What is Psoriatic Arthritis?
Psoriatic arthritis is a long-term condition where the joints become swollen and painful. This is linked to psoriasis, a skin condition, and it affects around 20% of individuals who have psoriasis. This form of arthritis shares several similarities with other types of arthritis, specifically, ankylosing spondylitis and rheumatoid arthritis.
Usually, there’s no presence of certain proteins (referred to as “seronegative”) that are typically associated with other types of arthritis. However, some patients might test positive for these proteins, specifically, the rheumatoid factor and anti-cyclic citrullinated peptide antibodies.
The symptoms of psoriatic arthritis can vary from person to person and can change over time. Sometimes, it can shift from one pattern of symptoms to another. Psoriatic arthritis can cause significant financial and emotional problems. However, recent advancements in medical science have led to a deeper understanding of the disease, which has resulted in the development of new treatments.
What Causes Psoriatic Arthritis?
Psoriatic arthritis, a type of arthritis that often occurs with a skin condition known as psoriasis, is caused by a range of different factors. These include a combination of your genes and elements in your environment, which result in an irregular immune response that causes inflammation in the skin, joints, and sometimes other organs.
Genetic factors play a big part in psoriatic arthritis. In fact, around a third to a half of people with the condition have a close relative who also has psoriatic arthritis or psoriasis. Many different genes are involved, with some responsible for the immune system recognizing harmful substances, and others involved in triggering immune responses and inflammation.
Interesting to note is that the genetic links between psoriatic arthritis and psoriasis are not exactly the same; some of the genes linked to psoriatic arthritis aren’t linked to psoriasis and vice versa. Even within psoriatic arthritis, different genes are associated with different types of the disease.
For example, several genes from the HLA group are associated with psoriatic arthritis. These include HLA-B*08:01, HLA-B*27:05, and HLA-C*06:02. Each of these genes is associated with various symptoms and features of the disease. For instance, the HLA-B*08:01 gene is associated with arthritis affecting the peripheral joints (joints not in the core of the body), joint damage, and ankylosis (stiffening of a joint). The HLA-B*27:05 gene is associated with arthritis that generally affects the spine and the lower back, as well as swelling at the where tendons and ligaments meet the bone.
Some genes, one example being IL-23R, are responsible for protein production that causes inflammation. Psoriasis, on the other hand, is more closely associated with the HLA-B*57:01 and HLA-C*06:02 genes than psoriatic arthritis is.
Environments also play a role in psoriatic arthritis, though the specifics can be hard to pin down. Some scientists think that there might be a link between the condition and streptococcal infection or antibiotic exposure. In some cases, physical injuries to the skin and joints might trigger the onset of skin or joint symptoms. Finally, while smoking can make rheumatoid arthritis more likely in people with certain genes, it seems to guard against the development of psoriatic arthritis.
Risk Factors and Frequency for Psoriatic Arthritis
Psoriatic arthritis is a condition that varies widely among different population groups. Generally, the prevalence of this disease is between 0.05% to 0.25%. However, among patients who already suffer from psoriasis, a skin condition, the prevalence rises to between 6% and 41%. What’s more, due to underdiagnosis, up to 15.5% of people with psoriatic arthritis may be unaware they have it.
The disease typically presents in patients in their 30s and 40s and affects both genders equally. It’s interesting to note that in most patients (68%), skin symptoms appear before arthritis. In 15% of cases, arthritis and skin disease start at the same time, and in 17%, arthritis shows up before any skin issues, making diagnosis difficult.
- For psoriatic arthritis, certain risk factors include severe psoriasis type, scalp, intergluteal, and perianal psoriasis, nail pitting, low education level, and uveitis.
- Its annual incidence is 1.9 to 2.7% per 100 psoriatic arthritis patients.
- At 5 years, 1.7% of psoriasis patients have psoriatic arthritis; at 10 years, 3.1%; at 20 years, 5.1%, and at 30 years, 20.5%.
When considering worldwide statistics, the presence of psoriatic arthritis ranges from 0.1% to 1%. This rate can differ greatly due to geographic and ethnic variations
- In Europe, the prevalence is 0.19%, with figures in Norway and Sweden at 0.67% and 0.02% respectively.
- In North America, it is 0.13%.
- The Middle East report 0.01% prevalence, South Asia 0.06%, South East Asia 0.05%, and East Asia 0.17%; with China at 0.002%, Taiwan at 0.004%, and Japan at 0.001%.
- South America has a 0.07% prevalence rate.
- The prevalence has been increasing over time.
Among patients with psoriasis, 19.7% have psoriatic arthritis, with more adults (21.6%) affected than children (3.3%). Also, the disease is more associated with severe psoriasis (24.6%) than mild psoriasis (15.8%). It is noted that the proportion of psoriasis patients with psoriatic arthritis varies depending on location and ethnicity: Europe (22.7%), North America (19.5%), South America (21.5%), Africa (15.5%), and Asia (14%).
Signs and Symptoms of Psoriatic Arthritis
Psoriatic arthritis is a condition that comes in many forms. Doctors use five categories to describe the different types of psoriatic arthritis. The asymmetrical type, the most common one, usually affects fewer than five of your joints. The symmetrical type is similar to rheumatoid arthritis and often affects the same joints on both sides of your body. Distal psoriatic arthritis is notable because of the way it favors the joints closest to the nails. Severe destructive joint disease is called arthritis mutilans, which involves joint damage and deformities. Spondyloarthritis patterns occur when the spine or pelvis is affected, either alone or along with other joints.
- Asymmetrical psoriatic arthritis impacts fewer than five joints and it’s different on each side of your body.
- Symmetrical psoriatic arthritis is like rheumatoid arthritis and affects matching joints on both sides of your body.
- Distal psoriatic arthritis specifically targets the joints near your nails in your fingers and toes.
- Arthritis mutilans can cause severe joint damage and deformities, especially in your hands and feet.
- Spondyloarthritis patterns involve your spine or pelvis, with or without other affected joints.
The patterns of psoriatic arthritis can change over time. For instance, people who start with asymmetrical arthritis often develop symmetrical arthritis as the disease progresses.
Doctors examine each case of psoriatic arthritis in terms of joint and non-joint symptoms. Joint symptoms involve those of inflammation, growth, or abnormal form. Non-joint symptoms can include the type and seriousness of skin disease, nail issues, and eye problems like uveitis.
- Involvement of fewer joints (oligoarticular) or many joints (polyarticular)
- Inflammation near where ligaments and tendons attach to bones (enthesitis)
- Swelling of entire fingers or toes (dactylitis)
- Inflammation of the spine or pelvic joints (sacroiliitis and spondylitis)
- Psoriasis skin disease
- Nail disease including nail separation, pitting, and bleeding under the nail
- Eyelid inflammation (uveitis), which is different from that associated with spinal arthritis
The severity of the skin, nail, and joint problems doesn’t always match up in patients with psoriatic arthritis.
Testing for Psoriatic Arthritis
If you are being tested for psoriatic arthritis, a type of arthritis that can occur in people with the skin condition psoriasis, your doctor might suggest various tests. These include blood tests that look for specific markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which often rise during inflammation in the body. Yet, even if these markers aren’t high, this doesn’t necessarily mean you don’t have psoriatic arthritis. In fact, only around 40% of patients with this condition show increased levels of these markers.
Your doctor might also look for antibodies, which are proteins made by our immune system that mistakenly attack normal cells. In particular, they might look for rheumatoid factor and anti-cyclic citrullinated peptide antibodies. These aren’t traditionally found in people with psoriatic arthritis, so if the rheumatoid factor is negative, it may support the diagnosis. However, some studies have shown that a small percentage of people with psoriatic arthritis may have these antibodies. Certain other antibodies, antinuclear antibodies, might also be detectable but usually at low levels.
Besides blood tests, your doctor might want to conduct imaging tests if they suspect you have psoriatic arthritis. These tests, like x-rays, CT scans, ultrasounds, or MRI, can reveal specific signs or ‘patterns’ in the joints that are common in this condition. For instance, these can include ‘pencil-in-cup’ deformity, bone destruction, joint space narrowing, and new bone formation at the same place.
A concerning aspect is that psoriatic arthritis can lead to permanent damage in joints, visible on x-rays, in almost half of patients within the first 2 years of the disease. Therefore, early detection and treatment are imperative. Advanced imaging techniques like musculoskeletal ultrasound and MRI can show early joint inflammation and damage, as well as changes in the lower spine. These techniques are generally more sensitive but aren’t necessarily required for diagnosing psoriatic arthritis.
Finally, doctors refer to classification criteria for diagnosing psoriatic arthritis. The most accepted of these is the CASPAR criteria, which includes factors like skin psoriasis, nail lesions, inflammation in fingers or toes (dactylitis), negative rheumatoid factor, and new bone formation near joints. Scoring at least 3 points on the criteria can indicate psoriatic arthritis with high specificity and sensitivity.
Treatment Options for Psoriatic Arthritis
Treating psoriatic arthritis involves tailoring the treatment to the severity of the disease, the amount of joint damage, the extent of the disease outside of the joints, patient’s personal preference, and other health conditions. Incorporating non-drug therapies such as physical therapy, occupational therapy, exercise programs, and quitting smoking into the treatment plan is highly recommended.
A treatment strategy that aims to control the disease activity and minimize joint damage is considered the most effective. Depending on the extent and duration of the disease, targets for low disease activity or remission should be set.
The treatment for psoriatic arthritis could differ depending on the affected areas such as peripheral joints, enthesitis (inflammation of where tendons or ligaments attach to the bone), dactylitis (inflammation of an entire finger or toe), axial disease (inflammation of the spine and/or pelvis), and skin or nail disease. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used for mild peripheral joint symptoms. For mild to moderate peripheral arthritis, conventional synthetic disease-modifying antirheumatic drugs (DMARDs) may be used. Severe peripheral arthritis usually requires treatment with a specific type of DMARDs called biologic DMARDs.
Axial disease and enthesitis usually require a similar treatment approach. Patients who do not respond to NSAIDs should transition to biologic DMARDs. Different types of biologic DMARDs may be recommended over others, depending on the nature and severity of the disease. For example, some may be more effective for severe psoriasis, a common skin condition in psoriatic arthritis. Others may be preferred if the patient prefers oral medication.
The American College of Rheumatology (ACR) and National Psoriasis Foundation (NPF) guidelines recommend using biologic DMARDs as the first line of treatment for patients with psoriatic arthritis. They provide specific recommendations for treating active psoriatic arthritis, which is defined as, causing symptoms at a level that is bothersome to the patient due to one or more of the following: swollen joints, tender joints, inflammation of an entire toe or finger, inflammation of the places where tendons attach to bones, axial arthritis, active skin and/or nail involvement, and inflammation outside of the joints such as uveitis (eye inflammation) or inflammatory bowel disease.
The European League Against Rheumatism (EULAR) also provides similar recommendations for managing psoriatic arthritis. They emphasize that the disease treatment should aim for the best care and must be based on a shared decision between the patient and rheumatologist. They also underscore the importance of considering non-musculoskeletal manifestations (for example, affecting the skin, eye, and gastrointestinal tract) and comorbidities (other health conditions) such as metabolic syndrome, cardiovascular disease, and depression.
In summary, managing psoriatic arthritis involves a combination of non-drug and drug treatments, incorporating patient’s preference, and adapting to the unique presentation of the disease in each individual.
What else can Psoriatic Arthritis be?
Psoriatic arthritis, a type of inflammatory arthritis, can be difficult to diagnose because it shares signs and symptoms with other conditions such as rheumatoid arthritis, reactive arthritis, and ankylosing spondylosis. Here’s how these diseases differ:
- Rheumatoid arthritis typically affects the same joints on both sides of the body (it’s symmetrical). It also generally does not affect the joints closest to the fingernails and toenails (known as the distal interphalangeal joints), unlike psoriatic arthritis.
- On the other hand, ankylosing spondylosis usually starts earlier in life than psoriatic arthritis. Moreover, it usually affects the joints in the lower back where the spine joins the pelvis (the sacroiliac joints) symmetrically, whereas in psoriatic arthritis, this involvement is usually asymmetrical.
What to expect with Psoriatic Arthritis
Psoriatic arthritis is a form of arthritis that can cause severe health issues and greatly affect a patient’s quality of life. There are several features that can suggest a person may have a more severe form of the disease and a poor prognosis. These include having a large number of joints that are actively inflamed known as polyarticular presentation, an increased level of a blood test known as the erythrocyte sedimentation rate, observable or detectable damage in clinical tests or X-rays, loss of function, and a decreased quality of life.
Possible Complications When Diagnosed with Psoriatic Arthritis
Psoriatic arthritis, which was once thought to be mild, is now recognized as a severe disease that needs specifically targeted treatment and frequent check-ups. While it’s possible to eliminate the symptoms entirely, many patients will continue to experience persistent inflammation related to the disease.
People with a related condition called uveitis, where the middle layer of the eye becomes inflamed, will need to be assessed and treated by an eye doctor or ophthalmologist. Additionally, patients with psoriatic arthritis are more likely to have several other health conditions at the same time, including, but not limited to:
- Metabolic syndrome, a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes
- Obesity
- Diabetes mellitus, a type of diabetes that leads to high blood sugar levels
- Hyperlipidemia, a condition where there are high levels of fats in the blood
- Hypertension, also known as high blood pressure
- Cardiovascular disease, a range of conditions affecting the heart and blood vessels
Preventing Psoriatic Arthritis
Patients living with psoriatic arthritis should be thoroughly informed and advised about how long-term and variable this condition can be. Key aspects include the importance of both medication and lifestyle changes. Making healthy lifestyle choices, such as regular exercise, quitting smoking, losing weight, and attending physical and occupational therapy sessions can greatly help in managing the symptoms.
It’s important to remember that psoriatic arthritis can fluctuate, meaning it may get better or worse over time. Therefore, constant check-ups and supervision from a team of various health professionals is necessary.
Patients should also be made aware of the potential side effects of certain medications that suppress the immune system, which are often used to treat this condition. It’s also beneficial for the patient’s family to be informed about the condition and treatment as they can provide important support.