Psoriatic arthritis (PsA) can often go undiagnosed in patients with psoriasis which, as physicians know, can negatively affect long-term outcomes.
Musculoskeletal conditions have a window of opportunity for treatment. If treated early, most disorders, such as psoriatic arthritis can go into remission, but if a diagnosis comes too late, joint damage can become irreversible. The condition can be complicated by a host of comorbidities which, when left untreated, hastens poor outcomes.
In one psoriatic arthritis comorbidity study, hypertension was present in 37% of psoriatic arthritis patients while it was present in only 20% of patients who had psoriasis only.1 Type II diabetes mellitus and obesity were also more common in patients with psoriatic arthritis than in patients with psoriasis only.2 Psoriatic arthritis patients reportedly have more hepatic impairment, gastrointestinal diseases and neurologic diseases — such as neuropathy or multiple sclerosis — as compared to patients with psoriasis only.1
“Patients may have psoriatic arthritis even though they do not have skin disease,” said Lihi Eder M.D., Ph.D., a rheumatologist with Women’s College Hospital in Toronto, who spoke on this subject at the Atlantic Dermatological Conference in May.
Dr. Eder cites a multi-country prevalence study in which nearly one-third of 949 psoriasis patients were also diagnosed with psoriatic arthritis. However, the severity of psoriasis does not necessarily indicate the simultaneous presence of psoriatic arthritis.
Psoriatic arthritis is a heterogeneous condition that can be difficult to diagnose. It can be mistaken for other conditions such as fibromyalgia, osteoarthritis and mechanical back pain. Plus, it can be difficult to differentiate it from other forms of arthritis.
Unlike in rheumatoid arthritis, systemic lupus erythematosus or systemic vasculitis, there are no autoimmune diagnostic markers that can inform the diagnosis of psoriatic arthritis, Dr. Eder said. In the absence of a definitive diagnostic marker for psoriatic arthritis, physicians rely on symptoms and the patient’s medical history to aid in a diagnosis. For example, it is known that psoriasis patients with nail disease, obesity, a family history of psoriatic arthritis, and positivity for certain HLA alleles, such as HLA-B27, may be more susceptible to developing psoriatic arthritis.
A five-year long Swedish study of 197 patients with psoriatic arthritis found that radiography and scoring of the hands and feet at baseline were critical steps in the diagnosis process and cannot be substituted for clinical signs of disease.4
Treatment elusive for some
Recent studies have shown that diagnosing and treating the disease early can lead to better long-term in outcomes, but that can be challenging. A physician shortage here in the United States and Canada has made it difficult to see a doctor early, especially in underserved areas. So, despite the availability of life-saving medicines, such as TNFi treatments, IL-23 and IL-17 blockers, and phosphodiesterase-4 inhibitors, obtaining treatment remains elusive for some out-of-reach patients.
“There is a need to improve the system and develop models of care to improve early detection. We need to find a better way to triage patients,” Dr. Eder said.
Dr. Eder is currently involved in a pilot study in which psoriasis patients with musculoskeletal symptoms, such as joint pain and stiffness, have access to rheumatology care. The model includes a central triage clinic where patients are screened by healthcare professionals and undergo a targeted ultrasound of symptomatic joints to assess for signs of active arthritis.
“We anticipate that this new model of care will improve the early detection of psoriatic arthritis among patients with psoriasis,” she said.
1Husted JA, Thavaneswaran A, Chandran V, et al. Cardiovascular and other comorbidities in patients with psoriatic arthritis: a comparison with patients with psoriasis. Arthritis Care & Research (Hoboken). 2011 Dec;63(12):1729-35.
2Kraishi M, MacDonald D, Rampakakis E, Vaillancourt J, Sampalis JS. Prevalence of patient-reported comorbidities in early and established psoriatic arthritis cohorts. Clinical Rheumatology. 2011 Jul;30(7):877-85.
3Mease PJ, Gladman DD, Papp KA, et al. Prevalence of rheumatologist-diagnosed psoriatic arthritis in patients with psoriasis in European/North American dermatology clinics. Journal of the American Academy of Dermatology. 2013 Nov;69(5):729-35.
4Geijer M, Lindqvist U, Husmark T, et al. The Swedish Early Psoriatic Arthritis Registry 5-year Followup: Substantial Radiographic Progression Mainly in Men with High Disease Activity and Development of Dactylitis. The Journal of Rheumatology. 2015 Nov;42(11):2110-7.