Psoriatic arthritis

Question 1

What is the etiology of arthritis?

Answer 1

Arthritis arises in 10-40% of psoriasis

• PsA MOST COMMONLY occurs AFTER onset of psoriasis
• 20% of PsA Patients dev PsA BEFORE onset of psoriasis: ie psoriatic arthritis sine psoriasis

Risk factors: metabolic syndrome (closely linked), Indian (also increased risk for sarcoidosis)

Question 2

How does psoriasis present as a skin condition?

Answer 2

Rash – erythematous, raised salmon-pink plaques with silvery scales; Psora = itch

-Common a/w Dandruff

Question 3

What is the CASPAR criteria for PsA?

Answer 3

> 3 points from the following:

1) Current psoriasis (scores 2 points)
2) Personal history of psoriasis (if current psoriasis is absent)
3) Family history of psoriasis (if personal history of psoriasis or current psoriasis absent)
4) Psoriatic nail dystrophy
5) A negative test for rheumatoid factor
6) Current dactylitis
7) History of dactylitis (if current dactylitis absent)
8) Radiological evidence of juxta-articular new bone formation.

Question 4

What are the clinical features suggestive of PsA sine psoriasis?

Answer 4

• Distal joint involvement (DIP Arthritis)
• Asymmetric distribution
• Presence of nail lesions (eg, pitting or onycholysis) or hidden psoriatic plaques (eg, in the scalp, gluteal fold, or umbilicus)
• HLA-C*06 (not commonly used in routine clinical practice)
• Dactylitis –circumference of swollen digit is >10% that of normal C/L digit
• FHx of psoriasis

Question 5

What are the X ray features of psoriatic arteritis?

Answer 5

• Central erosions (vs juxta-articular in RA): ‘pencil in a cup’ appearance
• Osteolysis: the bone/digit is essentially disappearing
• Ankylosis
• If there is marked erosions may lead to mutilans

Question 6

What are the 5 clinical patterns of psoriatic arteritis?

Answer 6

1) (OA-like) DIPJ arthritis
- Often with adjacent nail dystrophy, due to enthesitis extending into nail root
- **Dactylitis is characteristic:
causing fusiform swelling of entire digit

2) Asymmetrical Oligoarthritis (most common pattern in PsA)

3) (RA-like) symmetrical polyarthritis (may be indistinguishable from RA)
- Often begins w asymmetrical pattern
- Ddx from RA: Involvement of DIPJ, asymmetrical distribution of joint disease, SpA, sausage digits, new bone formation on XR, cutaneous findings, characteristic nail manifestations of PsA
- Good response to DMARDs

4) (AS-like) Spondylitis
- Presents with predominant U/L or B/L Sacro-Iliitis and Spondylitis -> pain/stiffness in lower back / buttock
- Pain on Gaenslen’s or Faber test!
- Only 50% are HLA-B27 +ve
- Poor response to DMARDs -> use NSAIDs or TNF-a

5) Arthritis mutilans (rare; 3%): severe deforming and destructive arthritis
- Marked periarticular osteolysis and bone shortening (‘telescopic’ fingers)
- Bilateral and Deforming + Loss of bony architecture

Some patient presents with >1 pattern; And pattern may change over time

• Arthritis Mutilans and DIPJ Arthritis – most SPECIFIC for PsA
• Because clinical patterns described above can change over time, the clinical manifestation is most commonly described using SPADE clinical domains

Question 7

What does the mnemonic SPADE (to describe clinical domains of psoriasis)?

Answer 7

1) S: Skin and nail disease (may be mild, and minority may develop AFTER arthritis)
- Skin: Erythematous, salmon-pink plaques with silvery scales typically found on hairline,
- **scalp (MUST ASK ABOUT DANDRUFF), peri-umbilicus, sacrum, extensor areas of elbows & knees

Nail changes (80-90%): PSORI

• Pitting: caused by shedding of nail plate cells
• Subungal plaque creating pathognomic oil spot Sign
• Onycholysis and dystrophy: separation of nail from nail bed
• Ridging (longitudinal ridges)
• Increased thickness (subungal hyperkeratosis)
• Note: nail changes seldom occur without skin changes

2) P - Peripheral arthritis
3) A - Axial disease
4) D - Dactylitis 2’ joint and tendon swelling (sausage finger / toe)
5) E - Enthesitis -> heel and sole pain (for plantar fasciitis and Achilles tendonitis)

Question 8

How is psoriasis arthritis managed?

Answer 8

Enquire for features of instability eg enlarging of existing plaques, new plaques, Koebner phenomenon

Treatment is based on DOMAINS of presentation

• Skin changes: topical steroids, phototherapy etc. Phototherapy involves exposing the skin to controlled levels of UV B light. Can promote skin growth and healing
• Oligo type: intra-art steroids, NSAIDs
• RA type: DMARDs effective (except hydroxycloroquine)
• AS type: NSAIDs, biologics, esp INF-Alpha Inhibitor (DMARDs ineffective)
• For Pain relief: NSAIDs +- analgesic (but may worsen skin lesions)