Objective: To identify potential risk factors for the onset of inflammatory arthritis (IA) in a large cohort of patients with psoriatic arthritis (PsA) of recent onset.
Methods: We recruited cases with psoriasis and an onset of IA within the past 5 years. Controls were patients who had psoriasis but no arthritis. We assessed potential factors associated with the development of IA using a detailed postal questionnaire. An unmatched analysis adjusted for age and gender was performed. Exposure was censored in the controls at a "dummy-date" assigned randomly in proportion to the percentage of cases developing IA in any given year.
Results: We studied 98 cases and 163 controls. Exposures showing a positive association prior to the onset of IA in patients with psoriasis were: rubella vaccination (OR [95% C.I.] = 12.4 [1.2-122]), injury sufficient to require a medical consultation (2.53 [1.1-6.0]), recurrent oral ulcers (4.2 [2.0-9.0]) and moving house (2.3 [1.2-4.4]). Cases were also more likely to have experienced a fractured bone requiring hospital admission (50% vs. 9%, p=0.040).
Conclusions: We found a number of environmental exposures associated with the onset of IA in subjects with psoriasis. The strongest associations were with trauma thereby adding to the hypothesis of a ‘deep Koebner phenomenon’ in PsA. Our data also suggest that exposure of the immune system to certain infection related triggers may also be of relevance. Further studies are needed to verify these observations and to examine potential immunological mechanisms that underlie them.
- case control study
- psoriatic arthritis
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