Psoriasis Australia

Primary Patterns of Psoriatic Arthritis (PsA)

Psoriatic arthritis (PsA) manifests in various forms, with each pattern affecting different joints and areas of the body.

Psoriatic arthritis (PsA) manifests in various forms, with each pattern affecting different joints and areas of the body. Understanding these patterns is crucial for accurate diagnosis and treatment. Below is a description of the five primary patterns of PsA:

1. Oligoarticular Psoriatic Arthritis

Oligoarticular PsA is the most common form of psoriatic arthritis, affecting around 70% of those diagnosed with the condition. It involves four or fewer joints, typically large joints like the knees, ankles, or wrists. Key characteristics of this pattern include:

  • Asymmetrical involvement: Unlike rheumatoid arthritis, which tends to affect joints on both sides of the body symmetrically, oligoarticular PsA often affects joints asymmetrically. For example, it may impact only the left knee and right ankle.
  • Joint pain and swelling: Patients may experience intermittent periods of joint swelling and pain, with the intensity varying from mild to severe.
    While oligoarticular PsA can sometimes appear milder due to the limited number of joints affected, without timely treatment, it can still lead to significant joint damage over time.

2. Polyarticular Psoriatic Arthritis

Polyarticular PsA, also known as symmetric PsA, is more similar to rheumatoid arthritis and involves five or more joints. It commonly affects smaller joints in the hands and feet but can also affect larger joints like the knees, hips, and elbows. Key features include:

  • Symmetrical involvement: Joints on both sides of the body are affected in a similar pattern. For example, both hands or both knees may be involved.
  • Resemblance to rheumatoid arthritis: Polyarticular PsA can be difficult to distinguish from rheumatoid arthritis due to similar patterns of joint involvement and inflammation.
  • Increased risk of joint damage: This form is more aggressive than oligoarticular PsA, with a higher likelihood of leading to permanent joint damage if not properly managed.

    Patients with polyarticular PsA often require systemic treatments, such as DMARDs or biologics, to control disease progression and inflammation.

3. Distal Interphalangeal Predominant Psoriatic Arthritis

Distal interphalangeal (DIP) predominant PsA primarily affects the small joints at the ends of the fingers and toes, closest to the nails. This form is relatively uncommon but distinctive due to its specific joint involvement. Key features include:

  • Nail changes: Patients with DIP PsA frequently experience psoriatic nail changes, such as pitting (small depressions in the nail), onycholysis (nail separation from the nail bed), or thickening.
  • Localized joint inflammation: Swelling and pain occur in the distal joints of the fingers and toes, often accompanied by stiffness and reduced range of motion.

    This pattern of PsA can be mistaken for osteoarthritis, which also commonly affects the DIP joints. However, nail involvement and other PsA-related symptoms can help distinguish the two conditions.

4. Spondylitis Psoriatic Arthritis

Spondylitis PsA primarily affects the spine and sacroiliac joints, causing inflammation in the vertebrae (bones of the spine) and the joints connecting the pelvis to the spine. This form can lead to severe back pain, stiffness, and reduced mobility. Key features include:

  • Spinal pain and stiffness: Spondylitis PsA often leads to stiffness in the lower back, neck, or sacroiliac joints, which may worsen after periods of rest, such as in the morning.
  • Reduced flexibility: In advanced cases, the inflammation may cause the spine to fuse, limiting movement and flexibility.
  • Inflammation of the entheses: Enthesitis, or inflammation where tendons and ligaments attach to bone, is common in spondylitis PsA, contributing to pain in the heel, knee, or other sites.

Because this form of PsA can resemble ankylosing spondylitis (another inflammatory condition affecting the spine), careful diagnostic evaluation is essential. Imaging techniques such as X-rays or MRIs are often used to confirm the diagnosis.

5. Arthritis Mutilans

Arthritis mutilans is the most severe and rarest form of psoriatic arthritis, occurring in less than 5% of patients. It is characterized by extreme joint damage and deformity, primarily affecting the hands and feet. Key features include:

  • Joint destruction: Arthritis mutilans leads to the destruction of bone and soft tissues, causing joints to collapse and fingers or toes to shorten or become deformed.
  • “Opera-glass hand”: This term refers to the telescoping appearance of the fingers when the bones are severely damaged, giving them a shortened, telescoped look.
  • Severe functional limitations: This form of PsA severely affects the patient’s ability to perform daily tasks due to the extensive joint damage and deformity.

    While arthritis mutilans is rare, early diagnosis and aggressive treatment are critical to prevent its progression. Biologics or advanced therapies are typically required to manage this form of PsA.

Importance of Early Diagnosis and Treatment

Understanding the different patterns of PsA is essential for accurate diagnosis and treatment. Early intervention is crucial for preventing long-term joint damage and maintaining a good quality of life. In Australia, various treatment options are available, including traditional DMARDs, biologics, and targeted synthetic DMARDs, to manage symptoms and prevent disease progression.

By identifying the specific pattern of PsA a patient has, rheumatologists can develop a more tailored treatment plan to address the individual’s unique symptoms and needs.