Psoriasis Linked to Autoimmune Diseases

Janis C. Kelly

October 22, 2012

Patients with psoriasis are more than 50% more likely than patients without psoriasis to have at least 1 other autoimmune disease and are nearly twice as likely to have at least 2 other autoimmune diseases, Jashin J. Wu, MD, director of dermatology research and associate residency program director in the Department of Dermatology at Kaiser Permanente Los Angeles Medical Center, California, and colleagues report in an article published online June 4 and in the November print issue of the Journal of the American Academy of Dermatology.

Dr. Wu told Medscape Medical News, "Psoriasis patients were more likely also to have other autoimmune diseases, and that the strongest association was with rheumatoid arthritis [RA]."

Dr. Wu and colleagues conducted a retrospective cohort study among 25,341 Kaiser patients, each of whom had 2 or more diagnosis codes for a psoriatic disease and was treated between January 2004 and February 2011. Each was matched with 5 Kaiser members without this case definition but with similar age, sex, and length of plan enrollment. The analysis included Crohn's disease, ulcerative colitis, type 1 diabetes mellitus, alopecia areata, hemolytic anemia, giant cell arteritis, multiple sclerosis, systemic lupus erythematosus, vitiligo, Graves disease, Hashimoto disease, chronic glomerulonephritis, pulmonary fibrosis, Sjogren syndrome, Addison disease, immune thrombocytopenia, chronic urticaria, celiac disease, and primary biliary cirrhosis.

"Patients with psoriasis were more likely to have at least 1 other autoimmune disease (odds ratio [OR] 1.6; 95% confidence interval [CI] 1.5-1.7) and to have at least 2 other autoimmune diseases (1.9; 95% CI 1.6-2.4)," write the authors. "Psoriasis was positively associated with 17 of the 21 studied autoimmune diseases, with 14 of these associations being statistically significant. The strongest association was with rheumatoid arthritis (3.6; 95% CI 3.4-3.9; [P < .0001])."

The authors also found that psoriasis doubled the risk for alopecia areata, celiac disease, and systemic sclerosis and that patents with psoriatic arthritis had higher risk for most autoimmune diseases than those with psoriasis alone. In fact, note the researchers, patients included in the study with psoriatic arthritis had a higher odds ratio for development of any of the autoimmune diseases evaluated except alopecia areata, primary biliary cirrhosis, chronic urticaria, and vitiligo compared with patients with psoriasis alone.

Compared with the general population, patients with psoriatic arthritis were more likely to have an autoimmune diagnosis, most notably RA (odds ratio [OR], 33.0; 95% confidence interval [CI], 27.1 - 40.3), systemic lupus erythematosus (OR, 3.1; 95% CI, 1.9 - 4.9), Sjogren syndrome (OR, 5.3; 95% CI, 3.3 - 8.7), systemic sclerosis (OR, 2.9; 95% CI, 1.4 - 6.4), celiac disease (OR, 2.9; 95% CI, 1.2 - 7.4), giant cell arteritis (OR, 2.9; 95% CI, 1.5 - 5.5), or hemolytic anemia (OR, 2.7; 95% CI, 1.4 - 5.2).

Dr. Wu said, "Clinicians should be aware of these increased risks, as the treatment for psoriasis may affect the autoimmune disease in a different way. Or if there is a patient with psoriasis and an autoimmune disease, then perhaps one treatment can be selected to treat both psoriasis and that autoimmune disease."

Mark G. Lebwohl, MD, professor and chair of the Department of Dermatology at Mount Sinai School of Medicine, New York City, reviewed the study for Medscape Medical News. Dr. Lebwohl said that this analysis adds to other recognized associations, such as that between psoriasis and cardiovascular disease.

Dr. Lebwohl said, "It would be useful to know whether there is an association between severity of psoriasis and risk for other autoimmune diseases. For the average patient with mild psoriasis, there probably is little need for more extensive testing unless there are also symptoms such as the abdominal pain and gastrointestinal symptoms that might suggest Crohn's disease, but if psoriasis severity turns out to be associated with other autoimmune disorders, we should be ready to order additional testing."

Dr. Lebwohl also noted that psoriatic arthritis and RA are often confused and that differentiating psoriatic arthritis from RA will be an important task in further defining the association of psoriasis with autoimmune diseases.

Shared Genetic or Environmental Cause?

Additional data linking psoriasis to autoimmune diseases were reported in 2 research letters that accompanied the current study and were published in the same issue of the journal.

Leon N. Hsu, BA, and April W. Armstrong, MD, from the University of California at Davis School of Medicine in Sacramento, present a research letter concluding that "the association among psoriasis and [celiac disease], and [inflammatory bowel disease] appears to be well described," but that more work is needed to determine whether an independent association exists between psoriasis and multiple sclerosis, systemic lupus erythematosus, and autoimmune thyroid disease.

Andrew C. Walls, BSc, and Abrar A. Qureshi, MD, MPH, from Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, also published a research letter, in which they report on a chart review of 76 patients with concomitant fibrosing disorders and psoriasis. The authors found a predisposition toward autoimmunity in 38.5% of patients, who had a personal history of a third concomitant autoimmune disease in addition to psoriasis and a fibrosing disorder. The researchers also found that 42.3% of patients reported a first-degree relative with an autoimmune disease.

Dr. Wu and colleagues note that at least 10 non-HLA related risk genes or loci are suspected of contributing to RA, and 6 to psoriasis. "The study suggests a genetic or environmental cause common across autoimmune diseases," the research team concludes. "Further investigation of individuals with multiple autoimmune diseases may yield important clues about the origin and pathogenesis of the disease."

The study was supported by the Kaiser Permanente’s Regional Research Committee. .Dr. Wu received research funding from Abbott Laboratories, Amgen, and Pfizer. One coauthor has received research funding from Procter & Gamble, Janssen, and Genentech. The other authors have disclosed no relevant financial relationships. Dr. Armstrong reported research and consulting fees from Abbott and Centocor. Hsu has disclosed no relevant financial relationships. Dr. Qureshi has received grant funding from Amgen/Pfizer and consulting fees from Abbott, Centocor, Novartis, and the Centers for Disease Control and Prevention. Walls has disclosed no relevant financial relationships.

J Am Acad Dermatol. 2012;67:924-930, 1076-1083. Article abstract, Hsu letter full text, Walls letter full text