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Think beyond guidelines for aggressive subtype of OA.

EXPERT ANALYSIS FROM THE ANNUAL INTERNAL MEDICINE PROGRAM

ESTES PARK, COLO. -- Thinking outside the evidence-based guidelines is the only way to manage erosive, inflammatory osteoarthritis of the hand, which is an aggressive subtype of primary osteoarthritis frequently misdiagnosed as rheumatoid arthritis or psoriatic arthritis.

This inflammatory destructive joint disease accounts for 5%-10% of all cases of primary OA. The inflammation waxes and wanes over the course of years, resulting in knobbly, painful, inflamed knuckles and finger deformities of the distal and proximal interphalangeal joints.

This form of OA most often affects white women in their 40s and 50s. A strong genetic component is involved: Two-thirds of patients with the erosive, inflammatory subtype of OA have a positive family history, Dr. Sterling West noted at a conference on internal medicine sponsored by the University of Colorado.

Misdiagnosis as rheumatoid arthritis or psoriatic arthritis can be avoided by bearing in mind that despite its aggressive nature, inflammatory OA is still a form of OA. As such, the serology is normal: There is no elevation in erythrocyte sedimentation rate or C-reactive protein, and antinuclear antibody and rheumatoid factor testing will be negative. Unlike in rheumatoid arthritis or secondary OA due to hemochromatosis, calcium pyrophosphate disease, or trauma, there is no metacarpophalangeal joint or wrist involvement, stressed Dr. West, professor of medicine and fellowship program director at the university.

X-rays are extremely useful in making the diagnosis. A hallmark of the erosive, inflammatory subtype of OA is the gull-wing sign, a distinctive pattern of central subchondral erosions of the interphalangeal joints evocative of a seagull's wing.

Unfortunately, OA therapy "really hasn't changed in 100 years," according to Dr. West. But the aggressive inflammatory nature of the erosive subtype often necessitates moving beyond evidence-based, guideline-recommended treatment.

While acetaminophen at up to 4 g/day is guideline-endorsed as first-line treatment for OA because it can safely achieve up to about a 30% reduction in pain, it doesn't work as monotherapy in the erosive, inflammatory subtype. It's best paired with other evidence-based therapies: topical 1% diclofenac gel at 2-4 g four times daily and/or an NSAID.

"Salsalate is something that tends to get shunted off to the side. It's certainly not our strongest NSAID, but it is one of our safest ones," the rheumatologist said.

Celecoxib (Celebrex) and other prescription NSAIDs are more potent but pose safety concerns in patients with cardiovascular disease or renal impairment. Under those circumstances, Dr. West tends not to use them, opting instead for tramadol (Ultram) or duloxetine (Cymbalta). There is good evidence for their efficacy in OA, where their pain-modulating effect is achieved via serotonin/norepinephrine reuptake inhibition.

"They're expensive. Insurance companies often will not pay for them. Keep in mind that venlafaxine (Effexor) is another [serotonin/norepinephrine reuptake inhibitor]. And while it's not approved for use in osteoarthritis, it certainly is less expensive and works very similarly to duloxetine and tramadol," according to Dr. West.

His go-to, non-evidence-based therapies for erosive, inflammatory OA include isotoner gloves at night. "The warmth and compression help with morning stiffness," Dr. West explained.

He also recommends application of heated paraffin wax in the morning for the same reason.

Hydroxychloroquine (Plaquenil) often effectively addresses the inflammatory component of the erosive subtype of OA. And intra-articular corticosteroid injections are "a very important treatment" that's safe so long as a joint isn't injected more than three or four times per year, the rheumatologist continued.

Case reports describe treatment success with anakinra (Kineret) and adalimumab (Humira). "This is a very expensive way to go. We don't use that," he said.

Dr. West reported having no conflicts of interest.

Caption: DR. WEST

bjancin@frontlinemedcom.com

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Title Annotation:osteoarthritis; PAIN
Author:Jancin, Bruce
Publication:Family Practice News
Article Type:Disease/Disorder overview
Date:Aug 1, 2013
Words:619
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