Psoriasis - New Revelations
Psoriasis is a chronic skin disease that causes skin redness and irritation and has a significant impact on the quality of life. Psoriasis of the skin is often associated with psoriatic arthritis, characterized by joint involvement. About one quarter of patients with psoriasis also develop psoriatic arthritis. The conditions are notorious for skin, joint, and nail manifestations.
It was long believed that skin, joint, and nail manifestations shared a common cause. But recent studies suggest these to be traits of distinct disease conditions. The severity and progression of skin, joint, and nail symptoms are frequently asynchronous. For example joint disease in most patients develops up to 10 years after the initial skin presentation.
Though psoriasis and psoriatic arthritis are co-morbid conditions, the genetic mechanisms responsible for the course may be different. Even the basic physiology governing both is supposed to differ. For example, selected key immune mediators of disease in the skin and joints differ.
This explains why skin and joint symptoms frequently do not respond equally or in parallel to treatment. It is therefore best advised that the severity of skin, nails, and joints be assessed separately. Recent studies published in PLoS ONE, an open access journal were supportive of this concept.
Unfortunately a single measurement tool that has the ability to measure the presence and severity of all clinical aspects of psoriasis does not exist. A more robust analysis would hence be necessary to better investigate the skin-joint relationship.
The study results provide evidence against an association between the severity of joint and skin involvement in patients with psoriasis and psoriatic arthritis, with the possible exception of hand symptoms.
Source: Clinical Symptoms of Skin, Nails, and Joints Manifest Independently in Patients with Concomitant Psoriasis and Psoriatic Arthritis; Knut et al; PloS One 2011.