Psoriatic arthritis

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Magnetic resonance images of the fingers in psoriatic arthritis. Shown are T1-weighted (a) pre-contrast and (b) post-contrast coronal images. Enhancement of the synovial membrane at the third and fourth proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints is seen, indicating active synovitis (inflammation of the synovial membrane; large arrows). There is joint space narrowing with bone proliferation at the third PIP joint and erosions are present at the fourth DIP joint (white circle). Extracapsular enhancement (small arrows) is seen medial to the third and fourth PIP joints, indicating probable enthesitis (inflammation of a tendon insertion).

Sagittal magnetic resonance images of the ankle region in psoriatic arthritis. (a) Short tau inversion recovery (STIR) image, showing high signal intensity at the Achilles tendon insertion (enthesitis, thick arrow) and in the synovium of the ankle joint (synovitis, long thin arrow). Bone marrow oedema is seen at the tendon insertion (short thin arrow). (b,c) T1 weighted images of a different section of the same patient, before (panel b) and after (panel c) intravenous contrast injection, confirm inflammation (large arrow) at the enthesis and reveal bone erosion at tendon insertion (short thin arrows).

Psoriatic arthritis (also arthritis psoriatica, arthropathic psoriasis or psoriatic arthropathy) is a type of inflammatory arthritis^{[1]:427-436[2]:194} that, according to the National Psoriasis Foundation, affects around 10-30% of people suffering from the chronic skin condition psoriasis.^[3] Psoriatic arthritis is said to be a seronegative spondyloarthropathy and therefore occurs more commonly in patients with tissue type HLA-B27. Treatment of psoriatic arthritis is similar to that of rheumatoid arthritis. More than 80% of patients with psoriatic arthritis will have psoriatic nail lesions characterised by pitting of the nails, or more extremely, loss of the nail itself (onycholysis).

Psoriatic arthritis can develop at any age, however on average it tends to appear about 10 years after the first signs of psoriasis. For the majority of people this is between the ages of 30 and 50, but it can also affect children. Men and women are equally affected by this condition. In about one in seven cases the arthritis symptoms may occur before any skin involvement.

[edit] Presentation

As well as causing joint inflammation, psoriatic arthritis can cause tendinitis and a sausage-like swelling of the digits known as dactylitis. Radiology will give the appearance of "fluffy, new" bone.

[edit] Causes

The exact causes are not yet known, but several genetic associations have been identified.^[4][5]

[edit] Types of psoriatic arthritis

There are five main types of psoriatic arthritis:

• Symmetric: This type accounts for around 50% of cases, and affects joints on both sides of the body simultaneously. This type is most similar to Rheumatoid arthritis and is disabling in around 50% of all cases.

• Asymmetric: This type affects around 35% of patients and is generally mild. This type does not occur in the same joints on both sides of the body and usually only involves less than 3 joints.

• Arthritis mutilans (M07.1): Affects less than 5% of patients and is a severe, deforming and destructive arthritis. This condition can progress over months or years causing severe joint damage.

• Spondylitis (M07.2): This type is characterised by stiffness of the spine or neck, but can also affect the hands and feet, in a similar fashion to symmetric arthritis.

• Distal interphalangeal predominant (M07.0): This type of psoriatic arthritis is found in about 5% of patients, and is characterised by inflammation and stiffness in the joints nearest to the ends of the fingers and toes. Nail changes are often marked.

[edit] Treatments

The underlying process in psoriatic arthritis is inflammation, therefore treatments are directed at reducing and controlling inflammation. NSAIDs such as diclofenac and naproxen are usually the first line medication.

Other treatment options for this disease include joint injections with corticosteroids - this is only practical if a few joints are affected.

If acceptable control is not achieved using NSAIDs or joint injections then second line treatments with immunosuppressants such as methotrexate or leflunomide are added to the treatment regimen. An advantage of immunosuppressive treatment is that it also treats the psoriasis in addition to the arthropathy.

Recently, a new class of therapeutics developed using recombinant DNA technology called Tumor necrosis factor-alpha inhibitors have come available, for example, infliximab, etanercept, and adalimumab. These are becoming increasingly commonly used but are usually reserved for the most severe cases. As more is learned regarding the long-term safety of these biologic agents there is a trend toward earlier use to prevent irreversible joint destruction.

[edit] Additional images

Magnetic resonance image of the index finger in psoriatic arthritis (mutilans form). Shown is a T2 weighted fat suppressed sagittal image. Focal increased signal (probable erosion) is seen at the base of the middle phalanx (long thin arrow). There is synovitis at the proximal interphalangeal joint (long thick arrow) plus increased signal in the overlying soft tissues indicating oedema (short thick arrow). There is also diffuse bone oedema (short thin arrows) involving the head of the proximal phalanx and extending distally down the shaft.

Magnetic resonance images of the fingers in psoriatic arthritis. Shown are T1 weighted axial (a) pre-contrast and (b) post-contrast images exhibiting dactylitis due to flexor tenosynovitis at the second finger with enhancement and thickening of the tendon sheath (large arrow). Synovitis is seen in the fourth proximal interphalangeal joint (small arrow).

(a) T1-weighted and (b) short tau inversion recovery (STIR) magnetic resonance images of lumbar and lower thoracic spine in psoriatic arthritis. Signs of active inflammation are seen at several levels (arrows). In particular, anterior spondylitis is seen at level L1/L2 and an inflammatory Andersson lesion at the upper vertebral endplate of L3.

Magnetic resonance images of sacroiliac joints. Shown are T1-weighted semi-coronal magnetic resonance images through the sacroiliac joints (a) before and (b) after intravenous contrast injection. Enhancement is seen at the right sacroiliac joint (arrow, left side of image), indicating active sacroiliitis.

[edit] References

[edit] External links

• National Psoriasis Foundation
• Psoriasis Cure Now nonprofit advocacy group
• The Psoriasis and Psoriatic Arthritis Alliance (PAPAA) - UK national charity