July 29, 2021

Psoriatic arthritis: causes, symptoms, risk factors and treatment

what causes psoriatic arthritis

Psoriatic arthritis (PSA) is a chronic inflammatory disease that causes pain, swelling and stiffness in the joints. Although it is more common in people with psoriasis, 20% of people with Psoriatic arthritis do not have this skin disease. Evolving in flare-ups, sometimes separated by long periods of lull, PSA sometimes goes unnoticed, or is mistaken for another form of chronic rheumatism such as spondylitis. Treatments make it possible to relieve acute attacks, but also to reduce their frequency of occurrence, and therefore their deleterious course.

What is psoriatic arthritis?

Psoriatic arthritis is a chronic inflammatory arthritis that is part of a group of inflammatory diseases called spondyloarthritis, which includes ankylosing spondylitis, reactive arthritis, and arthritis associated with chronic inflammatory bowel disease (IBD: Crohn’s disease and ulcerative colitis). It results in inflammation of the joints causing pain and stiffness, associated with fatigue and is caused by an immune system reaction against the joints, tendons and ligaments.

There are three forms of psoriatic arthritis:

  • the so-called “axial” form, which affects the spine, the thorax joints and those which join the pelvis and the lumbar vertebrae (sacroiliac joints); this form can sometimes be confused with axial spondyloarthritis.
  • the so-called “peripheral articular” form, which affects the knees, hips, shoulders, fingers or toes; this is the most common form.
  • the so-called “enthesitis” form, which affects the heels and elbows. Entheses are the attachments of tendons and ligaments to bones.

A patient with psoriatic arthritis may have one or more of these forms, simultaneously or in succession.

Who is affected?

Psoriatic arthritis affects as many men as it does women. Symptoms usually appear in people between the ages of 30 and 50. About 80% of people who suffer from psoriatic arthritis are also affected by psoriasis. And nearly 30% of people with psoriasis will develop psoriatic arthritis. Usually, the rheumatic form appears 5 to 10 years after the onset of the skin symptoms of psoriasis, but in 15% of patients with psoriasis it appeared before the skin symptoms.

What causes psoriatic arthritis?

Like psoriasis and other chronic inflammatory arthritis, psoriatic arthritis is caused by a combination of genetic predisposition and contributing environmental factors (eg stress, physical or emotional trauma, or infections). The immune system reacts abnormally and attacks the tissues in the joints as if they were foreign bodies. This autoimmune reaction causes local inflammation that causes pain, stiffness and swelling in the joints and, in the longer term, damage.

What are the risk factors of psoriatic arthritis?

  • Genetic factors: people carrying the HLA B27 gene have a higher risk of developing the disease: this gene is present in 25% of people with psoriatic arthritis. HLA B27 codes for a cell surface protein that is involved in their recognition by the immune system, it is these HLA proteins that allow the immune system to differentiate between the body’s own cells and foreign ones. When HLA B 27 is present, the body sometimes mistakes its own cells for foreign cells that it fights off with inflammation.
  • Non-genetic factors: other risk factors for psoriatic arthritis are suspected: obesity, type 2 diabetes, high blood pressure, metabolic syndrome and, of course, psoriasis, especially in its severe forms.

What are the symptoms of psoriatic arthritis?

The symptoms of psoriatic arthritis are nonspecific and closely resemble those of other forms of chronic inflammatory rheumatism. When the acute attacks (flare-ups) are mild and widely spaced (several years between flare-ups), it is not uncommon for psoriatic arthritis to go unnoticed. It is estimated that in half of patients with psoriasis and psoriatic arthritis, the latter has never been diagnosed.

Two symptoms are present in 30 to 50% of patients, and are particularly characteristic:

  • Enthesitis, or inflammation of the entheses, the attachments of ligaments and tendons on the bones, causing joint pain;
  • Dactylitis, an inflammation of the joints of the fingers which causes pain and swelling: the finger takes a “sausage” shape.

These symptoms are often asymmetric (only one side of the body is affected).

Other symptoms can also be observed:

  • Joint pains that wake the patient up in the middle of the night
  • Fatigue, especially during flare-ups
  • A morning joint stiffness which is relieved by movement
  • Swelling in the joints due to inflammation of the membrane that protects the joints (the “synovial membrane”). These swellings are evidence of “synovial effusion,” which is an increase in the volume of fluid in the joint.

In people who suffer from psoriasis, a symptom is frequently present in cases of psoriatic arthritis (70 to 80% of cases): pitting (small craters appear on the nails). In some cases, it may be accompanied by inflammation of the eyes (uveitis), chronic inflammatory bowel disease (IBD: Crohn’s disease or ulcerative colitis), cardiac arrhythmias, or heart valve abnormalities.

How does psoriatic arthritis progress?

Psoriatic arthritis progresses in acute attacks (“flares”) separated by periods of lull (remission). In people who also have psoriasis, the Psoriatic arthritis flare-ups are independent of the psoriasis flare-ups.

Left untreated, psoriatic arthritis can cause irreversible joint stiffness (this is called ankylosis), or even irreversible joint deformities. These complications can cause disability.

What are the treatments psoriatic arthritis?

Treatment is based on the prescription of drugs, but also on orthopedic devices, functional rehabilitation, adapted physical activity and, possibly, surgical interventions.

Medicines prescribed for psoriatic arthritis aim to relieve pain and prevent joint damage by reducing local inflammation. They also help to limit the loss of joint mobility.

DMARDs (Disease-modifying antirheumatic drugs) are prescribed to prevent psoriatic arthritis flare-ups in people who have them frequently, or when treatments to relieve the flare-ups are not enough. These treatments aim to partially inhibit the action of the immune system to reduce inflammation: they are called “immunosuppressive”. These treatments are reserved for severe or moderate psoriatic arthritis, which have a strong impact on the patient’s quality of life.

Psoriatic arthritis flare-ups are usually relieved by taking nonsteroidal anti-inflammatory drugs (NSAIDs, e.g., ibuprofen or ketoprofen). In some cases, analgesics (pain medications) may be prescribed for a limited period of time. Finally, it is possible to inject corticosteroids (drugs from the cortisone family) directly into the painful joint(s) for relief.

Besides drugs, other types of treatment are available to relieve the symptoms of psoriatic arthritis:

  • The wearing of orthotics, designed to limit movement of the affected joints, can relieve pain, and prevent or limit joint deformities.
  • Functional rehabilitation, implemented by a physiotherapist who carries out programs adapted to the affected joints. The sessions, performed alone or in groups, aim to preserve joint mobility and muscle strength, and to relieve pain.
  • Surgical interventions, performed in exceptional cases where the joints are severely damaged.