LOS ANGELES, California – If a patient with psoriasis has dactylitis, inflammatory back pain, and / or tendonitis, think about psoriatic arthritis until proven otherwise.
At the Society of Dermatology Physician Assistants’ annual fall meeting, Amanda Mixon, PA-C said psoriatic arthritis (PsA) affects 20 to 30% of people with psoriasis, “but I suspect the number is higher.” Mixon practices at the Colorado Center for Arthritis and Osteoporosis, Longmont, Colorado. Psoriasis usually precedes PsA 8 to 10 years, and PsA affects both sexes equally, usually by the fourth decade of life. Genetic and environmental factors play a role.
Clinically, 95% of patients with PsA show peripheral joint disease in the form of synovitis, tenosynovitis, dactylitis and / or enthesitis, often asymmetrically. “You can have small psoriasis and terrible arthritis, or vice versa,” Mixon said. “They don’t automatically correlate with each other. The only thing it does is nail psoriasis. That will correlate with dactylitis, which is basically an inflamed sausage-like finger or toe that happens for no apparent reason – a classic psoriatic arthritis finding, a slam dunk. It is important to refer these patients to a rheumatologist. “
She went on to say that 5% of PsA patients have axial involvement. “Always ask psoriasis patients if they have inflammatory back pain, as some of them are only axially affected,” advised Mixon. This is different from mechanical back pain caused by things like manual labor or excessive exercise, she noted. “Mechanical back pain gets better with rest. People with inflammatory back pain feel worst in the middle of the night and morning. The inflammatory proteins peak in the middle of the night, making you feel stiff when you wake up saying, ‘I feel like the tin man’; they have to do the work [kinks] out in the morning. It improves with exercise, but not with rest. “
Mixon said this is a sign that a patient might have PsA: “So when you see psoriasis patients ask, ‘How is your back? Does it wake you up in the middle of the night?'”
Since enthesitis is also common with PsA, Mixon makes it a point to ask psoriasis patients about tendon problems such as plantar fasciitis or tennis elbow. Inflammation of the distal interphalangeal joint (DIP) is another clinical sign. “Rheumatoid arthritis [RA] is a symmetrical disease, but that is not the case with PsA, “she said. So if a patient with a diagnosis of RA has DIP involvement,” it is not RA.
Patients with PsA can also have asymmetrical sacroiliac involvement. “They will complain of alternating gluteal pains that wake them up at night,” she said. “This is an important sign that something inflammatory is going on.”
The CASPAR (Psoriatic Arthritis Classification Criteria) criteria are often used to diagnose PsA, “but in rheumatology, people don’t fit in nice boxes, so there’s a lot of gray,” she said. To meet the criteria for PsA under CASPAR, patients must have inflammatory arthritis plus at least three points from the following categories: current skin psoriasis (2 points); History of psoriasis symptoms but no current symptoms (1 point); a family history of psoriasis and no current or past symptoms (1 point); Nail symptoms such as pitting, onycholysis or hyperkeratosis (1 point); a negative rheumatoid factor (1 point); and juxta-articular new bone formation in the X-ray image (1 point).
Therefore, a patient presenting with a swollen knee or finger and also suffering from psoriasis has nearly met the criteria for PsA, said Mixon, who co-founded Rheumatology Advanced Practice Providers (RhAPP), a national organization of medical assistants and nurses in the 2019, said Rheumatology. “Even a family history of psoriasis is a point.”
Common comorbidities associated with PsA are wide-ranging and include gastrointestinal disorders, steatosis, malignancies, obesity, metabolic syndrome, depression, anxiety, hypertension, cardiovascular disease, and uveitis. “The majority of the patients I see with PsA and psoriasis have comorbid depression,” she said. “They are often overweight and have cardiovascular disease. That is why it is so important to bring these people to treatment, because with the right treatment you can reduce this risk.”
Mixon announced that she is a member of the AbbVie, Lilly, Janssen and Amgen spokesperson’s office. She is also a consultant for Pfizer, Sanofi and Novartis.
Society of Dermatology Physician Assistants (SDPA) 19th Annual Fall Dermatology Conference. Presented on November 4, 2021.
Doug Brunk is a San Diego-based, award-winning reporter for MDedge and Medscape who began reporting on healthcare in 1991. He is the author of two books on the University of Kentucky Wildcats men’s basketball program.
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