Psoriatic arthritis (PSa) is one of the most common forms of inflammatory arthritis with prevalence varying in the general population from 0.3% to 1%. It is unique in that the immune abnormality underlying the condition affects both the skin as well as the joints.

While psoriatic arthritis may begin by attacking only a few joints, over time it may begin to involve many joints and becomes very severe in at least 20% of patients.

Treatment should target the skin and joint problems of the disease simultaneously.

Successful treatment of PsA with conventional therapies is limited by a number of different factors, including failure to effectively manage skin and joint aspects of the disease, risk of potentially serious adverse effects, and poor tolerability.

The usual starting regimen given to patients with PsA is non-steroidal-anti-inflammatory drugs (NSAIDS).

While initial treatment with NSAIDs may control PsA, some patients may experience a worsening of psoriasis and others may not respond well enough.

In addition, NSAIDs do not slow down the course of the disease or prevent development or progression of erosions (joint damage).

Psoralen plus ultraviolet light (PUVA) and other medications may be effective therapies for psoriasis, but they do not halt progressive joint damage and deterioration in patients with PsA.

Usually, patients with severe PsA are placed on disease-modifying anti-rheumatic drugs (DMARDS). These drugs work slowly to retard the progression of disease.

Data from clinical trials support the use of sulfasalazine for PsA. However, a large percentage of patients (approximately 40 % or higher) either do not tolerate the drug or develop side effects.

Methotrexate (MTX) may be a useful drug in PsA patients. The major concern with this drug is potential liver toxicity.

In addition to periodic (monthly) liver function tests, a complete blood cell count and kidney function tests should be obtained during therapy.

Patients with psoriasis receiving MTX appear to be at slightly higher risk for liver disease compared with patients with RA who take the drug. The role of liver biopsy in monitoring is still undecided.

Another drug that has been used is cyclosporine A. While effective, it has many serious toxicities including kidney damage and hypertension.

All of these drugs, in addition to their toxicities, have limited effectiveness in patients who have spinal involvement from their psoriatic arthritis.

Currently, it is felt that institution of drugs that inhibit tumor necrosis factor (TNF) is the recommended course of action to follow. TNF is a chemical messenger that initiates and perpetuates inflammation and destruction in arthritis.

There are three TNF inhibitors that are currently used for psoriatic arthritis. They include etanercept (Enbrel), infliximab (Remicade), and adalimumab (Humira). All three drugs work well for both the rash as well as the joints. Enbrel and Humira are self-administered while Remicade is given by intravenous infusion. These drugs also appear to be effective for the spinal manifestations of psoriatic arthritis.

Other drugs such as rituximab (Rituxan) and abatacept (Orencia) are also being studied for use in psoriatic arthritis.

Patients with painful swollen joints may require intraarticular joint injections with glucocorticoids ("cortisone")