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Clinical manifestations

The association between axial and peripheral attacks is frequent and favours greatly diagnosis. The sacroiliitis may be asymptomatic, purely and simply radiological. The attack of a distal interphalangeal joint combined with that of the corresponding fingernail is quite distinctive. The existence of a sausage-like toe or finger, in association with articular and synovial attack, is also highly characteristic.

A schematic distinction is made between peripheral and central attacks.

Peripheral attacks are most commonly cases of asymmetrical oligoarthritis affecting one or two large joints as well as a hand joint often combined with tenosynovitis. In 15 to 20% of cases, it may arise as a symmetrical polyarthritis resembling rheumatoid polyarthritis. However, besides the data sourced from the familial questioning and an in-depth skin examination, several characteristics differentiate psoriatic arthritis and rheumatoid arthritis: in psoriatic arthritis, articular attacks are less symmetrical, there is impact on the distal interphalangeal joints - rarely in isolation - there are no subcutaneous nodules, there is often at least some radiological impairment on the sacroiliac joint and the rheumatic serology is negative.

[|In peripheral psoriatic
arthritis, involvement of all joints of one or several fingers or toes should
be differentiated from involvement of several distal interphalangeal joints
(DIPs), the latter often being associated with nail psoriasis.|auteur195]

In 5% of cases we find ourselves confronted with arthritis mutilans, which develops very fast and constitutes a matter of true therapeutic emergency. It is most often observed in a young subject. Generally, it is associated with sacroiliitis and is mostly observed when the skin episode is severe, as well as in certain circumstances such as HIV psoriasis. It may lead to severe disability.

Axial attack is frequent and is encountered in 40% of psoriatic arthritis cases. In half of such cases it is associated with a peripheral attack. Isolated sacroiliitis is possible. This sacroiliitis is often less serious than that observed in ankylosing spondylarthritis. It is often asymmetrical or even unilateral in 30% of cases. It is clinically asymptomatic and visible solely by X-ray in half of cases. It is particularly observed in the male and it is associated with the HLA B27 group in 50 to 70% of cases. Spinal attack is often tardier in developing psoriatic arthritis than in the development of ankylosing spondylarthritis and tends to predominate in the cervicodorsal region.

In the case of pustular psoriasis, particularly the Zumbusch type, activated neutrophilic polynuclears may produce the equivalent of a SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis) and result in joint lysis.

It is also possible, albeit rarely, to observe aseptic osteomyelitis during psoriasis. This manifests itself in the form of muscle and bone pains not relieved by NSAIDs and is located around the long bones, the anterior thorax, the vertebrae and the mandibles.

Finally, it must not be forgotten that uric acid is increased in more than 30% of psoriatics and that gout is not rare.