Spot the PsA
What skin condition is most strongly associated with psoriatic arthritis?
Psoriasis
Why: PsA occurs in around 1 in 5 people with psoriasis. Skin disease may precede, coincide with, or follow the arthritis.
A 70-year-old has chronic knee pain, worse after activity, with brief morning stiffness and no swelling. PsA, OA or inflammatory arthritis?
Osteoarthritis
Why: Mechanical pain, activity-related symptoms and short morning stiffness point towards OA rather than inflammatory arthritis.
Is there a single blood test that confirms a diagnosis of PsA?
No
Why: PsA is primarily a clinical diagnosis. Blood tests help assess inflammation and exclude alternative diagnoses but there is no diagnostic biomarker.
Which specialty should a patient with suspected PsA generally be referred to?
Rheumatology
Why: Early specialist assessment and treatment are important because uncontrolled PsA can cause irreversible joint damage and disability.
What is the term for diffuse swelling of an entire finger or toe, often described as a “sausage digit”?
Dactylitis
Why: Dactylitis is inflammation involving the whole digit, including joints, tendon sheaths and soft tissues. It is a characteristic feature of PsA.
A patient develops an acutely painful, red and swollen first MTP joint. Which diagnosis should be high on the differential?
Gout
Why: Acute monoarthritis of the first MTP = podagra, a classic presentation of gout. Always consider septic arthritis in an acutely hot swollen joint too.
Which two inflammatory markers may be raised in active PsA?
CRP and ESR
Why: Both can reflect systemic inflammation, although they can also be normal in PsA — normal inflammatory markers do not exclude the diagnosis.
What type of drug is methotrexate, commonly used as a conventional DMARD in PsA?
Conventional synthetic DMARD (csDMARD)
Why: Methotrexate is commonly used for peripheral joint disease, particularly when there is significant synovitis. It does not work well for axial disease.
What is inflammation where a tendon or ligament attaches to bone called?
Enthesitis
Why: Enthesitis is a hallmark of the spondyloarthropathies, including PsA. Common sites include the Achilles tendon and plantar fascia.
Which finding favours PsA over rheumatoid arthritis: DIP involvement or symmetrical MCP involvement?
DIP involvement
Why: DIP arthritis is characteristic of PsA and unusual in RA. Symmetrical MCP/PIP polyarthritis is much more typical of RA.
What is the typical rheumatoid factor result in PsA?
Negative
Why: Most patients with PsA are RF negative. RF positivity makes RA a consideration but does not exclude PsA.
Name one NSAID that could be used to help manage inflammatory musculoskeletal symptoms in PsA.
NSAIDs provide symptomatic relief from pain and inflammation but do not prevent long-term joint damage, so they aren't a substitute for disease-modifying treatment.
Name two nail changes associated with psoriatic arthritis.
Nail pitting and onycholysis
Why: Nail disease is strongly associated with PsA, particularly when the DIP joints are involved. Other changes include subungual hyperkeratosis and “oil-drop” discolouration.
A patient has psoriasis, inflammatory arthritis and a positive rheumatoid factor. Does a positive RF exclude PsA?
No
Why: RF is usually negative in PsA, but a positive RF does not rule it out. Diagnosis is based on the overall clinical picture.
What classification criteria are commonly used for psoriatic arthritis?
CASPAR criteria
Why: CASPAR = Classification Criteria for Psoriatic Arthritis. They use features including psoriasis, nail dystrophy, dactylitis, negative RF and radiographic new bone formation.
A patient has active PsA despite conventional DMARD treatment. What class of treatment might rheumatology consider next?
A biologic DMARD or targeted synthetic DMARD
Why: If disease remains active despite conventional treatment, treatment can be escalated to targeted therapies such as TNF inhibitors, IL-17 inhibitors or IL-23 pathway inhibitors, depending on the clinical phenotype.
Which pattern of peripheral joint involvement is particularly characteristic of PsA compared with RA?
Asymmetric oligoarthritis
Why: PsA has several patterns, but asymmetric oligoarthritis is classic. It can also cause symmetrical polyarthritis, DIP-predominant disease, arthritis mutilans and axial disease.
A patient with psoriasis develops inflammatory back pain. What type of PsA involvement should you consider?
Axial PsA
Why: PsA can affect the axial skeleton and cause a spondyloarthritis-type presentation. Think inflammatory back pain, sacroiliitis and/or spinal involvement.
What characteristic X-ray finding gives PsA its classic “pencil-in-cup” appearance?
Erosion with adjacent bony proliferation
Why: Erosion causes tapering of one bone end (“pencil”) with expansion/proliferation of the opposing bone (“cup”). It's a classic, although not always present, radiographic feature of PsA.
Why is it important to treat PsA early and effectively rather than simply managing the patient's pain?
To control inflammation and prevent irreversible joint damage and disability.
Why: PsA can cause structural joint damage and functional impairment. Early disease control improves long-term outcomes.