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Friday 23 August 2019
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Expert view: Beyond TNF-alpha - differentiating PsA and RA

Psoriatic disease is a chronic inflammatory systemic condition characterised by psoriasis, which affects up to 3% of the general population, and in about 30% of cases, by psoriatic arthritis (PsA), which may also be diagnosed in the absence of a personal history of psoriasis.
 
From a clinical and immunological standpoint, psoriasis and PsA represent a continuum within a prototype for chronic inflammation, but largely different from rheumatoid arthritis (RA), although both lead to reduced quality of life and elevated risk of malignancy, cardiovascular disease, and depression. Patients with psoriatic disease often manifest other chronic inflammatory comorbidities and associated conditions, well represented by inflammatory bowel disease and uveitis. 
 
In contrast to RA, no serum autoantibody is associated with PsA, whereas other biomarkers have been proposed for early diagnosis of the disease or to predict treatment response for a more adequate resource allocation. From a clinical standpoint, the manifestations of PsA are widely variable and only partially overlap with RA; particularly as only PsA affects the spine, thus being defined as spondyloarthritis. Despite numerous improvements in the management of PsA, there remain numerous unmet needs. 
 
First and foremost, there is a significant unmet need for reliable tools for the early diagnosis of PsA in psoriasis. Our current understanding of the probability of developing PsA in psoriasis or to achieve an early diagnosis could be defined as primitive, with limited agreement on the clinical manifestations to be sought. Despite the presence of an obvious risk factor for PsA in the skin manifestation, the individual clinical judgment and medical history remain the sole driver of PsA screening, which differs from RA with serum autoantibodies specific for the disease and pre-dating overt clinical manifestations. 
 
Predicting an effective and safe medication to manage the disease is another significant challenge, and currently approximately 40% achieve meaningful responses such as minimal disease activity status with second- or third-line treatments. These two unmet needs result in the major unmet need, that is, the necessity for early treatment that will minimise the risk of disease progression along with the costs and with an optimal safety profile. One putative solution for this moves from a multidisciplinary approach, which includes foremost dermatology and rheumatology specialists, and this is certainly also a goal in RA.