What is psoriatic arthritis?

Psoriatic arthritis is a form of arthritis that affects some people with psoriasis. Psoriasis is a chronic skin and nail disease characterized by red, scaly rashes and thick, pitted fingernails. About one-third of children with psoriasis will have psoriatic arthritis.

Psoriatic arthritis is a form of juvenile idiopathic arthritis (JIA) and is characterized by chronic joint inflammation and swelling, as well as an increased risk for asymptomatic eye inflammation.

Psoriatic arthritis accounts for approximately 6 percent of all cases of juvenile arthritis.

Causes

Although the cause of psoriatic arthritis is unknown, factors such as immunity and the environment may play a role. Genetics also appear to be involved: 40-80 percent of children with psoriatic arthritis have an affected first- or second- degree family member, such as a sibling, parent, grandparent or aunt/uncle.

Signs and symptoms

The symptoms of psoriatic arthritis vary from child to child and range from mild to severe.
Psoriasis is just one symptom of psoriatic arthritis, and not all children with psoriatic arthritis have the psoriasis skin rash.

Children with psoriatic arthritis may have any of the following symptoms:

• Swelling of the small and large joints
• Inflammation where the tendons and ligaments attach to bone (enthesitis)
• Swelling of an entire finger or toe (dactylitis)
• Arthritis of the lower back (sacroiliitis)
• Arthritis of the spine (spondylitis)
• Inflammation of the eyes (uveitis)
• Morning stiffness
• Back pain or stiffness
• Pitting or peeling of the nails
• Red nail beds or cuticles

Young children with psoriatic arthritis are more likely to show symptoms in the small joints, have a positive ANA, experience finger or toe swelling, and are at increased risk of developing uveitis, a potentially serious eye condition.

Symptoms of psoriatic arthritis may resemble other medical conditions or problems. Always consult your child's doctor for a diagnosis.

Testing and diagnosis

At The Children’s Hospital of Philadelphia, rheumatologists diagnose psoriatic arthritis by:

• A physical examination of your child
• A complete family medical history
• A detailed list of symptoms
• Laboratory tests, including:
  • Complete blood count. This test allows for assessment of anemia, or low blood counts. Anemia can be secondary to chronic inflammation from the arthritis. This test also checks the white cell and platelet count. Platelets can be elevated when there is inflammation.
  • C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR or sed rate). These tests are done to determine if there is inflammation in the body. Children with psoriatic arthritis often have an elevated CRP and/or ESR at diagnosis or with continued disease activity.
  • ANA antibody. ANA is an antibody that is present in about 20 percent of normal, healthy people. Children with psoriatic arthritis who have a positive ANA have an increased risk of developing asymptomatic eye inflammation (uveitis). The frequency with which ophthalmology screening is recommended for your child will depend on whether this antibody is present or not.
• Imaging tests may be recommended, including:
  • X-ray. A diagnostic test that uses invisible electromagnetic energy beams to produce images of the joints onto film. These x-rays allow your physician to assess for damage to the joints.
  • Magnetic resonance imaging (MRI). A diagnostic test that does not involve radiation and allows your physician to assess for active/ongoing inflammation in the affected joints. MRI of the pelvis can be particularly helpful if your physician is concerned about arthritis of the lower back.
  • Ultrasound. This test can be done in the clinic by your rheumatologist to assess for inflammation of the joints and the tendon insertions. This test does not work well to assess for inflammation of the joints of the lower back or spine.

Treatment

The goal of treatment for psoriatic arthritis is to reduce pain and stiffness, prevent deformities, and help your child maintain as normal and active a lifestyle as possible.

Specific treatments for your child will be determined by his doctor based on:

• Your child's overall health and medical history
• Extent of the condition
• Your child's tolerance for specific medications, procedures, and therapies
• Expectation for the course of the disease
• Your opinion or preference

Some medications used to treat juvenile idiopathic arthritis are also used to treat psoriatic arthritis, including:

• Nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce pain and inflammation
• Injection of steroids directly into the affect joint(s)
• Disease-modifying anti-rheumatic drugs (DMARDS) such as methotrexate. These medications may also help the psoriasis rash.
• Biologic medications such as infliximab, adalimumab, or etanercept. These medications help improve arthritis all over the body and also help reduce inflammation in skin from psoriasis.
• Regular exercise
• Physical therapy to improve and maintain muscle and joint function

Follow-up care

Your child should be routinely monitored by a pediatric rheumatologist. Prompt treatment can help lessen psoriatic arthritis symptoms.

Regular examinations by an ophthalmologist are also recommended for children with psoriatic arthritis because of the strong connection between JIA and eye disorders. The frequency of eye exams will depend on your child’s age and whether the ANA antibody is present.

Children with skin psoriasis should also be monitored by a dermatologist.