Weird, Weird, Weird, the treatment causes the disease?

How can the best biologic treatment for psoriasis and psoriatic arthritis possible cause psoriasis in rheumatoid arthritis patients? Yet TNF alpha inhibitors (Remicade, Enbrel and especially Humira) are now associated with the start of psoriasis. Something weird is going on.

The article below documents this unexpected finding. But why? Is the reason something that the TNF alpha inhibitor did or is it something else?

We know that RA, P, and PsA are similar autoimmune diseases because the exact same medications help all three.

We know that autoimmune disease runs in families. My wife's family has psoriasis, PsA, type I diabetes, and Raynaud's. My family has "stomach problems" and hives and angioedema and a possible case of RA.

We also know that when a person is diagnosed with one autoimmune disease, they are more likely than "healthy" people to be diagnosed with another. My son started with inflammatory arthritis, then psoriasis, followed by psoriatic arthritis and finally ankylosing spondylitis.

So would the RA patients have gotten psoriasis anyway because they already had the autoimmune gene or is there something about TNF alpha inhibitors that caused the onset of P?
Who knows? Stay alert for more details as they become available.

TNF-Blocker Therapy for Rheumatoid Arthritis May Trigger Psoriasis


By David Douglas

NEW YORK (Reuters Health) Feb 03 - A study by UK researchers adds to case reports of incident psoriasis occurring in rheumatoid arthritis (RA) patients treated with anti-tumor necrosis factor (TNF) alpha agents.

"We observed 25 cases of new-onset psoriasis in our cohort of almost 10,000 patients with rheumatoid arthritis receiving anti-TNF therapy," investigator Dr. Kimme L. Hyrich told Reuters Health. This compared to "no cases reported in our non-biologic treated control cohort."
As reported in the February issue of the Annals of the Rheumatic Diseases, Dr. Hyrich of the University of Manchester and colleagues studied data on 9826 anti-TNF-treated patients and 2880 treated with DMARDS (disease modifying anti-rheumatic drugs). Based on the 25 psoriasis cases, the investigators calculate that the incidence rate for new-onset psoriasis was 1.04 per 1000 person years in the TNF-blocker cohort.

The incidence was significantly higher in patients treated with adalimumab than in those who received etanercept or infliximab.

"These findings present an interesting paradox," Dr. Hyrich pointed out, "as anti-TNF therapies are very effective in the treatment of severe psoriasis and psoriatic arthritis. The explanation behind these reported cases remains largely unknown."

"Further observation to understand their etiology is required," she concluded, "before any definite conclusions regarding the association between anti-TNF therapies and psoriasis can be made or guidelines for specific treatment of the condition issued."
Ann Rheum Dis 2009;68:209-215.