Psoriasis link to major comorbidities

BEING aware that psoriasis is “more than just a rash” is important says a leading Australian dermatologist in the wake of US research linking the disorder to major medical comorbidities such as diabetes, chronic pulmonary disease and peptic ulcer.

Associate Professor Peter Foley of the University of Melbourne’s department of medicine (dermatology) said he believed the association between psoriasis and several comorbidities was becoming more widely known in the dermatological community, but many other doctors and patients were still not fully aware of the link.

“Psoriasis is now being thought of by those with a particular interest in the disease as being a chronic inflammatory systemic disease that manifests primarily in the skin and in the joints but — just like rheumatoid arthritis and inflammatory bowel disease — the chronic inflammatory load seems to contribute to the development of a number of comorbid states”, said Professor Foley, who is also director of research at the Skin and Cancer Foundation.

Professor Foley was commenting on research published in JAMA Dermatology that found the burden of major medical comorbid diseases increased with the severity of a patient’s psoriasis. (1)

The US population-based cross-sectional study matched 9035 adults with psoriasis with 90 350 adults without psoriasis.

Psoriasis overall was associated with a higher prevalence of chronic pulmonary disease (adjusted odds ratio of 1.08); diabetes mellitus (1.22); diabetes with systemic complications (1.34); mild liver disease (1.41); myocardial infarction (1.34); peptic ulcer disease (1.27); peripheral vascular disease (1.38); renal disease (1.28); and rheumatologic disease (2.04).

The study also revealed significant associations between objectively measured psoriasis severity and each of these comorbidities. The researchers wrote that strong-dose response relationships were demonstrated, with 22% and 32% increases in diabetes, 36% and 87% increases in diabetes with complications, and 39% and 81% increases in aggregated atherosclerotic outcomes among patients with moderate or severe psoriasis, respectively, compared with controls.

Professor Foley said many of the comorbidities identified in the research were already known, such as cardiac disease, diabetes and liver disease. However, he said, there were also some surprises, such as an increased risk of chronic pulmonary disease and peptic ulcer disease with psoriasis.

“It’s easy to be distracted when someone has a significant proportion of their skin covered with a rash, but it really goes back to this idea of treating the whole patient”, he said. “Certainly in [dermatology] clinics around the country where we’re managing moderate-to-severe disease … we are screening people for the common comorbidities and relating anything we find to the patient and their GP to ensure attention is paid to those components as well.”

Earlier this year, a group of experts including Professor Foley published treatment goals for moderate-to-severe psoriasis. Professor Foley told MJA InSight that setting definitions of severity and treatment targets for psoriasis would “refocus dermatologists’ and other medical practitioners’ attention onto this as a significant disease”. (2)

The study authors also recommended doctors keep a close eye on patients with psoriasis, saying doctors “should be aware of these comorbid disease associations to provide comprehensive medical care to patients with psoriasis, especially those presenting with more severe disease”.

Associate Professor Jonathan Shaw, head of clinical diabetes and epidemiology at the Baker IDI Heart and Diabetes Institute, said the JAMA Dermatology study added to the evidence of a link between psoriasis and diabetes, but uncertainty remained about the factors underlying that association.

“It may be that there are pathophysiological links between the conditions — things like inflammation, which is a component of the pathophysiology of type 2 diabetes and is involved in psoriasis”, he said.

Professor Shaw said the study authors acknowledged the possibility of confounding from factors such as smoking and obesity, which were also risk factors for diabetes.

Even so, he said, the study should prompt clinicians to look more closely at patients with psoriasis. “It doesn’t make all that much difference what underlies the association”, he said.

“People with psoriasis perhaps ought to be looked at a little bit more carefully in terms of whether or not they have diabetes and, if they do, how well it is controlled”.

1. JAMA Dermatol 2013; Online 7 August
2. Australas J Dermatol 2013; 54: 148-152