Psoriatic arthritis: Radiology and diagnosis
Psoriatic arthritis (PsA) is a chronic condition that can worsen over time if a person does not receive treatment. Without treatment, it can lead to permanent damage in the joints and tissues.
Around 85% of people with PsA receive a diagnosis before the age of 40.
Imaging tests can help ensure an early diagnosis. Early diagnosis and treatment are key to preventing PsA from worsening rapidly.
Types of radiology for PsA
X-rays can help diagnose and monitor psoriatic arthritis.
If a doctor suspects PsA, a number of options can help confirm the diagnosis.
Each test reveals different aspects of the disease. They may help identify:
- how far the disease has progressed
- what type of damage has occurred
- the best course of treatment
Radiography — usually an X-ray — is the traditional way to assess and keep track of PsA.
The advantage of an X-ray is that it is economical.
However, in its early stages, PsA involves soft tissue inflammation rather than bone and joint damage. Experts note that an X-ray may not show the early signs of PsA, as there may be no visible changes to bones.
As PsA advances, an X-ray can show that bones are becoming damaged and changing shape. In the later stages, the affected bones — particularly in the hands — may appear to have bent.
If someone has a personal or family history of psoriasis, but an X-ray shows no signs of PsA, a doctor may recommend other forms of imaging to confirm the diagnosis.
An MRI scan can provide a detailed image of soft and hard tissues.
A doctor may use this imaging test to check for problems with the tendons and ligaments, especially in the lower back and feet.
An MRI scan is more likely than an X-ray to pick up earlier signs of PsA.
Doctors can now use ultrasounds to detect changes in the bones and tissues of people with PsA.
An ultrasound can reveal signs of arthritis in people with skin psoriasis even before the arthritis symptoms become apparent.
Before diagnosing PsA, doctors need to rule out other forms of arthritis as the cause of joint pain and swelling.
Visual examinations, laboratory tests, and reviewing the person's medical history and family autoimmune history can help with this.
Laboratory tests for PsA include rheumatoid factor and anti-cyclic citrullinated peptide tests, which indicate the presence of certain antibodies.
These blood tests help rule out RA, gout, and osteoarthritis. A doctor considers these results with those of imaging.
No laboratory test can definitively identify PsA, but if tests show that certain antibodies are present, it may help indicate that the person has the disease.
Swollen fingers can be a sign of PsA.
A visual examination is one of the first steps toward a PsA diagnosis.
Several visual signs can help a doctor decide whether a person has PsA or another form of arthritis. Some include:
- skin lesions that are consistent with psoriasis
- color changes in the fingernails or toenails
- swollen fingers
A doctor can also use visual signs to differentiate PsA from RA. For example, RA symptoms tend to appear symmetrically, affecting the same joints on both sides of the body. This is not usually the case for PsA.
However, a doctor cannot use a visual examination to rule out other forms of arthritis. They will use imaging to support any diagnosis.
Who needs a test?
PsA can affect anyone. It develops most frequently in young adults, but it can appear at any age.
People with psoriasis or a family history of psoriasis are more likely to develop PsA and should be aware of the symptoms.
If someone develops arthritis symptoms and has either psoriasis or a family history of it, they should ask a doctor whether their symptoms could result from PsA or another autoimmune inflammatory disorder.
There is currently no cure for PsA. But current guidelines recommend prescribing a biologic drug — specifically a tumor necrosis factor inhibitor — for most people with a new PsA diagnosis, when the disease is in an early stage.
Examples of these biologic drugs include:
- adalimumab (Humira)
- etanercept (Enbrel)
- infliximab (Remicade)
- golimumab (Simponi)
- certolizumab pegol (Cimzia)
These drugs target specific parts of the immune system. They can help reduce the risk of symptoms becoming more severe. They may also slow the progression of the disease.
However, they may not be suitable for everyone. A doctor will work with the individual to determine the most appropriate course of treatment.
The guidelines also recommend avoiding or quitting smoking, managing weight, and getting regular exercise.
Other treatments can help reduce pain, swelling, and other symptoms.
Radiology and other testing can help with a PsA diagnosis. Getting an early diagnosis and starting treatment early increases the chance of slowing the progression of PsA.
Learn more here about the link between tumor necrosis factor and inflammatory diseases.
One of my parents and two of my siblings have psoriasis or psoriasis and PsA. Should I have a test, even though I have never had any symptoms?
No. There would be no reason to undergo testing without current or past symptoms to suggest inflammatory arthritis. Currently, there is no test that predicts PsA.
However, if nonspecific lower back pain has been present and there is a strong family history of psoriasis and PsA, imaging of the pelvis, specifically the sacroiliac joints, could reveal PsA as the cause of the nonspecific lower back pain.
If PsA is present, this would lead to a different treatment and management recommendation, compared with how lower back pain is managed.Nancy Carteron, MD, FACR Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.