One common form of arthritis that has been relatively ignored until recently is psoriatic arthritis. It is a systemic inflammatory destructive form of arthritis that is perhaps second only to rheumatoid arthritis in its ability to cause disability.
It is often described as a mixed disease since unlike rheumatoid arthritis which is purely a destructive breakdown disease that causes bone loss, joint erosions, and joint destruction, psoriatic arthritis (PA), also causes new bone formation.
The types of systemic features that accompany this condition are also unique in that inflammatory bowel disease, eye inflammation (uveitis), and psoriasis tend to accompany this type of arthritis.
Another unique feature of the disease is the presence of enthesopathy, a localized inflammation at the site where the tendons attach to bone. Areas where this commonly occurs are the Achilles tendon, lateral epicondyle of the elbow, iliac crest, patellar tendon of the knee, plantar fascia of the heel, and the lateral hip.
In addition, PA often presents with a peculiar condition called dactylitis. This occurs when the joints and tendon of a single digit or a few digits become acutely inflamed. This presentation is a hallmark of the disease.
Patients with PA also have co-morbid conditions that can affect the disease. Examples include, high blood pressure, obesity, diabetes, elevated lipids, and heart disease.
Treatments for psoriatic arthritis are not nearly as agreed upon as those for rheumatoid arthritis.
While non-steroidal anti-inflammatory drugs (NSIADS) may be useful for early symptomatic relief, they are ineffective in regards to slowing disease progression.
Second line drugs, called disease-modifying anti-rheumatic drugs (DMARDS), while often used in a similar fashion to the way they're used in rheumatoid arthritis, are not nearly as effective. For example, the DMARD of choice in rheumatoid arthritis is methotrexate. While this drug works in some cases of psoriatic arthritis, its results are not as predictable. Also, it appears that patients with this condition may be at more risk for liver toxicity due to methotrexate.
Plaquenil, another DMARD that is used for RA, rarely is effective for the disease.
Sulfasalazine (Azulfidine), has been used with some success but again, the results are not as predictable or dependable.
The only group of medicines that appears to work well for psoriatic arthritis in a predicable fashion are the TNF inhibitors. There is some debate that certain TNF inhibitors work better for the skin than others. This is the subject of continued investigation.
Other biologic treatments are in the pipeline.