How Is Severity Determined?

Psoriatic arthritis (PsA) is considered a challenging disease to diagnose, in part because of its diverse set of symptoms that can vary from person to person.1 A chronic, systemic inflammatory condition, the joints involved in PsA can also vary over time.2 Skin symptoms of psoriasis typically appear before the joints become involved. Sometimes people may go 8-10 years before any joint symptoms are apparent. The severity of the disease is based on several factors:

  • Peripheral joint involvement
  • Pain, reported by the patient using a visual analog or category rating scale
  • Patient global assessment of disease activity
  • Physical function, as measured by the Health Assessment Questionnaire
  • Health-related quality of life (QoL), as assessed by a general measure or a PsA-specific measure (for example, the Psoriatic Arthritis QoL)
  • Fatigue, measured by the patient or using a general instrument such as the Functional Assessment of Chronic Illness Therapy
  • Laboratory tests measuring acute phase reactants, including C-reactive protein (CRP) or erthrocyte sedimentation rate (ESR)3

Additional considerations are enthesitis (inflammation at the attachment points of tendons and ligaments), dactylitis (swelling of the digits in a sausage-like formation), spine disease, nail disease, and structural status as determined by radiographic assessment, which may include ultrasound, MRI (magnetic resonance imaging) or CT (computed tomography).4

Progression of psoriatic arthritis

People with PsA may initially experience only stiffness and pain initially without any other symptoms.  This pain and stiffness may be intermittent, brief flare-ups of symptoms might appear to go away. Many people may think that their joint symptoms spontaneously have resolved.

PsA often begins in the distal joints, those farthest away from the core of the body, such as the joints in the fingers and toes. Musculoskeletal symptoms are often slow to develop and hidden. A rapid onset of PsA symptoms is also possible and is reported in about one-third of people with PsA.

PsA may initially appear as an oligoarticular or even a monarticular disease. “Oligo” means few, and “mon” means one. Oligoarticular PsA refers to less than or equal to four joints and is often asymmetric, occurring on only one side of the body with the opposite side unaffected. However, over time, many people gradually develop polyarticular and symmetric disease, with several joints affected on both sides of the body. “Poly” means many, and in the case of PsA, refers to more than four joints affected.2,4 With effective treatment, some people with polyarticular disease may become oligoarticular.2

Definition of mild, moderate, and severe psoriatic arthritis

Mild disease is generally characterized by oligoarticular PsA and has minimal impact on the person’s quality of life (QoL). Moderate disease shows an impact on the daily tasks of living and physical functions. Moderate disease may also impact the mental well-being of the person and shows a lack of response to mild treatment, such as with non-steroidal anti-inflammatory drugs (NSAIDs). Severe disease greatly impacts the person’s QoL. With severe disease, a person cannot perform major daily tasks of living without pain or dysfunction. There is a large impact on both physical and mental well-being.5

Arthritis mutilans

The most severe form of PsA is called arthritis mutilans. Approximately 5% of people with PsA have arthritis mutilans. Arthritis mutilans is characterized by digital shortening of the fingers or toes due to severe bone destruction. In arthritis mutilans, the bones in the fingers or toes degrade and begin telescoping into each other, sometimes referred to as a “pencil-in-cup” deformity, as it resembles a pencil in a cup on x-ray images. It may also be called “opera glass finger.” Arthritis mutilans is often associated with PsA that affects many joints throughout the body (polyarticular disease), as well as symmetrical distribution (on both sides of the body), inflammation between the spine and the pelvis (sacroiliitis), and long disease duration. Arthritis mutilans causes severe deformity and loss of function for the person with PsA.6

Severity impacts treatment recommendations

The severity of PsA determines the treatment approach. Mild disease that affects only peripheral joints may be treated with NSAIDs and/or intra-articular injections of corticosteroids. Injections of joints covered by psoriatic plaques must be performed with caution due to the abundance of bacteria usually discovered on the skin lesions.7

For moderate to severe PsA, treatments that target joint disease in PsA can reduce symptoms and prevent disease progression. Recommended treatments include disease-modifying anti-rheumatic drugs (known as DMARDs). The first step for treatments is usually DMARDs such as methotrexate, leflunomide, or sulfasalazine. Other treatments include medicines that target tumor necrosis factor (TNF), a cell-signaling protein that produces a wide range of inflammation in PsA. Examples of TNF blockers include etanercept (Enbrel), adalimumab (Humira), infliximab (Remicade), golimumab (Simponi), and certolizumab pegol (Cimzia). Other DMARDs that have proven effective in clinical trials include ustekinumab (Stelara), and secukinumab (Cosentyx).2 The FDA has also recently approved Inflectra (infliximab-dyyb), a biosimilar to infliximab, for the treatment of PsA.8

Severely impacted joints may also be referred for surgical care. Arthroscopic surgery to the synovial capsule has shown to be effective, and joint replacement or reconstructive surgery for hips and knees are occasionally necessary and have proven successful. However, high rates of recurrent joint damage have been noted after surgery for PsA, particularly in the hand.9

Written by: Emily Downward | Last reviewed: October 2016.
View References