Severe Psoriasis Amplifies Immunoglobulin A Nephropathy Risk

Miriam E. Tucker

March 10, 2016

WASHINGTON, DC — The risk for immunoglobulin (Ig)A nephropathy is five times higher in people with severe psoriasis than in those without. And the risk for overall glomerular disease is two times higher.

These findings come from an analysis of data from The Health Improvement Network in the United Kingdom.

"Given these associations, it would be reasonable to suggest keeping tabs on these lab values, at least in patients with moderate to severe disease," Sungat Grewal, BS, a medical student and predoctoral fellow at the University of Pennsylvania Perelman School of Medicine in Philadelphia.

In a previous study of the network data, an elevated risk for chronic kidney disease was seen in patients with moderate to severe psoriasis, as reported by Medscape Medical News (BMJ. 2013;347:f5961).

There have also been case reports of a link between psoriasis and IgA nephropathy, but this is the first large-scale investigation to determine which specific kidney diseases are responsible for the finding of overall chronic kidney disease, Grewal explained.

She presented the findings during a late-breaking session here at the American Academy of Dermatology 74th Annual Meeting.

Common Cause of Glomerulonephritis

IgA nephropathy, which affects about one in 100,000 people annually in the United States, is the most common cause of glomerulonephritis. It typically presents as an acute mucosal infection that progresses to visible blood in urine in a few days. In 20% to 40% of patients, it leads to end-stage renal disease.

Grewal and her colleagues examined 1994 to 2014 data from electronic medical records in the database. The cohort of more than 11 million individual patients was broadly representative.

The team used diagnostic codes to identify 193,013 patients with mild psoriasis and 12,806 with severe psoriasis. Each patient was matched with up to five control subjects from the same clinical practice who did not have psoriasis.

The psoriasis patients tended to be younger, more obese, and more likely to drink or smoke than the 1,019,142 control subjects. They also had more comorbidities.

The risk for IgA nephropathy was almost five times higher in patients with severe psoriasis than in control subjects (hazard ratio [HR], 4.75) in a fully adjusted model for age, sex, body mass index, drinking and smoking status, socioeconomic status, hypertension, diabetes, hyperlipidemia, cardiovascular disease, arthritis, viral infection, psoriatic arthritis, and the use of nonsteroidal anti-inflammatory agents.

In addition, the risk for glomerular disease was more than two times higher in patients with severe psoriasis (HR, 2.05).

The risks for IgA nephropathy and glomerular disease were not significantly different between patients with mild psoriasis and control subjects.

However, the elevated risk for IgA nephropathy associated with severe psoriasis is still quite low, at about one case per 8888 patients annually. As a comparison, Grewal reported that the incidence of spontaneous triplets is about one per 8000 natural pregnancies.

Nonetheless, she said, "I think an awareness of the comorbidities is important so you can educate your patients on what they should be looking out for, and you can monitor them over time."

We don't understand why it's happening, we just know there's an association.

"It is still very unlikely," said Inder Dhillon, MD, a dermatologist at the Kaiser Permanente Medical Group and clinical instructor at the University of California, San Francisco. "We have to keep it in perspective."

"But it's very useful to know that IgA nephropathy is what patients are actually at increased risk for, and it behooves us to remember that," he told Medscape Medical News.

"We don't understand why it's happening, we just know there's an association, said Grewal. "Is it because they're at a higher risk for developing specific renal diseases, or because once they have renal disease they're at a higher risk for progressing to chronic kidney disease?"

Some of the theories put forward have been a hyperfunctioning immune system, impaired mucosal integrity that exposes immunoglobulin-stimulating antigens, and a genetic predisposition toward defective immunoglobulin that deposits in glomeruli.

We must treat psoriasis aggressively and not dismiss it as just a skin disease.

Regardless, she pointed out, "our work supports the idea that psoriasis is a disease that is systemic, not limited to the skin."

"We always knew that diseases inside the body manifest in the skin, but only recently has it been understood that severe skin disease, especially psoriasis, goes deep inside the body and hurts organs inside the body. It's an evolving field," said Dr Dhillon.

"The most important point is not just to tell patients all the extra diseases they're at risk for, but to aggressively treat psoriasis to decrease the risk for these other complications," he added. "We must treat psoriasis aggressively and not dismiss it as just a skin disease."

The study was funded in part by an educational grant from Pfizer to the trustees of the University of Pennsylvania. Ms Grewal and Dr Dhillon have disclosed no relevant financial relationships.

American Academy of Dermatology (AAD) 74th Annual Meeting. Presented March 6, 2016.

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