
- HLA-Cw6 is associated with severe early onset skin psoriasis
- HLA-B38 and HLA-B39 are associated with psoriatic arthritis
- HLA-B27 is associated with psoriatic arthritis that affects the spine.
Although genes do play a part in psoriatic arthritis, most people who have psoriatic arthritis have no genetic risk factors.
The Koebner Phenomenon
Have you ever heard of the Koebner phenomenon? This phenomenon describes a new skin lesion in an area where healthy skin was injured. For example, let’s imagine that you have psoriasis. A mosquito comes along and bites you, it itches, so you scratch. Then, about 10 days later, you notice that you’ve developed psoriasis in the area you scratched. That’s the Koebner phenomenon.
Now try to imagine the Koebner phenomenon involving joints. It’s thought that about 25% of people who get psoriatic arthritis develop the condition after trauma to a joint. We call this the deep Koebner phenomenon.
Ultimately, we still don’t know exactly why people develop psoriatic arthritis. Our best guess like most autoimmune diseases, is that certain people are born with a predisposition to develop both psoriasis and psoriatic arthritis. Then, something in the environment triggers the disease to “come online”.
Does everyone with psoriasis get psoriatic arthritis?
No. A recent Japanese study tried to find certain risk factors that predispose patients with psoriasis to develop psoriatic arthritis. First, they found that about 17% of people with psoriasis also had psoriatic arthritis. Second, they found that people who had psoriasis involving their nails had a higher chance of having psoriatic arthritis: 29% (PsO) versus 62% (PsA). Interestingly, they also found that people who had high uric acid levels also had a higher risk of having psoriatic arthritis 9% (PsO) versus 22% (PsA).
As a side note, when uric acid levels are high, this increases the risk of gout.
How does psoriasis affect the nails?
Nail psoriasis is very common. It ranges from about 50% to 87% of people who have psoriasis. Now, nail psoriasis can present in many ways depending on the anatomic site of the psoriasis inside the nail. First, a bit of anatomy.
The nail consists of the nail fold, the nail matrix, and the nail bed. The nail fold is where the blood vessels supplying the nail come from. They can be compromised in many diseases such as scleroderma. The nail matrix is responsible for formation of the nail plate and the nail bed is responsible for attaching the nail plate firmly in place.
When psoriasis affects the nail matrix. It can cause pitting, crumbling, white spots and red spots in the lunula. When psoriasis affects the nail bed, it can cause splinter hemorrhages and splitting of the nail from the nail bed (onychyolysis). Please click the following link to learn more about nail psoriasis + pics.
Please note that none of the features of nail psoriasis are exclusive to psoriasis. Other diseases can cause these, including:
- Reactive arthritis
- Alopecia areata
- Chemical dermatitis
- Pemphigus vulgaris.
- Incontinentia pigmenti
How is psoriatic arthritis different from rheumatoid arthritis?
Although both psoriatic arthritis and rheumatoid arthritis are both autoimmune diseases that affect joints, they are both distinct diseases. It isn’t simply because you have psoriasis and inflammation in your joints, that you have psoriatic arthritis. Many people with psoriasis have rheumatoid arthritis. Psoriatic arthritis and rheumatoid arthritis have their own pathophysiology, epidemiology, and symptoms. Although they do share many treatment options, they also have some medications tailor-made for them.
Here some of the main clinical differences between psoriatic arthritis and rheumatoid arthritis.
||MCP, PIPs, wrists, and MTPs
|Involvement of the spine
||Rare, involves the cervical spine
||RF and CCP antibody negative
||RF and/or CCP antibody positive
* RF = rheumatoid factor, CCP = Cyclic citrullinated peptide antibodies
As you’ll see later on, it’s a lot more complicated that. Many people presenting with psoriatic arthritis present almost exactly like rheumatoid arthritis. Here were a few other features that favor a diagnosis of psoriatic arthritis.
- Presence of nail pits
- When there is inflammation of the distal interphalangeal joints (Tip of your finger) without any evidence of osteoarthritis
- “Sausage digits” = dactylitis. This happens when the tendons that supply of the fingers and toes get inflamed.
- Any inflammation of tendons and ligaments, such as Achilles tendinitis and plantar fasciitis.
- When there is a family history of psoriasis or psoriatic arthritis, particularly in a first-degree relative. That mom, dad, kids and siblings.
- The spine is involved.
What are the symptoms of psoriatic arthritis?
If you’re experiencing joint pain and you have a history of psoriasis, particularly psoriasis that involves your nails, you need to think about psoriatic arthritis. So what do I mean by joint pain? When it comes to joint pain, what I really mean is, autoimmune or more specifically, inflammatory joint pain.
Psoriatic arthritis can affect almost any joint: knuckles, wrists, toes, knees, shoulders, elbows, hips, and the spine. Mechanical joint pain is very different from inflammatory joint pain. Let me explain.
Peripheral inflammatory joint pain
Peripheral joints include all joints except those involving the spine. When there is inflammation in a peripheral joint, typically people experience pain, swelling, and stiffness, particularly in the morning that lasts at least an hour. Sometimes they do see some redness and the joints may feel hot at times. Often times, people also feel a lot more tired than usual, and they can even run low-grade fevers.
Axial inflammatory joint pain
Axial joints are those that involve the spine. Inflammation involving the back causes symptoms that are very different from your usual mechanical back pain. Here are some of the following key characteristics:
- Back pain present for more than three months.
- Pain improves with exercise.
- Pain improves with anti-inflammatory medications like naproxen or ibuprofen.
- Rest usually worsens the pain.
- Back pain that wakes you up during the second half of the night.
- Pain and prolonged stiffness in the morning, typically lasting more than an hour.
- Alternating deep buttock pain.
Enthesitis means inflammation of connective tissue that attaches to bones. These include tendons, ligaments, and bursae. Most cases of enthesitis are caused by injury or overuse. Think of a marathon runner with Achilles tendinitis or a tennis player with tennis elbow. In psoriatic arthritis, the immune system attacks these connection points. So you can have someone who leads a fairly sedentary life with Achilles tendinitis on both feet, runner’s knee, and plantar fasciitis happening all at once, for no good reason. Not a pleasant experience.
Uveitis is a general term that we use to describe a group of inflammatory diseases that cause inflammation in many parts of the eye: uvea, lens, retina, optic nerve, and the vitreous. Depending on where the inflammation is happening, your ophthalmologist may describe it as anterior uveitis, intermediate uveitis, posterior uveitis, or panuveitis.
Uveitis is associated with many diseases including psoriasis and psoriatic arthritis. Sometimes uveitis is the first manifestation of psoriatic arthritis. This is why I’ve included this topic here, even though technically it isn’t arthritis. It’s important to know and keep in the back of your mind.
Patterns of disease
Just like rheumatoid arthritis, psoriatic arthritis, can manifest in many ways. For those of you who want to get really technical, I’ve included a table describing the most common ways psoriatic arthritis presents.
|Asymmetric oligoarticular* disease
||DIP joints and PIP joints of the hands and feet. MCP joints, MTP joints, knees, hips, and ankles.#
|Predominant DIP involvement
||DIP and PIP joints
||MCP joints, PIP joints, and wrists.
|Axial involvement only (spine)
||Sacroiliac joints, vertebral
||Tendons and ligaments
* oligoarticular = 2 – 4 joints
# DIP = distal interphalangeal joints, PIP = proximal interphalangeal joints, MCP = metacarpophalangeal joints, MTP = metatarsophalangeal joints
$ Mutilans = severely deformed
! Polyarthritis = 5 or more joints involved
How is psoriatic arthritis diagnosed?
We currently use the CASPAR criteria to make the diagnosis of psoriatic arthritis. You need three points to get the diagnosis because having 3 or more points has a 99% specificity and 92% sensitivity for the diagnosis of psoriatic arthritis. Obviously, there are exceptions as the CASPAR criteria are predominantly used for research purposes.
As you can see, you don’t need to have psoriasis to get a diagnosis of psoriatic arthritis. I know this sounds counterintuitive.
CASPAR classification criteria
- Evidence of psoriasis (current, past, family)
- 2 points if current
- 1 point if history of psoriasis or family history
- Psoriatic nail dystrophy = 1 point
- Negative rheumatoid factor = 1 point
- Dactylitis = 1 point
- X-ray changes = 1 point
Unlike rheumatoid arthritis, we do not have blood tests to help with the diagnosis of psoriatic arthritis. At times, your rheumatologist may order something called a HLA-B*27 test.
HLA-B*27 is a genetic test. The majority of people who have a positive HLA-B*27 are perfectly healthy. HOWEVER, having a positive HLA-B*27 can put you at increased risk of developing what we call spondyloarthritis-associated diseases. This is a family of autoimmune diseases. They include:
- Ankylosing spondylitis, now called axial spondylitis
- Peripheral spondyloarthritis
- Reactive arthritis
- Psoriatic arthritis
- Crohn’s disease
- Ulcerative colitis
Not every person with psoriatic arthritis will test positive for HLA-B*27, however, those that do, have a higher risk of having axial involvement. This is important to know, because it may affect the medication your rheumatologist recommends.
Is there a cure for psoriatic arthritis?
The simple answer to this question is no. Psoriatic arthritis is a chronic, lifelong disease. Although there is no cure for psoriatic arthritis, there are many medications that can help halt or slow down progression: disease modifying anti-rheumatic drugs (DMARD).
Cardiovascular disease and psoriatic arthritis
In recent years, scientists have found an association between cardiovascular disease and many autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, psoriasis, Crohn’s disease, ulcerative colitis, and psoriatic arthritis. Basically, people who suffer from psoriatic arthritis have a higher risk of developing cardiovascular disease.  Unfortunately, they also tend to have more traditional cardiovascular risk factors like high blood pressure, high cholesterol, and diabetes. On the upside, effective treatment of psoriatic arthritis can decrease this risk.
How is psoriatic arthritis treated?
Like rheumatoid arthritis, psoriatic arthritis is treated with disease modifying anti-rheumatic drugs (DMARDs). These medications are designed to stop or slow down the progression of psoriatic arthritis by targeting the faulty part of the immune system. Without treatment, psoriatic arthritis, can cause permanent damage to joints, tendons and ligaments leading to functional impairment and a decrease in quality of life.
Which DMARDs are used to treat psoriatic arthritis?
The following are some of the medications that doctors often use to treat psoriatic arthritis. Your doctor will recommend certain treatments based on the involved joints and organs, as well as severity, allergies, and other medical conditions you may have.
I’ve broken down the different medications into the following broad categories.
Nonsteroidal anti-inflammatory drugs
- Hydroxychloroquine (Plaquenil) – caution as this medication may make psoriasis flare
- Leflunomide (Arava)
- Azathioprine – rarely used for psoriatic arthritis
Tumor necrosis factor – alpha (TNF-alpha) inhibitors
- Certolizumab pegol (Cimzia)
- Etanercept (Enbrel)
- Adalimumab (Humira)
- Infliximab (Remicade)
- Golimumab (Simponi)
Interleukin 12 and 23 inhibitors
Interleukin 17 inhibitors
- Secukinumab (Cosentyx
- Brodalumab (Siliq) – not FDA approved for PsA
- Ixekizumab (Taltz) – not FDA approved for PsA
T cell inhibitors
Interleukin 23 inhibitors
Phosphodiesterase 4 inhibitors
To read more about treatment for psoriatic arthritis. Please follow this link.
Here in the US, we are starting to see biosimilar medications. These are medications that are sort of copied from existing biologic medications. They are NOT generic medications. The problem with biosimilars is that because of their complexity, it literally is impossible to exactly copy a biologic medication. If you want to learn more about biosimilar medications, please check this article.
Can I stop my medications if I’m feeling better?
No. Psoriatic arthritis is a life-long disease. If you’re feeling better, great! However, it’s probably your medications that are keeping you that way. If you stop your medications the psoriatic arthritis will likely come back. Psoriatic arthritis subsides spontaneously in a VERY small subset of people.
If your medication is making you feel sick, talk to your rheumatologist. They truly have your best interest at mind and they want to find the best treatment for you.
Do not stop your medications without first consulting your rheumatologist.
Let’s recap what we’ve learned today.
- Psoriatic arthritis is an inflammatory arthritis that affects about 26% of people that suffer from psoriasis and affects about 2 to 3% of the population.
- We know that there is a strong genetic link and environmental component to psoriatic arthritis, but the majority of cases happen spontaneously.
- People with nail psoriasis have a higher risk of getting psoriatic arthritis.
- The Koebner phenomenon describes the appearance of a new skin lesion in an area where healthy skin was injured. The same thing can happen in joints. This is the deep Koebner phenomenon.
- Psoriatic arthritis can present in many ways. It can cause peripheral inflammatory arthritis, axial inflammatory arthritis, enthesitis, and uveitis.
- Doctors use the CASPAR criteria to help make a diagnosis of psoriatic arthritis. You need three points to get the diagnosis because having 3 or more points has a 99% specificity and 92% sensitivity for the diagnosis of psoriatic arthritis.
- There are no specific tests help make the diagnosis of psoriatic arthritis, however, people that test positive for HLA-B*27 have a higher chance of having psoriatic arthritis in their spine.
- People with psoriatic arthritis have a higher risk of having cardiovascular disease but treatment can possibly decrease that risk.
- Psoriatic arthritis is treated with disease modifying anti-rheumatic drugs.
In part 2 of the Guide to living with psoriatic arthritis, I’ll be covering topics such as natural treatments for nail psoriasis and psoriatic arthritis, the FODMAP diet, how to exercise, and strategies on how to reduce stress. In part 3 of the Guide to living with psoriatic arthritis, I’ll be covering the financial aspect of psoriatic arthritis most notably, health insurance coverage and the prior authorization process for expensive medications.
Stay tuned and please leave your comments below!
Please follow this link to request a rheumatology consultation.
This information is offered to educate the general public. The information posted on this website does not replace professional medical advice, but for general information purposes only. There is no Doctor – Patient relationship established. We strongly advised you to speak with your medical professional if you have questions concerning your symptoms, diagnosis and treatment.
Sick woman main areas of the human body affected by psoriasis: By ann131313 via Shutterstock
Nail anatomy by Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
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