NEW ORLEANS – Think of psoriasis as a systemic disease whose key extracutaneous sites of involvement include the eyes, joints, and perhaps the coronary arteries, although that remains controversial.

"Psoriasis is an inflammatory condition that flows far beyond the skin," Dr. Brian F. Mandell stressed at the annual meeting of the American Academy of Dermatology.

Dr. Mandell, professor and chairman of the department of medicine at the Cleveland Clinic, offered a rheumatologist's perspective on a disease whose full range of expression extends well afield of daily dermatologic practice.

Psoriatic uveitis. This uncommon disease manifestation affects only about 2% of psoriasis patients, but it's often insidious in onset and can result in irreversible loss of vision.

Psoriasis-associated uveitis can be either anterior or posterior. The anterior uveitis tends to be painful and often produces a minimally red and irritated eye. In contrast, posterior uveitis is often essentially devoid of symptoms other than perhaps floaters or a bit of blurring. Psoriasis-associated uveitis is more like the uveitis associated with inflammatory bowel disease than the classic HLA-B27-associated form of uveitis.

"Be wary of any eye complaints, and be very liberal in referring to ophthalmology for a slit-lamp exam," he advised.

Psoriatic joint disease. Two forms of joint disease are of particular relevance to the psoriatic population. One is the increased incidence of gouty arthritis in patients with the skin disease.

"The challenge here is to distinguish between gout and what appears to be a totally typical flare of psoriatic monoarticular arthritis. As a dermatologist, what you should expect from a rheumatology colleague in that setting is for us to stick a needle in the joint and make that distinction, because otherwise there's no way that distinction can be made with certainty. Patients tend to be hyperuricemic when they have psoriasis, so you can't use a laboratory test to make the distinction," Dr. Mandell explained.

The occurrence of psoriatic arthritis is, rather surprisingly, unrelated to the severity of the skin disease. Nor is psoriatic arthritis strongly associated with nail involvement. The most important patterns of psoriatic arthritis include spondylitis, enthesitis, and peripheral arthritides.

The hallmark of spondylitis is morning stiffness and pain lasting for several hours. That's the key distinguishing feature separating inflammatory from mechanical back pain – and it's a complaint that definitely warrants sending a psoriasis patient to a rheumatologist, in Dr. Mandell's view.

Enthesitis involves inflammation where tendons and ligaments join to the bone. Common manifestations in patients with psoriatic arthritis include hip pain or pain on the outside of the knee. The onset is often subtle. Successful treatment requires high-intensity anti-inflammatory therapy; enthesitis does'’t respond well to pain medications.

In contrast to the subtleties of psoriatic enthesitis, psoriatic peripheral arthritis is generally a dramatic condition marked by impressive fluid accumulation. In dactylitis, the entire digit, not just a joint, is swollen and strikingly painful; this is the sausage digit. And unlike rheumatoid arthritis, psoriatic dactylitis occurs asymmetrically.

"Rheumatoid arthritis just doesn't do this. There are very few 'nevers' in medicine. But I've never seen rheumatoid arthritis take the form of a true dactylitis. When you see it in the absence of skin disease, as a rheumatologist I'm actually going to undress the patient and go looking for skin disease," Dr. Mandell said.

Like psoriatic enthesitis, psoriatic dactylitis responds well to full-dose anti-inflammatory medication, he added.

Very few inflammatory arthritides target the distal interphalangeal joints. Psoriatic arthritis is far and away the most common one. This is an exceedingly destructive disease process over time, and it warrants very aggressive treatment.

Methotrexate is "reasonably effective" for all forms of psoriatic arthritis except spondylitis, according to Dr. Mandell. Anti–tumor necrosis factor biologics are strikingly effective for all manifestations of psoriatic arthritis; often lower doses are required than for treatment of skin disease.

Coronary artery disease. There's no question that psoriasis patients have an increased prevalence of the metabolic syndrome. And epidemiologic studies also demonstrate that they are at increased risk for CAD and cardiovascular events. But whether psoriasis constitutes an independent risk factor for acute ischemic heart disease or the increased risk is due to the high prevalence of traditional coronary risk factors in psoriasis patients remains a topic of active debate in both the dermatologic and internal medicine literature.

"Whether psoriasis is directly causative or merely an association I don't think really matters," Dr. Mandell asserted. "When you have a patient with psoriasis in front of you, you need to take advantage of a teaching moment. They're naked, they’re glowing in the dark from their psoriasis, and this is an opportunity to let them know there probably is a cardiovascular risk and they should be seeing their primary care provider to make sure their modifiable cardiovascular risk factors like lipids, hypertension, and smoking have been addressed. In that way you've done your job the same way I’ll do my job in similar settings when I see a patient with rheumatoid arthritis or psoriatic arthritis."

Dr. Mandell said that he has no relevant financial interests.

Be Attuned to Extracutaneous Manifestations of Psoriasis