Psoriasis is an autoimmune condition which affects the skin and joints. It is sometimes referred to as one of the spondyloarthritides (inflammatory arthritis that is seronegative for rheumatoid factor (and/or does not fit the criteria for diagnosis as RA)).


  • Psoriasis – umbrella term for the condition, but often used to describe the disease when only skin lesions are present. Affects 1-3% of the population
  • Psoriatic arthritis – describes the joint involvement of the condition

Skin changes

  • Inflammation and production of excess skin, causes characteristic erythematous lesions, with silvery ‘plaques’.
  • Plaques are common at the knees and elbows, but can occur anywhere
    • Unlike eczema, they tend to occur on extensor surfaces, and around pressure points.

Nail changes

  • Psoriatic nail dystrophy – particularly associated with psoriatic arthritis, and rarer in patients who suffer only skin changes.
  • The nails will often be discoloured (a yellow/brown patchy colour)
  • May also be onycholysis
  • May be ‘pitting’ – small (needle sixed) little pits in the nail surface
  • Subungal hyperkeratosis – where there is proliferation of the deeper keratine layers of the nail – causing the smooth nail surface to be raised, whilst a mesh of keratin grows underneath.
  • ridging

Psoriatic Arthritis

Epidemiology and Aetiology

  • Genetic component
    • Often a family history – which can aid the diagnosis
    • HLA-B27 – present in 50% of those with spinal signs
  • Cause basically unknown
  • Smoking and excessive alcohol intake may increase the risk of getting the condition
  • Often associated with:
    • Rheumatoid Arthritis
    • Spondyloarthritides

Clinical features

  • Can essentially present with any variation of arthritic symptoms!
    • Often indistinguishable from RA, but is seronegative, and in association with skin signs, should be considered a separate condition.
    • Usually an oligoarthritis (2-5 joints, usually asyymetrical), usually weight bearing joints.
  • Check for psoriatic skin lesions, may not be obvious, and patients themselves may not even know they have them. Check specifically the
    • Natal Clef
    • Scalp
    • Umbilicus
  • Check for nail changes
  • In a minority of cases, the arthritis presents before skin and nail changes. In which case, you may be able to identify typical features of spondyloarthritides:
    • Dactylitis – literally – sausage shaped digit – results from inflammation of the whole finger
    • Enthesopathy – involvement of the enthesis. Can include enthesitis.
  • Osteolysis – perhaps the most characteristic sign. As the bone in the fingers is lost, there may be telescoping of the fingers
  • Spinal involvement – typically at the sacrum


  • Synovial biopsy – not routinely performed, but will show pathological differences from rheumatic conditions, even when the disease closely resembles RA.
  • Radiographs – may show osteolysis, which appears as a ‘pencil-in-cup’


  • Essentially follows that of the condition of which features are most prominent…
  • Treat as if RA – if RA signs are prominent
    • Methotrexate and leflunomide are the DMARD’s of choice. Hydrochlorequine is avoided as it exacerbates skin disease
    • Evidence for the efficacy of DMARD’s in PsA is not very conclusive
    • Anti-TNF-α treatments have not been used for very long, but look very promising!
  • o  Treat as if AS – if AS signs are prominent


  • PsA patients score slightly worse on QOL scores than the general population:
    • 1.0 is average value for general population
    • 0.9 is Psa
    • 0.8 in RA
  • Slight increased mortality (1.6x normal risk)
    • Mainly due to increased risk of cardiovascular disease

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