Psoriatic Arthritis: How to Identify and Treat it?

The classic description of the clinical characteristics of rheumatism psoriasis was published in 1973. However,it was only in 1983 that skeletal remains unearthed from a Byzantine monastery in the Judean desert, dating from the fifth century AD, allowed for the observation of visual and radiographic images consistent with a psoriatic bone and joint disease.

Psoriatic arthritis is a chronic inflammatory rheumatism (CIR), which is part of the spondyloarthritis group. It should not be confused with osteoarthritis , which is a joint disease. It occurs due to the immune system's reaction against ligaments, tendons, and joints. It is estimated that 30% of patients suffering from this disease also have another form of psoriasis.

There are three types of psoriatic arthritis distinguished:

• The axial form: affects the spinal column, the joints of the thorax as well as those that connect the pelvis and the lumbar vertebrae;

• The peripheral joint form : affects the knees, hips, shoulders, fingers or toes. This is the most common form;

• The form that affects the heels and elbows.

It is possible that some patients suffering from psoriatic arthritis may be affected by one or more of these forms at the same time.

Sometimes, no known cause triggers this disease, yet there are still factors that promote its onset. These can include an infection, medication intake, psychological or physical stress, or even trauma in certain cases. Genome-wide analyses have shown that genetic factors promote the onset of this form of psoriasis. Certain polymorphisms in the gene encoding the interleukin-23 receptor (IL23R), as well as variants in the expression of the nuclear factor κB (NF-κB) gene and the expression of TNF are associated with psoriatic arthritis. Further studies still need to be conducted to understand these genetic factors in more detail.

Recent studies have also highlighted the significance of the interleukin-23–interleukin-17 and TNF pathways in the pathogenesis of psoriatic arthritis. The expression of interferon-α by plasmacytoid dendritic cells activates dermal dendritic cells, which trigger the differentiation of type 1 helper T cells (Th1) and Th17 cells. These lymphocytes return to the dermis and are the source of a complex inflammatory response.

The CASPAR Criteria (Classification Criteria for Psoriatic Arthritis) are classification criteria for psoriatic arthritis that were defined in 2006 and allow for a diagnosis to be established.

To detect psoriatic arthritis, one must be vigilant about the presence of skin psoriasis as well as painful joint swelling that can awaken you at night. The most common characteristic symptoms are inflammatory joint pains that occur at night or in the morning. Rest does not alleviate these pains, unlike in cases of mechanical wear such as osteoarthritis. The severe and disabling forms of this disease only affect 10 to 20% of patients.

The aim of psoriatic arthritis treatments is primarily to alleviate pain and inflammation. They help combat any potential stiffness if it's a case of axial form of psoriatic arthritis. This type of treatment mainly utilises analgesics and non-steroidal anti-inflammatory drugs.

For patients experiencing more severe symptoms, it is possible to consider disease-modifying antirheumatic drugs (DMARDs). These are a class of drugs indicated for the treatment of several inflammatory arthritides, as well as for the management of other connective tissue diseases. Unfortunately, the number of clinical trials is still too limited to guarantee their effectiveness.

Treatments based on interleukin-17 inhibitors, an inflammatory cytokine, such as ixekizumab have shown efficacy in a phase 3 clinical trial in patients with psoriatic arthritis. Anti-TNF alpha agents have also proven to be effective in combating this form of psoriasis. This key cytokine acts as an essential modulator of the inflammatory response. In the course of chronic inflammatory rheumatism, TNF-alpha is present in excessively high quantities in the blood, and in the joints.

As for the axial forms of psoriatic arthritis, they require rehabilitation sessions. The aim is to alleviate the symptoms while enabling the patient to become aware of the bad habits to be eliminated.

SAURAT J. & al. Psoriasis. Dermatologie et infections sexuellement transmissibles (2016).

RITCHLIN C. T. & al. Psoriatic Arthritis. The new england journal of medicine (2017).