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How to Treat – Psoriatic arthritis
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Figure 2. Sagittal MRI of ankle region:
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).
Source: Arthritis Research and Therapy 2006;
8:207. See: bit.ly/2yUxi9Q
Pathophysiology
THERE is a well-established poly-
genic inheritance, with a relatively
high risk of the disease in family
members.
Psoriasis and psoriatic arthri-
tis are associated with Class I
MHC alleles, with genetic poly-
morphisms in the gene encoding
interleukin-23 receptor (IL23R),
combined with variants in the
TNF expression leading to clinical
manifestations. 7
The importance of the TNF and
the interleukin-23-interleukin-17
pathways in pathogenesis have
become apparent in recent years,
leading to a number of new treat-
ments for the disorder. 8
Disorder of these pathways lead
to the skin disease, joint and ten-
don manifestations of psoriatic
arthritis, axial symptoms and
extra-articular
manifestations
including uveitis and inflamma-
tory bowel disease (see figure 3). 9
Skin
Entheses
IL37/IL23/TNIL37/IL23/TNF/IL17
Trauma
Achilles tendon
IL23
TNF
Bone marrow
↑TH1
Dendritic
cell
↑Type 17
Macrophage
IL23
Intestine
THE IMPORTANCE
OF THE TNF AND
THE INTERLEUKIN-
23-INTERLEUKIN-17
PATHWAYS IN
PATHOGENESIS HAVE
BECOME APPARENT
IN RECENT YEARS,
LEADING TO A NUMBER
OF NEW TREATMENTS.
Muscle
TNF
IL17
RANK-L
Microbial
dysbiosis
Osteoclast
IL23
Synovitis
Tendonitis
Bone erosion
Tendon
Figure 3. pathogenic
Pathogenic pathway
pathways
psoriatic
arthritis.
Figure1.
in in
psoriatic
arthritis.
Clinical features
THE most common joint mani-
festations of psoriatic arthritis are
outlined in box 1. Psoriatic arthritis
can be categorised according to joint
involvement pattern and frequency
(table 2).
As a member of the spondyloar-
thropathy group, psoriatic arthri-
tis shares common features with
other disorders in this group. Some
diseases within this group exhibit
predominantly
axial
skeleton
involvement with peripheral arthri-
tis (mostly large joint) occurring
in a proportion of sufferers. This
group is termed the axial spondy-
loarthropathy (AxSpa) group and
includes ankylosing spondylitis.
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| Australian Doctor | 15 December 2017
The
peripheral
spondyloar-
thropathritis group conditions
within the spectrum exhibit pri-
marily peripheral joint symptoms,
with axial involvement seen less fre-
quently. Psoriatic arthritis, reactive
arthritis and IBD-associated spon-
dyloarthropathy commonly mani-
fest with predominantly peripheral
symptoms with axial symptoms less
common. It is important to note
that manifestations may fluctuate
and different symptoms may occur
over prolonged time periods, sepa-
rated by months or years. 10 Table
1 lists the different features of the
spondyloarthropathies.
Table 1. Features of the spondyloarthropathies
Psoriatic
arthritis
Ankylosing
spondylitis
Reactive
arthritis
Inflammatory bowel
disease associated
Peak age of onset 30-50 18-30 25-40 25-40
Gender ratio M:F 1:1 3:1 3:1 2:1
Axial joints affected % 50 100 100 30
Peripheral joints affected % 95 30 90 30
Enthesitis Common Common Uncommon Uncommon
Dactylitis Common Absent Uncommon Uncommon
HLA B27 (%) 50 90 70 30
Extra-articular features
Anterior uveitis, also known as iri-
tis, is the most common association.
It occurs in 8% of patients with
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established psoriatic arthritis and
precedes the development of pso-
riatic arthritis by several years in
about 11% of patients. 13
There is a higher prevalence of
inflammatory bowel disease in
patients with psoriasis and psoriatic
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