Patterns of joint involvement in rheumatic diseases
Are you curious about the joint involvement pattern of the most important arthropathies
in adults?
In the last part of this series, we’ll be looking at monoarthritis, oligoarthritis,
and polyarthritis in adults.
Let’s start with monoarthritis.
One example is gout, which classically presents as an acute monoarthritis of the metatarsophalangeal
joint of the big toe.
It’s also termed podagra, the Greek word for ‘foot trap’.
A significant case of gout can also result in swelling of the forefoot.
It’s so painful that even contact between the toe and bed linen can cause pain.
Don’t even think about walking!
Another condition that occurs as frequently as gout is pseudogout.
Like gout, pseudogout is also caused by crystal deposition.
But unlike gout, uric acid crystals aren’t deposited in and around the joint rather calcium
pyrophosphate dihydrate, in short CPPD.
It comes as no surprise that pseudogout is also termed acute CPP crystal arthritis.
The condition can also result in acute attacks of joint pain and in such cases often presents
as acute monoarthritis of the knee.
The next condition we’d like to take a look at is septic arthritis.
Joint involvement is usually monoarticular, with bacteria infiltrating the joint.
This can develop, for example, as a result of an intra-articular injection or through
a contaminated prosthetic implant.
Accordingly, septic arthritis is usually monoarticular and occurs in large joints.
So, if you come across cases of acute monoarthritis, these three diagnoses should also be on the
top of the list: gout, pseudogout, and septic arthritis.
Now, let’s take a look at a few examples of oligoarthritis.
Before we get started, here’s a recap: Oligoarthritis is defined as the involvement of two to four
joints.
This especially applies to a group of arthritic disorders termed spondyloarthropathies.
The name spondyloarthropathies imply that these conditions can lead to spinal inflammation.
The prefix “spondyl-” means spine.
Let’s create an overview by looking at which conditions belong to the spondyloarthropathies.
On the one hand, there is axial spondyloarthritis, which affects the axial skeleton, whereas
peripheral spondyloarthritis affects the peripheral skeleton.
You’re already aware of a type of axial spondyloarthritis: ankylosing spondylitis.
An x-ray of the spine usually shows changes in the vertebral bodies.
Examples of peripheral spondyloarthropathies are enteropathic arthritis, reactive arthritis,
and psoriatic arthritis.
As previously mentioned, the spondyloarthropathies can be differentiated into two types based
on their pattern of joint involvement, an axial form, and a peripheral form.
Axial involvement mainly affects the iliosacral joint and the spine.
Spondyloarthritis with peripheral joint involvement is characteristic of asymmetric large joint
oligoarthritis.
Only a few large joints are affected, in which there is no symmetrical involvement.
For example, arthritis of the knee could be present on the one side, whereas the hip and
upper ankle are affected on the other side.
So, you’ve noticed that there are spondyloarthropathies without facet joint involvement, namely the
spine.
There are historical reasons behind this.
The first member of the group of spondyloarthropathies was axial spondyloarthritis, which gave rise
to the name spondyloarthropathies as a result of the spinal inflammation observed in the
condition.
Over time, other conditions were added, which share common characteristics that don’t
necessarily affect the spine.
In total, there are five important characteristics shared by the spondyloarthropathies:
Spondyloarthropathies show a strong genetic component and are associated with the presence
of the HLA-B27 gene.
From a clinical perspective, they don’t only lead to arthropathies, but also inflammation
of the entheses, the sites where tendons or ligaments insert into the bone, also termed
enthesitis.
Extra-articular manifestations of spondyloarthropathies are common and include inflammation of the
eye such as uveitis and skin alterations such as psoriasis.
These disorders are also termed seronegative spondyloarthropathies.
The term is used to describe the absence of certain antibodies such as rheumatoid factor
in these diseases.
Therefore, because of these five common characteristics, the diseases continue to be classified as
spondyloarthropathies.
However, as we’ll see in the next slide, there are specific differences between these
spondyloarthropathies.
Let’s start with axial spondyloarthritis.
It’s characterized by axial involvement, with bilateral involvement of the iliosacral
joint and the spine.
Now, let’s take a look at the pattern of joint involvement of enteropathic arthritis,
which occurs together with chronic inflammatory diseases such as Crohn disease.
In contrast to axial spondyloarthritis, enteropathic arthritis manifests with peripheral joint
involvement.
There’s usually asymmetric oligoarthritis involving the large joints of the lower extremities.
So, if a patient presents with this type of asymmetric oligoarthritis, there is a chance
that the patient has chronic inflammatory bowel disease.
A condition with a similar pattern of joint involvement to enteropathic arthritis is reactive
arthritis.
It often occurs after bacterial infection of the gastrointestinal tract or the urethra.
The most common pattern observed is also asymmetric oligoarthritis of the lower extremities.
The patient should be asked whether there’s a recent history of infection in the 6 weeks
before joint pain onset.
If that’s the case, the diagnosis of reactive arthritis should be considered after excluding
other possible causes.
In addition, the course of the disease often provides you with a hint: Joint pain associated
with reactive arthritis eventually disappears and is rarely chronic.
The last spondyloarthropathy that we’d like to discuss is psoriatic arthritis.
Peripheral joint involvement is also a common feature of psoriatic arthritis.
However, one of the special characteristics of this condition in contrast to enteropathic
and reactive arthritis is that the smaller joints are usually involved, mainly affecting
the hand.
Therefore, psoriatic arthritis represents a special spondyloarthropathy.
In psoriatic arthritis, joint distribution usually appears as a ray pattern, affecting
all the joints of the digit.
The wrist is also usually affected.
Let’s look at it from a somewhat different perspective, which may help us to remember
it more easily: The pattern of joint involvement appears as if the hand has been shot through
by an arrow.
In addition to arthritis of the joints of the fingers, there’s also pronounced soft
tissue swelling.
Because more than five joints are usually affected and the degree of severity differs
on both sides of the body, this pattern of joint involvement is also classified as asymmetric
polyarthritis.
The second pattern of joint involvement in psoriatic arthritis is swelling of the DIP
joints, as shown in the image on the right, which is characteristic of transverse joint
involvement.
This pattern of involvement is quite interesting as the DIP joints usually remain unaffected
in other arthropathies.
One differential diagnosis of isolated DIP joint involvement is osteoarthritis.
Both of these patterns of joint involvement are only two of several possibilities.
For example, there’s a classification criterion by Moll and Wright, which differentiates between
five types.
But without going into too much detail, here are the most important characteristics to
remember: psoriatic arthritis is an asymmetric or symmetric polyarthritis of the digits in
a ray pattern or transverse involvement of the DIP joints.
In psoriasis, arthritis usually begins after skin involvement, with the diagnosis usually
known in many cases.
We previously mentioned that enteropathic arthritis, reactive arthritis, and psoriatic
arthritis belong to the spondyloarthropathies.
Therefore, in individual cases, an axial pattern of involvement may be observed.
If that’s the case, then it’s most likely unilateral involvement of the iliosacral joint
and less likely bilateral involvement, as observed in axial spondyloarthritis.
OK.
Now we’d like to move on to polyarthritis.
A classic example is rheumatoid arthritis.
It’s a symmetric polyarthritis that mainly affects the smaller joints, namely those of
the feet and hands.
The first joints to be affected are usually those of the feet, with wrist and MCP joint
involvement occurring at a later stage.
In addition to these joints, the PIP joints, and the MCP joint and interphalangeal joint
of the thumb can also be affected.
In contrast, there are joints that are usually unaffected by rheumatoid arthritis.
These include the DIP joints and the carpometacarpal joint.
Pain in these joints most likely indicates osteoarthritis, or in rare cases a different
type of arthritis.
As mentioned at the beginning, the aim of this episode is to compare the characteristic
patterns of joint involvement and not to present all of the joints that may be affected.
If you’d like a more detailed look at which joints play a role in the disease activity
of rheumatoid arthritis, check out the DAS28 score.
DAS stands for ‘disease activity score’.
The 28 joints are examined in the assessment, which measures disease activity in rheumatoid
arthritis.
However, the characteristic pattern in rheumatoid arthritis is best remembered as a symmetric
polyarthritis of the smaller joints.
The most commonly affected joints are the wrist, MCP and PIP joints, and the joints
of the toes.
Involvement of more than five joints can also occur in systemic lupus erythematosus, in
short SLE, an autoimmune disease with a highly variable clinical presentation.
Joint involvement is a common symptom: The initial clinical presentation in approximately
90% of patients with SLE is joint pain.
In SLE, arthritis presents as a symmetric polyarthritis of the smaller joints, especially
the MCP and PIP joints of the hand.
The DIP joints are also occasionally involved, and if so, it usually occurs in association
with the MCP and PIP joints and isn’t isolated as in psoriatic arthritis.
Therefore, the pattern of joint involvement in SLE resembles that of rheumatoid arthritis.
In addition, since both conditions frequently affect young women, an initial differential
diagnosis can be somewhat difficult.
In SLE, the feet are less likely to be affected than in rheumatoid arthritis.
Yet, the pattern of joint involvement is insufficient for a precise differential diagnosis.
Other tests are necessary such as serological tests and x-rays.
To sum up the pattern, SLE usually presents as symmetric polyarthritis of the smaller
joints of the hand that can also involve the DIP joints.