More than 30 years ago, Drs. Moll
and Wright described five clinical patterns of psoriatic
arthritis, in which they explained the specific joints
that were affected in different groups of patients:
End knuckles of the fingers and
toes (distal interphalangeal arthritis)
The small joints at the ends of the fingers and toes
are called distal interphalangeal joints (DIP). These
joints are so named because they are at the ends of
the fingers and toes (distal), and are the knuckles
between (inter) the small bones of the finger (phalangeal).
On the feet, the small joints are called metatarsal
phalangeal (MTP).
Nail changes are usually seen
when arthritis affects the end knuckles of the fingers
and toes. Nail changes can include pitting, lifting
and crumbling of the nail, and changes in color and
thickness of the nail plate.
Many similar joints on both sides
of the body (symmetrical polyarthritis)
This pattern may involve five or more joints (polyarthritis),
and similar joints on both sides of the body (symmetric).
This form of psoriatic arthritis may resemble a different
type of inflammatory arthritis known as rheumatoid arthritis.
One or only a few joints in an
asymmetrical pattern (mono or asymmetrical oligoarthritis)
Four or fewer joints are affected, usually in an asymmetrical
pattern. This is the most common form and occurs in
about 70 percent of all cases. For example, a large
joint such as a knee may be involved with one or two
small joints of the finger (DIP) or toe (MTP).
Spinal
Involvement
This pattern of psoriatic arthritis involves the spine.
The low back is most frequently affected.
Arthritis Mutilans
This is a severe form of psoriatic arthritis, which
can be extremely disabling. As the name suggests, this
form of arthritis can cause destruction and mutilation
(mutilans) of the small joints of the fingers and toes.
The fingers may appear swollen and sausage-like. Fortunately,
this is a rare form occurring in fewer than 1 percent
of all cases.
These patterns can help
in diagnoses when the arthritis first develops. Over
time, an increasing number of joints can become involved,
and the pattern of involvement could change.
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