Types of Psoriatic Arthritis

There are different types of psoriatic arthritis.  Classification varies, depending on the source:

  • Asymmetric Oligoarticular PsA affects fewer than four joints, and (unlike RA) does not affect the same joint on both sides of the body.  This type of PsA is generally considered mild due to the small number of joints affected.  “Mild” is a comparative word that does not necessarily take into account the impact of the disease on a person’s life.  Approximately 70% of people with psoriatic arthritis have this type.
  • Symmetric Polyarticular PsA affects four or more joints, and (like RA) can affect the same joint on both sides of the body.  This type of PsA is more severe since more joints are involved.  Approximately 25% of people with psoriatic arthritis have this type.
  • DIP Predominant affects mainly the distal interphalangeal joints of the fingers and toes.  Inflammation of the DIPs is a clue that the autoimmune disease involved is PsA instead of RA.  Approximately 5% of people with psoriatic arthritis have this type.
  • Arthritis Mutilans, aka chronic absorptive arthritis, affects fewer than 5% of PsA and RA patients.  This type is severe and causes deformity.
  • Enthesitis is inflammation of the tendon/ligament insertion sites (where tendons/ligaments attach to bone). Over time, fibrosis or calcification can occur.
  • Spondylitis includes inflammation of the cervical spine (neck) and sacral spine (lower back), as well as hands, feet, hips, knees, elbows, and other joints as in RA and symmetric PsA.
  • Dactylitis affects fingers and toes, and indicates swelling of the entire digit.  This is in contrast to RA, wherein joints will swell, but not entire fingers/toes.

ClASsification criteria for Psoriatic ARthritis (CASPAR) requires inflammatory articular disease, but not necessarily visible swelling or symmetry.  Spine pain, enthesitis, or tendonitis are sufficient.  If that criteria is met, then at least three points from the following five categories qualify a person for a diagnosis of psoriatic arthritis:

  1. Psoriasis — either
    1. current psoriatic skin or scalp disease diagnosed by a rheumatologist or dermatologist (2 points), or
    2. personal history of psoriasis (1 point), or
    3. 1st degree (parent, child, sibling) or 2nd degree (grandparent, grandchild, aunt, uncle, nieces, nephews, half-siblings) blood relative with psoriasis (1 point)
  2. Psoriatic nails (1 point)
  3. Negative RF blood test (1 point)
  4. Dactylitis (swollen “sausage” fingers/toes)– current or history (1 point)
  5. New bone formation near joints visible on x-ray (1 point)

2 thoughts on “Types of Psoriatic Arthritis

  1. Good to see you back writing Socks! Are you now DX’d with PSA? This is all very interesting personally given that I have symptoms of RA, AS, and maybe PSA. My grandmother had psoriasis and her brother severe AS. I have symmetrical presentation in every joint big and small, classic RA bone erosion in the PIP and MCP joints but not the DIPs, and a positive RF test. But also had uveitis and have enthesitis in almost every joint. No nail symptoms. My official DX is RA but this autoimmune stuff is very weird indeed.

    • Thanks, Andrew. No dx change yet. My rash has finally be diagnosed as a “psoriasiform rash” which derm says seems to be a cross of a few different types of psoriasis. In researching PsA, I thought of you with your blown Achilles tendon a few years ago.

      What I find interesting is that mtx can be used to treat psoriasis. It would make sense that people who have joint involvement prior to skin symptoms might actually never see the skin symptoms because they’re kept under control with mtx. My rheum says that a positive anti-CCP is unique to RA, so who knows what she’ll eventually decide I have.

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