Therapeutic Insights: Links Between Psoriasis and Psoriatic Arthritis

 Joseph F. Merola, MD, MMSc, is an associate professor in the department of dermatology and department of medicine, division of rheumatology, at Harvard Medical School, Brigham and Women’s Hopsital in Boston, MA. He leads the Center for Skin and Related Musculoskeletal Diseases. He is on the Scientific Board of the National Psoriasis Foundation (NPF), founding president of the Psoriasis and Psoriatic Arthritis Clinics Multicenter Advancement Network Consortium (PPACMAN), and the executive committee of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA).

Seoyoung C. Kim, MD, ScD, MSCE, is an associate professor of medicine at Harvard Medical School in Boston, MA. She is the director of program in Rheumatologic, Immunologic, and Musculoskeletal PharmacoEpidemiology (PRIME) in the division of pharmacoepidemiology and pharmacoeconomics while coappointed in the division of rheumatology, inflammation, and immunity at the Brigham and Women’s Hospital. Her research focuses on comparative safety and effectiveness of medications for the rheumatic diseases in addition to health services and outcome research in rheumatology.

Both Dr Merola and Dr Kim joined The Dermatologist to offer insights and highlight the links between psoriasis (PsO) and psoriatic arthritis (PsA).

Briefly, what is known about the relationship between PsA and PsO?
Dr Merola: There is a strong association between PsO and PsA. Up to 30% of our patients with PsO develop PsA. There are strong genetic associations, including a subset of overlapping genetic risk between those with PsO and PsA that may at least partially explain the coprevalence of disease. We also know that certain phenotypes of PsO may be at increased risk for PsA, such as those with scalp, nail, and inverse/intertriginous psoriasis, as well as those with a first-degree relative with PsA, higher skin severity of disease, and other factors.

Given that there is no standard diagnostic test, what questions can dermatologists ask to help identify PsA? Are there any screening tools you would recommend incorporating into derm practice?
Dr Merola: The mnemonic PSA can be used to guide relevant questions for the patient in the office. This is P for joint pain, qualify with S for stiffness—increased stiffness after a period of inactivity lasting over 20 to 30 minutes that improves with activity—and A for axial to ask about back pain that is qualified by the same stiffness as noted above. Also, S can also be for sausage digit referring to dactylitis, or S for swelling. If two of three qualities are positive, then this should prompt formal screening and/or referral. The use of the validated Psoriasis Epidemiology Screening Tool (PEST) questionnaire is an easy method that is patient-facing and low burden on the office and providers. Positive results (≥ 3/5) should prompt diagnostic work-up and/or referral to a rheumatologist as appropriate. 

For patients who present with PsO and PsA, what are our therapeutic options?
Dr Merola: We have a large number of highly effective and overall safe options for patients with PsO with PsA.  The presence of different “domains of disease” (eg, skin disease, entheseal, axial, etc) will drive the most appropriate use of classes of agents in a given patient, along with consideration of other comorbidities (eg, inflammatory bowel disease, cardiovascular disease). This includes patient preference (eg, oral vs injectable) in a shared-decision making process. In broad terms, systemic treatment options including the following classes of therapeutics for which PsA FDA approvals exist: anti-tumor necrosis factor, anti-IL-17, Janus kinase inhibitors, anti-IL-12/23, anti-IL-23,  phosphodiesterase 4 inhibition, and CTLA4-Ig.

Dr Kim: Risk of safety issues related to the drugs listed above should be discussed with patients upon making a treatment decision. While we have somewhat limited head-to-head comparisons of these immunomodulating drugs, ustekinumab appears to have a favorable risk profile. These risks are discussed in our recent paper looking at of hospitalized serious infections¹ in addition to our previous work looking at the risk of cardiovascular events and atrial fibrillation.²  

Are there any therapies in the pipeline or research initiatives regarding PsA that excite you?
Dr Merola: We are embarking on some work through the PPACMAN group that looks at prevention of PsA among at-risk patients with PsO. This includes looking at the use of combination therapy strategies at different points in the disease journey with the NPF alongside others moving toward remission and cure initiatives.  Some newer mechanisms of interest include the oral tyrosine-protine 2 inhibitor class, with positive data in both skin and joint disease. 

Is there anything else regarding PsA that dermatologists should know?
Dr Kim: If needed, early recognition for referral with the appropriate treatments is the key to improve the overall outcome of patients suffering from both PsO and PsA. Ensuring patients education and awareness is also crucial to improving the outcomes. 

References
1. Jin Y, Lee H, Lee MP, et al. Risk of hospitalized serious infection after initiating ustekinumab or other biologics for psoriasis or psoriatic arthritis. Arthritis Care Res (Hoboken). Published online May 10, 2021. doi:10.1002/acr.24630

2. Lee MP, Desai RJ, Jin Y, Brill G, Ogdie A, Kim SC. Association of ustekinumab vs TNF inhibitor therapy with risk of atrial fibrillation and cardiovascular events in patients with psoriasis or psoriatic arthritis. JAMA Dermatol. 2019;155(6):700-707. doi:10.1001/jamadermatol.2019.0001