PSORIASIS ARTHRITIS Flashcards
DEFINITION
Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy that can affect peripheral joints, the axial skeleton and the enthesis.
EPIDEMIOLOGY
Psoriatic arthritis: from epidemiologic studies that were preformed all over the world we can learn that arthritis among patients with skin manifestations ranges between 6-48%. The differences mainly stem from the different set of criteria used to define psoriatic arthritis in different studies.
Age
Peak of incidences is in the 4th decade. Not as young as patients of AS, but nevertheless young.
Can occur at any age - Children and elderly can be affected too
The main triggers include trauma and stress.
ETIOPATHOGENESIS
Genetic component- Compared to other rheumatic disease in which the most important genes belong to MHC class II, in PsA especially MHC class I genes are involved, in particular HLA-B and HLA-C alleles. HLA- Cw*0602 is the most frequent allele in psoriasis. Specifically, in psoriatic arthritis there is a strong association with HLA-b27, HLA-B27, HLA-B38 and HLA-B39.
Note that HLA-B27 is not as frequent as in ankylosing spondylitis, it is present in 50% of patient with the spondylitis (axial) form, and in 15% with involvement of the peripheral joints (similarly to the general population). We should remember that HLA-B27 is associated with the spinal inflammatory manifestation and not of the peripheral joints.
Enviromental component:
Trauma- in some patients affected by psoriasis the “deep Koebner phenomenon”
Vaccination (Rosolia)
Stress (i.e. moving house)
INFLAMMATION
Synovitis with T lymphocytes infiltration (CD4+ and CD8+), B cells and plasma cells, with a prevalence of T lymphocytes CD8+ in the synovial fluid and in the enthesis. There is also expression of pro-inflammatory cytokines: IL-1, interferon-γ, TNFα, IL-6, IL-12, IL-15, IL-17 and IL-18. The inflammation inside the joints (synovitis) in psoriatic arthritis has some differences from the one that is seen rheumatoid arthritis:
There is an increase vascularization
There is an increased infiltration of neutrophils and macrophages, but decreased DCs. Moreover, intracellular citrullinated proteins are not expressed.
inflammatory arthritis associated with psoriasis, which is usually negative for rheumatoid factor” and described five clinical patterns:
1)Asymmetric oligoarthritis – 13% of cases. In this case it should be easy to differentiate between rheumatoid arthritis which presents as symmetric polyarthritis and psoriatic arthritis that is Asymmetric oligoarthritic. Oligoarthritis 🡪 <5 joints; polyarthritis 🡪 >5 joints.
2)Symmetric polyarthritis – 63% of cases, defined as >50% of joints (grouping small joins of hands and feet) involved as matched pairs. This is the ‘rheumatoid arthritis-like form’, the most common (63%).
3)Predominant distal interphalangeal (DIP) joint involvement – <5% of cases. Defined as >50% of the total joint count were distal interphalangeal joints (fingers and toes included). Remember that in RA it is the proximal joint that is involved, the DIPs are rarely involved.
4)Predominant spondylarthritis – 5% of cases. Inflammatory spinal pain (in any of three areas— lumbar, thoracic and cervical), reduced spinal mobility with reference to normative values, and radiographic sacroiliitis (at least grade 2 unilateral sacroiliitis). A further category of isolated sacroiliitis was included.
5)Destructive (mutilans) arthritis
MOST COMMON?
The symmetric polyarthritis form is the most prevalent form (up to 70% of the cases). It is our role and challenge to differentiate it from RA. This is of particular challenge since the skin manifestation can occur AFTER the joint manifestations (even years later).
IS IT SEVERE?
Today we know that the disease could be as severe as RA, because bony erosions are seen in more than 60% of the patients! Moreover, 47% of the patients will develop the erosions within the first 2 years, and within 10 years 55% of the cases will develop ≥ 5 deformities. For this reason, treatment of this disease should be initiated as soon as possible.
The areas affected by the disease:
Skin (70% of cases) – this tells us that 30% of the patients DO NOT have skin manifestation. Skin manifestation is usually prior to joint involvement.
Tender swollen joints (universal)
Enthesis (25-50%)
Dactylitis (32-48%)
Nail disease (≈78%)
Axial involvement (25-70%)
How to differentiate RA to PA?
Involvement of the DIPs (distal phalanges) together with the PIPs (rarely as the only manifestation)
Oligoarticular forms (sometimes)
Spondylitis (50% of cases)
Dactylitis (50% of cases) (flexor tendon + synovitis).
Enthesitis (40% of cases) - especially in the Achilles tendon
Sacroiliitis (less symmetric than AS)
Anterior uveitis- occurs in up to 18% of the patients. It is more frequent in patients with exiial involvement and it occurs more bilaterally than uveitis occurring in AS (SpA are the most common diseases in patients affected by acute anterior uveitis).
Other manifestations – aortic valve insufficiency, pulmonary fibrosis.
Radiologically – erosions with periosteal reaction and ankylosis.
DIAGNOSIS
Radiological features of PsA include bone resorption or osteolysis, bone neoformation at enthesis level, sacroiliitis, often asymmetrical. Erosions are less frequent than in RA and the progression is slower.
X-ray, ultrasound and MRI to evaluate the presence of bone erosions and new bone formation and the level of the enthesis:
Mutilans arthritis
conditions seen in a child feet and in the hands and is due to a massive reabsorption of bone.
This is an example of the mutilans form, in a patient that suffers from both psoriatic arthritis AND scleroderma (or systemic sclerosis) 🡪 Raynaud phenomenon can be seen (discoloration of some parts of the skin). Important to remember that rheumatologic diseases can overlap.
DACTYLITIS
Frequently the involvement of the distal joint is associated with involvement of the nails and represents enthesitis that stretches from the nail toward the distal joint.
Dactylitis (sausage-like digits) is a very painful condition that can be refractory to treatment. It’s present in about 30% of patients as the first manifestation, and 48% of patieents will experience it during the follow-up.
DACTYLOMETER –> diameter of the finger.
IMAGING TECHNIQUES
X-ray – it can indentify osteolysis and new bone formation (image on the right). The erosions in the case of PA are bigger than the small erosions seen at the initial stages of Rheumatoid arthritis.
Ultrasound and MRI are more sensitive techniques able to detect synovitis, bone erosion, tendon involvement and enthesitis.
PATTERN —>joints of the hand is ‘pencil-in-cup’.
In order to be sure that you are seeing an X-ray of psoriatic patients
you should look for the presence of new bone formation (osteophytes) that is never seen in rheumatoid arthritis patients. In particular, the distant humeral joint sometime presents with a ‘fish tail’ sign that is never seen in RA patients.
NEW BONE FORMATION
OA OR PSORIATIC?
OA patients are usually elderly (60% of the elderly population!!!), and present with nodules due to bone formation and not inflammation (called Heberden’s and bouchard’s nodes).
