Psoriasis was regarded as a chronic recurrent disorder developing only in the skin for several decades, before it was demonstrated to be associated with joint manifestations in 1960s. Although many non-cutaneous disorders were reported to occur concomitantly with psoriasis, whether they were coincidental or truly associated with psoriasis remained uncertain until recently. At the turn of 21st century, a more robust epidemiological research in the form of prospective cohort studies and cross-sectional studies undertaken in large sample sizes began to portray psoriasis as a multi-system disorder involving the metabolic systems. Obesity was reported to be a risk factor for psoriasis development as well as to be correlated with psoriasis activity1,2. Subsequently, many obesity-related metabolic derangements such as glucose intolerance, hyperlipidemia and hypertension were shown to be correlated with psoriasis3,4. Since such disorders present risk factors in the development of cardiovascular disorders5,6, it is not surprising that patients with psoriasis have shown an increased incidence of cardiovascular events including acute myocardial infarction. Currently psoriasis is not just a quality-of-life-impairment disorder but a quantity-of-life-compromised disorder. Obesity is a serious health issue not only in its individual aspects but also in terms of social health. The Asian region, including the countries Japan and Korea, has been regarded as less problematic for obesity at least in a relative sense. As clinicians, we have not had a solid perception of an association between psoriasis and obesity. Such has prompted our investigation into an association between psoriasis and obesity and psoriasis and metabolic derangements.

We intended for a pilot study before performing a large sample-sized, multi-organ based epidemiological investigative study. We compared body mass index (BMI) of psoriasis patients with that of control group and measured fasting blood sugar level, blood pressure and lipid profiles. The results were compared with those of normal control group.

This study was designed as a retrospective cross-sectional study based on the database of Samsung Medical Information System (SMIS). The SMIS system is a type of electrical medical records system, where a digital database of age, sex, telephone number, vital signs, current medications and medical history may be obtained.

Case group was composed of patients with a diagnosis of psoriasis at the Samsung Medical Center (Seoul, Korea) from January 1, 2008 to April 10, 2009. The patients were investigated for BMI, Psoriasis Area and Severity Index (PASI), blood pressure, serum lipid profiles (total cholesterol, triglyceride; high density lipoprotein [HDL]-cholesterol, low density lipoprotein [LDL]-cholesterol), liver enzymes (aspartate aminotransferase, alanine aminotransferase) and fasting glucose.

Non-psoriatic control group I patients were defined as patients who visited our Dermatology Outpatient Clinic between April 27, 2009 and April 30, 2009. Psoriasis patients and other chronic inflammatory patients were excluded. We measured BMI for non-psoriatic control group I patients.

Non-psoriatic control group II patients were defined as patients who had routine check-ups at the Health Promotion Center of the Samsung Medical Center from January 2009 to April 2009. The group II control patients had no significant medical issues.

According to previous reports7,8, incidence of metabolic syndrome may be restricted to patients with severe psoriasis. Those with metabolic abnormalities showed a poor response to the treatment compared to those without metabolic disorders. Therefore, we investigated the treatment response to cyclosporine according to the BMI status. In the case group, we included 38 patients on cyclosporine (4 mg/kg/d). Among 38 patients who were treated with cyclosporine, a treatment response based on monthly PASI score was evaluated in 32 patients.

Statistical analysis was performed to compare the difference of variables between psoriasis group and control groups. SPSS software was used for the analysis (SPSS version 12.0.1; SPSS Inc., Chicago, IL, USA). Chi-square tests were used to compare categorical parameters between the groups, and t-tests were used to compare continuous parameters. In all cases, p-values less than 0.05 were considered to be statistically significant.

This study was approved by the Institutional Review Board of Ethics Committee of Samsung Medical Center (2010-12-064).

Psoriasis is considered a chronic inflammatory disease characterized by persistent inflammation, and many diseases fall into the category. Some examples of chronic inflammatory disorders include chronic obstructive pulmonary disease, lupus erythematosus and vasculitis. According to recent reports, obesity and atherosclerosis, which are two characteristic findings of metabolic syndrome, are also considered to be chronic inflammatory diseases. There have been various reports investigating the association between psoriasis and metabolic syndrome. Many reports have outlined an increased risk of hypertension, metabolic syndrome, myocardial infarction, diabetes mellitus and insulin resistance in severe psoriasis patients, especially in a young adult group. A number of etiologies may cause increased metabolic abnormality and adverse cardiac event including decreased physical activity, hyperlipidemia, psychological stress, smoking habit and hyperhomocysteinemia. These findings are readily observed in patients with psoriasis7.

Previous studies linking psoriasis with various metabolic abnormalities have been carried out, mostly in Western countries5,7-12. In contrast to studies in Western populations, several investigations based in few Asian countries, including Japan13, Taiwan14 and South Korea15, have shown no significant difference in the incidence of metabolic syndrome between psoriasis patients and control group. Such is consistent with our results.

These observations may suggest that in Asian patients, including Korean patients, there may be no association between psoriasis and metabolic syndrome. This conflicting finding may be a result of the difference of severity of obesity and metabolic syndrome between the Western and Asian populations. It is uncommon to find a person with BMI over 30 in Asian countries, due to different lifestyles including eating habits, physical activity and genetic background. Although the prevalence of metabolic syndrome is increasing in Asian countries, the severity and tendency toward metabolic syndrome is much less apparent when compared to the Western countries.

According to a previous report, the severity of psoriasis is associated with metabolic syndrome in a dose-response manner. Based on this explanation, and considering that the mean BMI of Asian countries is lower than that of the Western countries, we can explain the psoriasis patients in Korea with high PASI score being uncommon.

Interestingly, there was no difference in the treatment response of psoriasis, between the high BMI group and low BMI group of psoriasis patients. This result is not consistent with previous reports5,8,9, and suggests that BMI may not be an appropriate way to measure obesity or metabolic status in Korean patients. However, a small sample size and retrospective nature of our study requires further investigation to elucidate the different results.

In this pilot study, we tried to compare BMI, fasting glucose, blood pressure, lipid profiles between psoriasis patients and control groups. We also tried to compare treatment response to cyclosporine according to BMI in psoriasis patients in the Republic of Korea. A larger sample-sized, multi-organ based prospective studies are needed to demonstrate the relationship between psoriasis and metabolic abnormalities.