The heart of the article goes on to discuss Kazanis' research, which demonstrates that different diseases co-occur with psoriasis vs. psoriatic arthritis. The article also highlights some of the measurement issues in this study. It's worth a read...
Support for the one-disease concept comes from the observation that arthritis occurs more frequently in patients with cutaneous psoriasis than in nonpsoriatic controls.On the other hand, the fact that a drug such as cydosporine is effective for the skin manifestations of psoriasis but provides little benefit for psoriatic joint symptoms has caused many physicians to lean toward the view that psoriasis and psoriatic arthritis are two diseases, albeit possibly sharing some immunopathogenetic elements, Ms. Kazanis said.
My two cents? I'm again struck with the similarities between psoriatic arthritis and rheumatoid arthritis, both in symptoms and the types of treatment that work. We really are just beginning to learn about these diseases, and anything is possible. What if psoriatic arthritis and rheumatoid arthritis are the same disease, with a few different symptoms? What if rheumatoid factor is just a symptom that some folks develop? And... what if psoriasis is a different disease that occurs a lot in people with PsA/RA type arthritis? What do you think?
I really gotta go get my M.D. This armchair speculation is making me woozy.