Psoriatic Arthrits Quiz: Phenotypes

June 17, 2019

Rheumatology Network Staff

In this installment of our psoriatic arthritis quiz series, we focus on phenotypes unique to psoriatic arthritis. We also include a question or two on other issues that may stump you.

In this installment of our psoriatic arthritis quiz series, we focus on phenotypes unique to psoriatic arthritis. We also include a question or two on other issues that may stump you.

Psoriatic arthritis is a condition exclusive to adults.

A. True
B. False

Photo caption: (©MarilynBarbone,AdobeStock)

“Psoriatic arthritis can begin during childhood,” write Christopher T. Ritchlin, M.D., M.P.H., and colleagues in 2017 in the New England Journal of Medicine. “There are two clinical subtypes; they are not mutually exclusive. Oligoarticular psoriatic arthritis (characterized by four or fewer affected joints) has a peak onset at one to two years of age and occurs predominantly in girls. This form is associated with a positive test for antinuclear antibodies and chronic uveitis and is often characterized by dactylitis (diffuse swelling of a toe or finger). The second subtype (characterized by any number of affected joints) develops between 6-12 years old and is associated with HLA-B27; antinuclear antibodies are usually absent. This form has a one-to-one sex ratio, with dactylitis, enthesitis (inflammation at tendon, ligament, or joint-capsule insertions), nail pitting, onycholysis, and axial involvement occurring more frequently than in the first subtype. According to the International League of Associations for Rheumatology classification system, psoriatic arthritis is distinct from other forms of juvenile idiopathic arthritis and is defined by the coexistence of arthritis and psoriasis in the absence of features of other forms of juvenile idiopathic arthritis. A child with arthritis who does not have psoriasis but who has two or more features of psoriatic arthritis, such as dactylitis, nail pitting, onycholysis, or a family history of psoriasis (first-degree relative), meets the criteria for psoriatic arthritis.”

REFERENCE: Christopher T. Ritchlin, M.D., M.P.H., Robert A. Colbert, M.D., Ph.D., and Dafna D. Gladman, M.D. “Psoriatic arthritis.” New England Journal of Medicine. March 9, 2017. DOI: 10.1056/NEJMra1505557

Photo caption: (©MarilynBarbone,AdobeStock)

95 percent of patients with psoriatic arthritis test negative for rheumatoid factor or anti–cyclic citrullinated peptide antibodies. For 40 percent of patients, the levels of serum C-reactive protein or the erythrocyte sedimentation rate are elevated. And, approximately 25 percent of patients with psoriatic arthritis are HLA-B27 positive.

At what point should imaging be conducted?

A. During the first visit.
B. When a test result is positive.
C. Only if HLA-C*06 is positive.
D. Only if HLA-B27 is positive.

Photo caption: (©EdwardOlive,Shutterstock.com)

Imaging tests should be ordered when a test result is positive. This will aid in determining whether the patient has psoriatic arthritis, rheumatoid arthritis or other.

Of note, HLA-C*06 is a risk factor for psoriasis only, not for psoriatic arthritis. “In psoriatic arthritis, frequencies of HLA-B*08, B*27, B*38, and B*39 have been observed, with specific subtypes of those alleles linked to subphenotypes, including symmetric or asymmetric axial disease, enthesitis, dactylitis, and synovitis,” Ritchlin, et al. write in the New England Journal of Medicine.

REFERENCE: Christopher T. Ritchlin, M.D., M.P.H., Robert A. Colbert, M.D., Ph.D., and Dafna D. Gladman, M.D. “Psoriatic arthritis.”New England Journal of Medicine. March 9, 2017. DOI: 10.1056/NEJMra1505557

Photo caption: (©EdwardOlive,Shutterstock.com)

Which of the following are associated the five clinical subtypes associated with psoriatic arthritis?

A. Axial
B. Distal
C. Polyarticular
D. Oligoarticular
E. Other

Photo caption: (©Phenyx7776.Shutterstock.com)

The five clinical subtypes associated with psoriatic arthritis include:

1. Oligoarticular subtype which affects four or fewer affected joints. It usually occurs asymmetrically.
2. The polyarticular subtype affects five or more distal interphalangeal hand and/or feet joints, but it usually occurs with other subtypes affecting other joints appearing symmetrically. It is often mistaken for rheumatoid arthritis.
3. The distal subtype affects distal interphalangeal joints of the hands and/or feet. It usually occurs in concert with other subtypes, but it is rare, occurring alone in only 5 percent of patients.
4. Arthritis mutilans is a deforming and destructive subtype that involves marked bone resorption or osteolysis. It is characterized by telescoping and flail digits.
5. The axial or spondyloarthritis subtype primarily involves the spine and sacroiliac joints.

Photo caption: (©Phenyx7776.Shutterstock.com)

A patient visits his rheumatologist complaining of arthritic pain in his fingers which appear purplish. His nails are exhibiting signs of pitting. Palpation of his distal joints revealed soft swelling due to inflammation.

No other clinical testing has been conducted, but upon visual observation, what could be causing the discoloration and soft swelling?

A. Osteoarthritis
B. Psoriatic Arthritis
C. Rheumatoid Arthritis
D. Gout
E. SLE

Photo caption: (MedicalIllustrations.com, 01B0W1EW)

Even though distal joint involvement is associated with both psoriatic arthritis and osteoarthritis, soft swelling of distal joints with purplish discoloration is suggestive of a psoriatic arthritis diagnosis. In this case, osteoarthritis can probably be ruled out because in those cases, swelling arises from a bony osteophyte and is solid. Nail disease (pitting or onycholysis) is often associated with psoriatic arthritis, but not osteoarthritis.

In addition to osteoarthritis, psoriatic arthritis is distinctly different from rheumatoid arthritis, osteoarthritis, gout, pseudogout, systemic lupus erythematosus, and other forms of spondyloarthritis. It tends to be oligoarticular and less symmetric than rheumatoid arthritis, but over time it can become polyarticular and symmetric. Affected joints tend to be tender (more than in rheumatoid arthritis). And, more than 40 percent of patients with psoriatic arthritis have spinal involvement of the lumbar, thoracic or the cervical spine.

It can manifest as monoarthritis of the toes or as dactylitis. And, uric acid levels can be elevated. For these two reasons, psoriatic arthritis can often be misdiagnosed as gout or pseudogout.

REFERENCE:

Siba P.Raychaudhuri, Reason Wilken, Andrea C. Sukhov, Smriti K. Raychaudhuri, Emanual Maverakis."Management of psoriatic arthritis: Early diagnosis, monitoring of disease severity and cutting edge therapies." Journal of Autoimmunity. January 2017. https://doi.org/10.1016/j.jaut.2016.10.009

Photo caption: (MedicalIllustrations.com, 01B0W1EW)

A patient with a diagnosis of inflammatory arthritis presents to your clinic. What nail changes are not associated with psoriatic arthritis?

A. Onycholysis
B. Nail Pitting
C. Severe destructive changes
D. Hutchinson signs

Nail involvement is common in psoriatic arthritis. Specifically, onycholysis and nail pitting. Onycholysis is separation of the nail from its bed. Sharp demarcations in the nail is called nail pitting. Sometimes in psoriatic arthritis there is severe destructive changes of the nail as well. Huntchinson sign is the periungual spread of pigment and it is associated with melanoma.