Psoriatic arthritis combines the symptoms of arthritis and psoriasis. It makes your joints achy and swollen, and causes red, scaly sores to form on the skin.

Psoriatic arthritis is an autoimmune disease. That means your immune system mistakenly identifies parts of your own body as foreign invaders and attacks them.

This immune system attack causes your body to produce skin cells at a much faster rate than usual. These cells build up on your skin and form the scaly plaques. Your immune system can also attack your joints, causing pain, swelling, and stiffness.

About 7.5 million Americans have psoriasis. Around 2.25 million people in this group have psoriatic arthritis.

Although psoriatic arthritis is most common in adults ages 30 to 50, children can get it too. It’s estimated that 1 to 10 out of every 33,000 children is diagnosed with psoriatic arthritis.

However, the real number could be higher. Doctors sometimes misdiagnose psoriatic arthritis in children, because the rash appears years after the joints have been affected.

Juvenile psoriatic arthritis is considered a type of juvenile idiopathic arthritis (JIA). This is the most common form of arthritis in children. “Idiopathic” means doctors don’t know what causes it.

Children usually have the same psoriatic arthritis symptoms as adults. These include:

  • swollen, red, and painful joints, especially in the fingers and toes
  • stiffness in the morning
  • swelling in the hands that makes the fingers and toes look like sausages
  • a red, itchy, and scaly rash on the knees, elbows, scalp, face, and buttocks
  • joints that are deformed from swelling
  • pitted nails
  • fatigue
  • red, irritated eyes

Sometimes, psoriatic arthritis symptoms affect one side of a child’s body more than the other.

Learn more: Put a stop to psoriatic arthritis pain »

Doctors don’t know what causes the immune system to turn against the joints and skin. They think the disease stems from both genes and environmental exposures in children and adults. Children with juvenile psoriatic arthritis often have a relative with the disease.

Most kids get juvenile psoriatic arthritis between the ages of 6 and 10. Both boys and girls can get the condition, although it’s slightly more common in girls. Having a parent, sibling, or other close relative with psoriatic arthritis increases a child’s risk.

Joint damage at such a young age can lead to long-term growth problems.

Kids with juvenile psoriatic arthritis can have:

  • shorter-than-normal bones
  • slowed growth
  • problems with the jaw that can make it hard for them to brush their teeth
  • an increased risk for osteoarthritis and osteoporosis as they age

Psoriatic arthritis can also affect other parts of a child’s body. This can cause swelling of membranes around the heart or lungs and swelling in the eye (uveitis).

Getting your child treated early can help prevent these complications.

During the exam, your doctor will ask about your child’s symptoms and family medical history.

To diagnose kids with psoriatic arthritis, doctors look for the following:

  • sausage-like fingers or toes
  • pits in the nails
  • psoriasis rash
  • a close relative with psoriasis

No one test can confirm that your child has psoriatic arthritis. These tests can help your doctor rule out other diseases with similar symptoms:

  • Antibody blood tests: Antinuclear antibody (ANA) and other auto-antibody tests can show signs of an immune system reaction.
  • Uric acid test: Uric acid is a chemical your body produces when it breaks down foods that contain organic compounds called purines. People with psoriatic arthritis sometimes have high uric acid levels.
  • X-rays: This test uses a small amount of radiation to make pictures of the bones and joints. It can show damage caused by arthritis.
  • MRI: This test uses magnets and radio waves to make pictures inside the body. An MRI can show damage to the bones and joints, as well as soft tissue changes that don’t appear on X-rays.
  • Eye exam: Eye tests look for inflammation called uveitis.

Children with psoriatic arthritis will need to see a few types of doctors:

  • pediatrician
  • a doctor who treats joint diseases in children (pediatric rheumatologist)
  • an eye doctor (ophthalmologist)

The goal is to bring down swelling in the joints and prevent more damage. Your child’s treatment will depend on their age and the severity of their symptoms.

A typical treatment plan for children with psoriatic arthritis may include:

  • nonsteroidal anti-inflammatory drugs such as aspirin (Ecotrin) and ibuprofen (Motrin) to bring down swelling and relieve pain
  • calcium and vitamin D to strengthen the bones
  • physical therapy and exercise to strengthen the joints and keep them mobile
  • occupational therapy to help your child do everyday tasks more easily
  • hydrotherapy, or exercise in a warm pool, to loosen the joints
  • splints to keep the joints in the correct position and prevent pain

If these treatments don’t work, your child’s doctor might prescribe stronger medicines, such as:

  • steroid drugs injected into the affected joints to bring down swelling
  • biologic medicines, such as infliximab (Remicade) or golimumab (Simponi), that slow or stop joint damage

Check out: Best natural remedies for psoriatic arthritis »

Children who are treated early can go into remission. Though they’ll still have psoriatic arthritis, they won’t show symptoms. Physical therapy and occupational therapy can help reduce the impact of this disease on your child’s daily life.

Kids who don’t get treated early can develop a lot of joint damage that could lead to disability.

Keep reading: Foods to avoid to prevent psoriatic arthritis flare-ups »