Patients with psoriasis are nearly twice as likely to have an autoimmune disease as individuals without the condition, suggest study findings.
The study found psoriasis to be strongly associated with rheumatoid arthritis in particular, and provides further evidence that it shares a common genetic or environmental cause with autoimmune diseases, say Jashin Wu (Kaiser Permanente Los Angeles Medical Center, California, USA) and co-authors.
Using data from the Kaiser Permanente Southern California database during 2004-2011, the researchers performed a retrospective cohort study of 25,341 patients aged on average 49 years with two or more diagnosis codes for any psoriatic disease. Five control individuals without the condition were matched to each psoriatic patient based on age, gender, and length of enrollment. Patients had an average 5.2 years of follow-up.
Of the enrolled patients, 10.6% had at least one code for psoriatic arthritis. Patients with psoriasis and/or psoriatic arthritis had 1.6- and 1.9-fold increased odds of at least one or two other autoimmune diseases, respectively.
Compared with the general population, these patients were at increased risk for developing 14 of the 21 studied autoimmune conditions, with the most notable associations seen with rheumatoid arthritis (odds ratio [OR]=3.6), alopecia areata (OR=2.4), celiac disease (OR=2.3), and systemic sclerosis (OR=2.1).
Other significant associations were seen with Crohn's disease (OR=1.8), Sjögren's syndrome (OR=1.7), vitiligo (OR=1.7), ulcerative colitis (OR=1.5), chronic urticaria (OR=1.5), systemic lupus erythematosus (OR=1.4), Addison's disease (OR=1.4), Giant cell arteritis (OR=1.4), pulmonary fibrosis (OR=1.3), and chronic glomerulonephritis (OR=1.2).
Analysis of associations according to gender and ethnicity revealed that female patients had a significantly higher odds for between one and three autoimmune diseases compared with male patients, at ORs of 1.3-1.6 versus 1.3-1.2 for psoriasis and ORs of 5.5-7.6 versus 4.6-3.6 for psoriatic arthritis, respectively.
The researchers caution that overascertainment or misacertainment of immune-mediated conditions may have occurred due to patients with autoimmune conditions having a greater than average number of healthcare encounters.
"Evaluating psoriasis patients for autoimmune diseases may be warranted as part of their medical care," conclude the researchers in the Journal of the American Academy of Dermatology.
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