Psoriasis can, in 10 to 30% of cases, associate with joint damage. It is then a chronic inflammatory rheumatism. We talk about psoriatic arthritis.
Psoriatic arthritis can start in an acute mode or settle insidiously over several years.
Different clinical presentations are possible:
- A mono articular (that is to say affecting only one articulation) or articular oligo (at most 3 articulations) in 70% of the cases. The knee is often affected with possibility of effusion sometimes important and very inflammatory.
- Polyarticular involvement, which mimics rheumatoid arthritis. Unlike rheumatoid arthritis, immunological examinations remain negative throughout the evolution.
- Some attacks are very suggestive of psoriatic arthritis : the dactylitis, inflammation which affects the whole of a must or a toe giving a "sausage" appearance, the achievement of the last phalanges contrary to rheumatoid arthritis, the pains of entheses for example Achilles tendon.
- Impairment of the spine may be associated, especially if the HLA B27 gene is present.
The age of onset is more often between 40 and 50 years old but an early or late start is possible.The majority of psoriatic arthritis is accompanied by skin psoriasis that precedes joint damage. But in 15% of cases, the cutaneous and articular involvement is simultaneous, and in 15 to 25%, cutaneous involvement occurs after the articular lesions, sometimes very long after. A family history of psoriasis is also a guiding element.
Still's disease or juvenile arthritis
Still's disease is juvenile idiopathic arthritis (JIA). It is estimated that in France around 5, 000 children under the age of 16 have JIA. What are the symptoms and how to treat it?
The diagnosis of psoriatic arthritis is not always easy to perform at the clinical examination by the doctor. It can be assisted by biological tests by taking blood (sedimentation rate, or CRP can be increased).
The immunological examinations (rheumatoid factors, anti-citrulline antibodies) are negative which pleads against rheumatoid arthritis.
If it is possible, the articular puncture finds a highly inflammatory liquid without crystals which excludes a drop or a chondrocalcinosis.
Radiographs may show a fairly typical appearance, with the association of destructive and constructive lesions, but it is important to make the diagnosis early, before the occurrence of joint destruction.
Careful research of psoriasis lesion including on the nails or in the scalp is very important.
It is important to think about it in case of suspicious articular pains and then to quickly consult. Early treatment may prevent progression of the disease. Untreated joint psoriasis can lead to destruction or deformity of the joints.
The treatment of psoriatic arthritis should be aimed at remission or minimal activity of the disease. In forms that may be active, or affecting less than three joints, NSAIDs or infiltrations may be sufficient to control the disease.
In case of more severe injury, a background treatment is then proposed. The efficacy of these treatments was much less well evaluated than in rheumatoid arthritis. Sulfasalazine, ciclosporin and leflunomide have been validated. Their effectiveness is however moderate and especially they do not act on the pain of the entheses. European recommendations put methotrexate first, although the level of evidence is low. In practice it is a treatment often used at doses of 15 to 25 mg per week. There is no evidence of efficacy in preventing radiographic lesions with methotrexate. It is recommended in the active forms (at least one painful joint and at least one swollen joint) or when NSAIDs and infiltrations do not control the disease after 3 months, or immediately when the damage affects more than 5 joints, that there is a dactylitis, a radiographic attack, a sanguineous inflammation. In case of failure or intolerance of methotrexate, second-line therapy is recommended for sulfasalazine or leflunomide.
In the second line, several biological treatments have proven their effectiveness . All anti-TNF alpha are effective on all manifestations of psoriatic arthritis including cutaneous, with significant effectiveness. In the trials, the combination with methotrexate does not seem to increase the efficacy of TNF antagonists, contrary to what is observed in rheumatoid arthritis.
New biotherapies targeting the Il23 / Th17 pathway have recently been marketed : Ustekinumab (Stelara) and Secukinumab (Cosentyx). These two molecules are used subcutaneously alone or in combination with methotrexate. The 6-month clinical response appears to be lower than that seen with TNF alpha antagonists but is similar to one year suggesting a more gradual effect. These two molecules are also effective on the skin. European recommendations advocate second-line use in the event of failure or intolerance to an anti-TNF, but the US recommendations place them on the same level.
Finally, apremilast (Otezla) is a small molecule inhibiting PDE4 with an oral intake . Although its clinical efficacy in psoriasis is well demonstrated, the efficacy on joint damage is lower than biotherapies. It is therefore recommended in case of contraindication to these treatments.You want to react, to give your testimony or to ask a question? See you in our FORUMS Diseases and skin care!
Read also :
> C-reactive protein (CRP): what is it?
> Learn more about rheumatoid arthritis
> Fingers affected by rheumatoid arthritis
Author: Dr Agnès Chabot, May 2017