WASHINGTON – Another population-based study has found a link between severe psoriasis and kidney disease – this one discovering almost a fivefold increase in the risk of immunoglobulin A nephropathy (IgAN) and a doubling in the risk of glomerular disease.
The findings suggest yet again that psoriasis is a systemic illness, and not something that affects only the skin, Sungat Grewal said at the annual meeting of the American Academy of Dermatology.
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“Numerous case reports have generated a hypothesis that psoriasis may be associated,” with an increased risk of IgAN, said Ms. Grewal, of the department of dermatology at the University of Pennsylvania, Philadelphia. “Our study is the first to test this, and it supports the notion that this is no coincidence. Now we need further research to determine if this association is due to causality or to a shared pathophysiology.”
The link between psoriasis and kidney disease has long been noted, but the first study formally investigating this association was published in 2013 (BMJ. 2013 Oct;347:f5961). The study, also conducted by University of Pennsylvania investigators, used a large patient database in the United Kingdom, matched about 143,000 patients with psoriasis with up to five controls without psoriasis each, and found the risk of chronic kidney disease was nearly doubled for those with severe psoriasis (hazard ratio, 1.93).
A similar finding emerged from Taiwan in 2015. Using the national healthcare database, researchers matched about 4,600 patients with psoriasis with about 923,000 controls. They found that having severe psoriasis was associated with almost a doubling in the risk of chronic kidney disease (HR, 1.90) and almost a tripling in the risk of end stage renal disease (HR, 2.97), after adjusting for age, gender, comorbidities, and use of nonsteroidal anti-inflammatory drugs (J Dermatol Sci. 2015 Jun;78[3]:232-8).
Ms. Grewal and her coinvestigators used data from The Health Improvement Network in the United Kingdom – the same database used in the 2013 study. The study group comprised 206,000 patients with psoriasis and about 1 million controls.
In the overall group of patients, the risk of IgAN was not significantly increased. Nor was there a significant overall association with glomerular disease. And when the group was divided by disease severity, there were no significant associations with either IgAN or glomerular disease in the group with mild psoriasis.
Among those with severe psoriasis, however, the risk of IgAN was almost five times higher (HR, 4.75) and the risk of glomerular disease was doubled (HR, 2.05).
But although the hazard ratios look impressive, the clinical reality shouldn’t spark too much concern, Ms. Grewal said. “To keep things in context, it’s very important to remember that the excess risk of nephropathy attributed to severe psoriasis was still quite small – similar to the chance of a spontaneous pregnancy resulting in triplets.”
Still, she said, the link is intriguing, and something clinicians should keep in mind when managing patients with severe psoriasis.
Ms. Grewal had no financial disclosures. She is a medical student at the Commonwealth Medical College (Scranton, Pa.), and is currently spending a year at the Gelfand Clinical Research Lab at the University of Pennsylvania, Philadelphia.