NEW YORK (Reuters Health) - A number of environmental exposures, including trauma, are associated with the onset of inflammatory arthritis in patients with psoriasis, findings published in the Annals of the Rheumatic Diseases indicate.

"Psoriatic arthritis can be considered as a 'disease within a disease'," Dr. Ian N. Bruce, of the University of Manchester, UK, and colleagues write. Psoriatic arthritis is "inflammatory arthritis on a background of pre-existing or future development of psoriasis."

"Usually arthritis post-dates, often by several years, the onset of psoriasis," they note. So for patients with psoriasis, it is would be helpful to know what factors increase their risk of developing this condition.

To investigate, the researchers compared 98 patients who developed inflammatory arthritis within the past five years to a "control group" of 163 patients with psoriasis but not arthritis. A postal questionnaire was used to assess potential factors associated with the development of inflammatory arthritis.

Exposures before the onset of arthritis that positively correlated with the condition included rubella vaccination (4.6 percent for psoriatic arthritis patients vs 0.7 percent for controls); trauma requiring medical care (14.9 percent vs 7.9 percent); and recurrent oral ulcers (25.3 percent vs 8.9 percent).