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The patient's history of psoriasis, along with his current skin and scalp plaque flares, symmetrical joint symptomatology, laboratory studies, and x-rays, suggest a diagnosis of symmetrical psoriatic arthritis (PsA). The rheumatologist considers ordering additional imaging to assess for subclinical enthesitis and dactylitis, and discusses treatment next steps with the patient, given inadequate control with a TNF inhibitor.
Symmetrical polyarthritis is one of the most common types of PsA and involves five or more joints in the hands, wrists, ankles, and/or feet. Among patients with PsA, 60% to 80% experience plaque psoriasis before joint-symptom onset; time to joint-symptom onset in these patients typically occurs within 10 years of a plaque psoriasis diagnosis. Involvement of DIP joints differentiates PsA from rheumatoid arthritis, as does the absence of subcutaneous nodules and a negative result for rheumatoid factor. About 30% of all people with plaque psoriasis will develop PsA, which affects an estimated 1 million people in the United States annually. Symptoms typically appear between the ages of 35 and 55 years; women are more likely than men to develop symmetrical PsA.
There are no specific diagnostic tests for PsA. Rheumatologists generally use the assessment known as the Classification Criteria for Psoriatic Arthritis, (CASPAR), which can help reveal established inflammatory articular disease through a point system based on the presence/absence of various factors. On laboratory studies, the most common characteristic abnormalities of PsA are elevated ESR and CRP levels and negative rheumatoid factor in most patients. Other abnormalities that may be present in patients with PsA include elevated serum uric acid concentration and serum immunoglobulin A, and reduced levels of circulating immune complexes. Physicians also use imaging studies, such as radiography, ultrasonography, and MRI, to help differentiate PsA from other articular diseases.
While the pathogenesis of PsA remains unclear, research has shown that disease development is associated with a complex interplay of immune-mediated inflammatory responses; genetic and environmental factors may also be involved. In addition, patients with PsA are more likely to have a high risk for comorbidities, including obesity, type 2 diabetes, hypertension, hyperlipidemia, and cardiovascular events, compared with the general population.
When patients with PsA experience both skin and joint symptoms, a multidisciplinary approach to care is advised. Multidisciplinary teams play a key role in educating patients about their treatment plans and managing their PsA symptoms. The teams also help patients determine the best approaches to exercise to help maintain current joint function, as well as helpful adjustments in daily activities that will make it easier to accommodate their disease.
Nonsteroidal anti-inflammatory drugs, whether self-prescribed or prescribed by a physician, are a common initial treatment to manage joint symptoms of PsA. Current American College of Rheumatology treatment guidelines, however, encourage early treatment with disease-modifying antirheumatic drugs (DMARDs) because approximately 40% of patients with PsA develop erosive and deforming arthritis. Several DMARDs are available, including older drugs like methotrexate, as well as newer biologic agents, such as TNF inhibitors, interleukin (IL)-17 inhibitors, IL-12/23 inhibitors, and Janus kinase inhibitors. In addition, guidelines recommend early and customized physical therapy and rehabilitation approaches for patients with PsA.
Herbert S. Diamond, MD, Professor of Medicine (retired), Temple University School of Medicine, University of Pittsburgh; Chairman, Department of Medicine Emeritus, Western Pennsylvania Hospital, Pittsburgh, PA.
Herbert S. Diamond, MD, has disclosed no relevant financial relationships.
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