Psoriatic arthritis is an inflammatory arthritis affecting the joints and
connective tissue and is associated with psoriasis of the skin or nails.
Psoriatic arthritis is a progressive disorder ranging from mild synovitis to
severe progressive erosive arthropathy. People with psoriatic arthritis
presenting with oligoarticular disease progress to polyarticular disease and a
large percentage develop joint lesions and deformities, which progress over
time.
The disease is autoimmune-mediated with defined HLA associations (HLA-B27,
-B17, -CW6, -DR4, -DR7 and others). Occasionally, it may occur in the absence of
skin disease, or there may only be an insignificant rash which may not be
noticed by the sufferer. Nail changes are a characteristic feature of the
illness. The inflammatory process may involve the synovium and intra-articular
structures, ligaments, fascial tissues and tendons
Risk factors
Psoriatic arthropathy is much more common in the western white population
than in other races.
Men are more commonly affected by the spondylitic subtype, with higher
incidence of the 'rheumatoid' pattern of disease among women.
It is most common in middle age (35-55) but may be seen in patients of any
age.
Differential diagnosis
Features that distinguish psoriatic arthritis from other forms of
inflammatory joint disease include the pattern of joint involvement (eg, DIP
joint involvement), the swelling of an entire digit (dactylitis), the presence
of enthesitis, and the absence of RF (or anti-citrullinated antibodies).
An important subgroup of patients with psoriatic arthritis suffers from
inflammatory spinal disease (spondylitis), which looks similar but is not
identical to ankylosing spondylitis. Other forms of arthritis that may be
difficult to distinguish from psoriatic arthritis include osteoarthritis and
gout.
