In a new study, moderate to severe cases of psoriasis were linked to an increased chance of developing chronic kidney disease (CKD).
According to the researchers, patients who have psoriasis — a condition characterized by patches of red, itchy skin — on more than 3 percent of their body should be monitored more closely for kidney problems.
"See a doctor regularly if you have psoriasis."
This study — which was conducted by Joel M. Gelfand, MD, MSCE, associate professor of Dermatology and Epidemiology at the University of Pennsylvania, and colleagues — looked at the risk of developing chronic kidney disease among patients with psoriasis, an inflammatory skin disease that causes redness and itchy skin in 2 to 4 percent of the population.
The researchers looked at electronic medical records of more than 136,500 adult patients in the UK with mild psoriasis and 7,354 patients with severe cases.
To compare results, psoriasis patients were matched by age and practice to about 690,000 patients who did not have the skin condition.
The researchers tracked whether patients had kidney disease, and if so, the severity of the disease. Disease levels were categorized as moderate to advanced.
Patients' age and the severity of their psoriasis, as defined by the total area of the skin affected by the condition, were also recorded.
The researchers found that patients with severe psoriasis were about 93 percent more likely than non-psoriasis patients to develop kidney disease.
Overall, patients with psoriasis were about 5 percent more likely than those without the skin condition to have chronic kidney disease.
Patients with mild cases of psoriasis, however, had about the same chance of developing kidney disease as non-psoriasis patients.
When taking age into account, the researchers found that severe psoriasis patients who were 60 years of age had a two-fold increased risk of developing kidney disease compared to those without psoriasis. And severe psoriasis patients who were 30 years of age were almost four times as likely to develop kidney disease.
When considering the amount of skin affected by psoriasis, mild cases that covered less than 2 percent of the body were about 11 percent less likely to develop kidney disease than non-psoriasis patients.
At the same time, moderate and severe psoriasis cases covering more than 3 percent of the body were 36 percent and 58 percent more likely, respectively, to develop kidney disease than non-psoriasis patients.
"The combined results indicate that, although no association is seen in patients with truly mild disease (less than 2 percent body surface area affected)...associations are seen in moderate and severe psoriasis, which are estimated to affect over 20 percent of patients with psoriasis worldwide," the researchers wrote in their report.
The researchers also wrote that increased screening efforts can help doctors detect and intervene early on to reduce related illnesses and death linked with chronic kidney.
The authors noted a couple of limitations of their study, including that psoriasis cases and their severity might have been classified incorrectly when recorded in the medical records.
Another limitation was that patients could have been screened more often for kidney disease.
The researchers wrote that future research is needed to see how psoriasis treatments affect the risk for chronic kidney disease.
This study was published online October 15 in BMJ.
The research was supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Heart, Lung and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases.
A few of the authors have received research grants and honorariums from the NephCure Foundation-American Society of Nephrology, National Kidney Foundation, Amgen, Abbvie, Celgene, Eli Lilly, Jansen, Novartis, Merck and Pfizer.