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Psoriasis and Psoriatic Arthritis: Observational Studies

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Psoriasis is characterized by red scaly patches on the skin, but this autoimmune disease is more than skin deep. It is associated with pain, physical disability, psychological distress, and increased risk of heart disease, cancer, and infections.

Sue Langham of PHMR consulting, London, UK, and colleagues provided a review.

Psoriatic arthritis is the most common condition linked to the skin lesions of arthritis. This may lead to joint destruction, cartilage deterioration, bone damage, and joint fusion.

The U. S. National Library of Medicine's PubMed web site lists treatment options for psoriasis and psoriatic arthritis as:

1. Topical therapies including lotions, ointments, and shampoos containing cortisone, coal tar, and moisturizers
2. Phototherapy with ultraviolet A or B light
3. Immunomodulatory drugs such as methotrexate and cyclosporine
4. Biologic drugs including adalimumab (Humira), alefacept (Amevive), etanercept (Enbrel), infliximab (Remicade), and stelara

Langham reported that these treatments have demonstrated efficacy in randomized, controlled trials. However, more data are needed on how they work in ordinary patients.

Langham explained, “efficacy assesses whether an intervention works under optimal circumstances, whereas effectiveness assesses whether an intervention works in usual care.” Observational studies are important to evaluate effectiveness.

Langham's review of the literature demonstrated that more data are needed to cover the wide variety of cases. Psoriasis is the most common autoimmune disease in the United States, and affects 2 to 3 percent of the world population.

The National Psoriasis Foundation conducts annual surveys to help fill the need for more data. The current survey revealed that up to 2 million people are already diagnosed with psoriatic arthritis, and the true number of cases may be much greater. The 2011 Survey Panel Snapshot reported, “Nearly one in four people with psoriasis may have undiagnosed psoriatic arthritis.”

The survey reported significant impact of psoriatic arthritis on quality of life:

63 percent of respondents are unable to be as active as they used to be.
47 percent say their condition has affected their ability to work.
34 percent have trouble getting in and out of a car.
34 percent have stiffness for more than two hours after waking up.

See your doctor if you're interested in research opportunities.


1. Langham S et al, “Large-scale, prospective, observational studies in patients with psoriasis and psoriatic arthritis: A systematic and critical review”, BMC Medical Research Methodology 2011; 11:32. http://www.ncbi.nlm.nih.gov/pubmed/21453459

2. PubMed Health. Psoriasis. Web. Oct. 12, 2011.

3. 2011 Survey Panel Snapshot from the National Psoriasis Foundation. Web. Oct. 12, 2011.

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Reviewed October 25, 2011
by Michele Blacksberg RN
Edited by Jody Smith

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We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.



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