Psoriatic arthritis can often go undiagnosed in patients with psoriasis, and an earlier diagnosis is critical to prevent the adverse effects of psoriatic arthritis, according to an expert.
Psoriatic arthritis can often go undiagnosed in patients with psoriasis, and earlier diagnosis is critical to prevent the adverse effects of psoriatic arthritis, according to a staff rheumatologist at Women’s College Hospital in Toronto, Scientist at Women’s College Research Institute, and assistant professor in the department of medicine at the University of Toronto, who spoke at the Atlantic Dermatological Conference in May.
“Psoriatic arthritis is a chronic condition that can be a destructive disease that causes joint damage,” Lihi Eder M.D., Ph.D., tells Dermatology Times. “Arthritis causes a major burden on a patient’s life. It affects mobility, quality of life, and productivity, and there are risks of other co-morbidities like heart disease, diabetes, and depression.”
Indeed, 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 Patients who have psoriatic arthritis compared to patients with only psoriasis had more neurologic diseases, like neuropathy or multiple sclerosis, as well as greater hepatic impairment and gastrointestinal diseases.1
Dr. Eder cites a multi-country prevalence study that involved 949 patients where almost a third of patients with psoriasis seen in dermatology centers had psoriatic arthritis as determined by a rheumatologist. A total of 41% of the 285 patients who were given a diagnosis of psoriatic arthritis had not been supplied with a previous diagnosis of psoriatic arthritis, illustrating under-diagnosis of psoriatic arthritis in patients with psoriasis who had been seen in dermatology clinics.3
A study from Sweden of 197 patients with psoriatic arthritis who were followed for five years concluded that radiography and scoring of the hands and feet at baseline are critical steps and cannot be substituted for clinical signs of disease.4
Next: Diagnostic challenges
There are several reasons why it is a challenge to diagnose psoriatic arthritis, Dr. Eder says. Some of those reasons include the heterogeneity of the condition; that it can be mistaken for conditions like fibromyalgia, osteoarthritis and mechanical back pain; and that it can be difficult to differentiate it from other forms of arthritis.
Moreover, unlike with rheumatoid arthritis, or systemic lupus erythematosus, or systemic vasculitis, no autoimmune diagnostic markers exist that inform the diagnosis of psoriatic arthritis, Dr. Eder explains.
“There is no one particular test (that can be performed) to help physicians (diagnose psoriatic arthritis),” she says.
It is important to note that the severity of psoriasis is not correlated with the presence of psoriatic arthritis, Dr. Eder says.
“Patients may have psoriatic arthritis even though they do not have skin disease when I see them,” she says.
Factors that predict the development of psoriatic arthritis in patients with psoriasis include nail disease, obesity, family history of psoriatic arthritis, and positivity of certain HLA alleles such as HLA-B27.
With an earlier diagnosis of psoriatic arthritis, patients can then get more rapid access to treatments, in particular more novel therapies such as biologic agents, Dr. Eder says. Several biologic medications, including tumor necrosis factor antagonists, IL-23 and IL-17 blockers, and phosphodiesterase-4 inhibitors, are effective in treating psoriasis only and psoriasis with psoriatic arthritis, Dr. Eder says
In a Canadian context, wait times to see a rheumatologist contribute to the delay in diagnosis of psoriatic arthritis. There is a relative shortage of rheumatologists, particular in rural areas of Canada, leading to long wait times for seeing a rheumatologist and delays in diagnosis.
“There is a need to improve the system and develop models of care to improve early detection (of psoriatic arthritis),” Dr. Eder says. “We need to find a better way to triage patients (to improve the range of diagnosis of psoriatic arthritis).”
There is an economic cost to psoriatic arthritis, and that cost rises as a patient’s disease advances and his or her function deteriorates.
Next: New care model
New care model
Dr. Eder is currently involved in a pilot study of an innovative model of care where patients with psoriasis experiencing musculoskeletal symptoms, such as joint pain and stiffness, have direct access to rheumatology care. The model includes a central triage clinic where these patients are screened by other healthcare professionals, such as physiotherapists, and undergo a targeted ultrasound of symptomatic joints to assess if there are any signs of active arthritis.
“We anticipate that this new model of care will improve the early detection of psoriatic arthritis among patients with psoriasis,” Dr. Eder says.
Some of the immunological pathways that are important in rheumatoid arthritis do not play a role in psoriatic arthritis, Dr. Eder says.
“Pathways involving IL-17 and IL-23 are more important in psoriatic arthritis but less important in rheumatoid arthritis,” she says.
Dr. Eder reports no relevant financial relationships.
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.