Psoriatic Arthritis: A Dermatologist’s Perspective

This scientific presentation was given by Alice B. Gottlieb, MD, PhD, at a dinner program titled “HANDS ON Psoriatic Disease: A Live and Augmented Reality Experience for Advancing Patient Care Despite Modern Time Constraints,” which took place on March 1, 2019, at Renaissance Washington, DC Downtown Hotel. This program was independent and not part of the official 2019 American Academy of Dermatology Annual Meeting, as planned by its Scientific Assembly Committee.

Psoriatic arthritis is a major comorbidity of psoriasis¹ and occurs in about 30% of patients with psoriasis.² It can be oligoarticular or polyarticular. The condition can present as involving the distal interphalangeal joints, the joints nearest the fingernail. “Psoriatic arthritis is one of the seronegative spondyloarthropathies, and therefore, patients can have inflammatory low back pain that ultimately can lead to limitation of motion and permanent disability,” said Dr Gottlieb, clinical professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York.

Patients with psoriatic arthritis have enthesitis, inflammation where the ligaments, joint capsules, and tendons insert into bone. “The most specific site of psoriatic arthritis is the Achilles tendon. Other easily accessible sites are the medial and lateral epicondyles at the elbow,” said Dr Gottlieb. Psoriatic arthritis is also associated with diffuse swelling of the toes or the fingers. This is called dactylitis and is due to inflammation in all the structural components of the toes or fingers.

“The sine qua non for the radiographic features in psoriatic arthritis is finding both excess bone formation and destruction of bones in the same unit,” said Dr Gottlieb. The pathogenic pathways that result in the skin disorder in psoriasis and the joint damage in psoriatic arthritis can be overlapping or distinct. Tumor necrosis factor (TNF), IL-17A, and IL-23 are abundantly expressed within the cutaneous lesions and in the joints of patients with inflammatory psoriatic disease.^3,4

Compared with psoriasis, psoriatic arthritis has an even greater impact on quality of life, said Dr Gottlieb. Pain is the primary complaint of patients with psoriatic arthritis, followed by skin problems.

Nail changes may occur in up to 80% of patients with psoriatic arthritis.⁵ “I find this particular effect most useful when I have somebody with arthritis of the hands,” said Dr Gottlieb. “When I’m not quite sure whether it’s psoriatic arthritis, but the patient has nail changes, that clinches it.” If the patient has no nail changes and is not on a systemic treatment, then consider an x-ray, suggested Dr Gottlieb.

“It’s not surprising that the nail can be linked to psoriatic arthritis, especially if you have psoriatic arthritis in the distal interphalangeal joint, because the enthesis at that joint inserts right at the nail matrix, which is where growth of the nail starts,” said Dr Gottlieb. “Therefore, if you have inflammation where that tendon inserts, you will find that the information will spill over into the matrix and lead to the typical nail findings.”

While most patients with psoriatic arthritis experience skin lesions, the psoriasis can be easily missed if the patient’s skin, including intertriginous areas and the scalp, is not examined carefully. “Many psoriatic arthritis patients do not have a lot of skin involvement, but what they have they want to get rid of,” said Dr Gottlieb. “The patient wants to be clear of the skin manifestations and they want to have no joint pain or disability.”

The dermatologist plays a key role in the identification of early psoriatic arthritis. Psoriasis is one of the top predictors of who is at risk of developing psoriatic arthritis, but a diagnosis is not necessarily always clear-cut. “The patient is often unaware that their aches and pains have anything to do with their skin disease,” said Dr Gottlieb. “By asking a few questions and by looking especially for enthesitis, which can be the presenting sign of early psoriatic arthritis before a swollen joint, within a couple of minutes a dermatologist can make a diagnosis.” 

“Studies have shown that a delayed diagnosis of psoriatic arthritis can negatively impact long-term patient outcomes,” said Dr Gottlieb. Data show that even a 6-month delay in referring a patient to a rheumatologist who will appropriately treat their psoriatic arthritis makes the patient four times more likely to develop joint erosions, and doubles the risk of experiencing functional disability.⁵

“Having scalp lesions, nail dystrophy, intertriginous involvement, a family history of psoriatic arthritis, and having more body surface involved in psoriasis are factors that can increase your risk of psoriatic arthritis,” noted Dr Gottlieb. While the presence of these risk factors should cause concern, Dr Gottlieb warned that body surface area should not be used as a decision point on whether to ask about psoriatic arthritis. “You ask every patient with psoriasis about psoriatic arthritis,” she said. “If you don’t, you might give a topical steroid for psoriasis, and you will be doing the patient a disservice.” 

She pointed out that now that there are two classes of drugs available to treat psoriatic arthritis: IL-17A blockers and TNF blockers, which not only control signs and symptoms, but also inhibit radiographic progression. 

“When I find psoriatic arthritis,” said Dr Gottlieb, “I treat both the skin and joint disease, and the patient has a new life—not only do they look good, they feel better, they move better, they have more energy—that’s the most important message.”

Prolonged stiffness or immobility is a sign of inflammatory arthritis, said Dr Gottlieb. “People generally have more mobility as they move in the day, whereas somebody with noninflammatory arthritis is worse on activity.” A tender, red, swollen joint is an inflammatory sign in active psoriatic arthritis. Patients will complain of profound fatigue—a woman may describe this as feeling like the fatigue of early pregnancy.

The differential diagnosis of psoriatic arthritis is shown in the Table. There can be overlap among different inflammatory conditions. In a study of 94 patients with psoriasis who had musculoskeletal complaints evaluated in a tertiary care clinic by a team of dermatologists and rheumatologists, 41% had psoriatic arthritis, 27% had osteoarthritis, 15% had psoriatic arthritis and osteoarthritis, 13% were indeterminate, 2% had gout, 1% had psoriatic arthritis and gout, and 1% had osteoarthritis and gout.⁶

“The diagnosis of psoriatic arthritis is made clinically by and large,” said Dr Gottlieb. “You have to have an inflammatory musculoskeletal condition, which is either enthesitis, arthritis, or low back pain. For example, if you have nail findings, a psoriasis plaque, and an inflammatory musculoskeletal condition, by definition, you have psoriatic arthritis.”

In addition to talking with and examining a patient, said Dr Gottlieb, there are two freely available screening tools one can use. The first is called PSA, an acronym that stands for Pain in the joints, Stiffness that is prolonged—upon waking in the morning or after a period of inactivity of 30 minutes or more—and Swelling (sausage digit), and Axial spine involvement. The second is another acronym, PEST, for Psoriatic Epidemiology Screening Tool, and consists of five questions to ask patients. “If they answer yes to three of the five,” Dr Gottlieb said, “you should do rheumatologic evaluation.” PEST is available free from the National Psoriasis Foundation website (psoriasis.org/psoriatic arthritis-screening/providers) and the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis app. 

Psoriatic arthritis is a potentially disabling disease and a common comorbidity in patients with psoriasis.¹ Patients are often unaware that their musculoskeletal complaints could be related to psoriatic disease. “Being cognizant of the risk factors, looking for signs and symptoms, especially in patients who’ve had psoriasis for several years, and understanding the pathophysiology of psoriatic arthritis can help inform decisions on treatment options,” said Dr Gottlieb, especially those that can inhibit structural damage, control signs and symptoms, and help improve patient quality of life. She added that dermatologists are “in the unique position to be able to detect psoriatic arthritis early, and ensure that patients receive the care they deserve.”