Psoriasis is a skin condition with genetic and inflammatory origins. It causes areas of the skin to be reddened, roughened, itchy and topped with coarse silvery scales. The areas where it affects the skin are called plaques, and while it can show up anywhere, it is most likely to affect the elbows, knees, scalp, trunk and fingernails. The association between psoriasis and arthritis has been recognized for years, but more recently a new relationship has emerged, one between psoriasis and type 2 diabetes.
In 2012, the results of a large cohort study involving 184,395 participants sponsored by Brigham and Women’s Hospital and Harvard Medical School, as well as the Harvard School of Public Health, were released. The study found that psoriasis was an independent risk factor for type 2 diabetes, and that the relationship was especially strong for people who were higher on the body mass index, and for women under the age of 60. In addition, the more surface area of the body that was affected by psoriasis, the greater the degree of risk for type 2 diabetes .
The link between psoriasis and type 2 diabetes may have to do with genes. A 2014 study of the variants of the IL 12/23 genes in 405 Spanish psoriasis patients revealed a variation that was strongly linked with the severity of psoriasis, another that was linked with psoriatic arthritis and two more that were linked with type 2 diabetes .
Ongoing research has helped to further define the physiological commonalities between psoriasis and type 2 diabetes. For example, in a review published in the Journal of Diabetes Research & Clinical Metabolism in 2014, the authors note psoriasis is now seen as a systemic illness, not just a disease of the skin, and one in which insulin resistance is present. In fact, insulin resistance may trigger aberrant behaviour in certain skin cells, giving rise to psoriasis . The presence of insulin resistance is also a major feature in the development of type 2 diabetes .
What this means for people living with psoriasis is that greater attention must be paid to diet, stress management and exercise as factors which influence, and could prevent, insulin resistance in light of the significantly higher risk for psoriatics to develop type 2 diabetes.
 Li, Wenqing, et al. “Psoriasis and risk of type 2 diabetes among women and men in the United States: a population-based cohort study.” J Invest Dermatol 132.2 (2012): 291-298.
 Eirís, Noemí, et al. “Genetic variation at IL12B, IL23R and IL23A is associated with psoriasis severity, psoriatic arthritis and type 2 diabetes mellitus.” Journal of dermatological science 75.3 (2014): 167-172.
 Sliem, H. A., et al. “Psoriasis and Insulin Resistance: Is there a Relationship.” Int J Endocrinol Metab Disord 2.2 (2016).
 Fitzgerald, Rhea, et al. “Psoriasis and insulin resistance: a review.” journal of Diabetes Research and Clinical Metabolism3.1 (2014): 3.