Enthesitis-related arthritis is a form of juvenile idiopathic arthritis that typically first appears in males ages 6–15. Treatments are available to manage symptoms and may even help you achieve remission.

Enthesitis-related arthritis (ERA) is one of several types of juvenile idiopathic arthritis (JIA). These childhood autoimmune conditions begin before the child’s 16th birthday and can evolve, flare, or improve over time.

Enthesitis is the painful inflammation of the entheses, the fibrous connective tissue that attaches your tendons and ligaments to your bones. There are over 100 entheses in your body.

In ERA, your immune system mistakenly attacks both joints and entheses, leading to inflammation. Children with ERA may have swelling, pain, and stiffness of multiple joints and entheses, along with other symptoms.

Although ERA is a chronic disease, treatment can manage symptoms and even cause them to go into remission.

Common symptoms include:

  • enthesitis (pain where tendons or ligaments join bones), most often at the lower part of the kneecap and the heel
  • arthritis (pain, swelling, and stiffness) of any joint, most often the hip, knee, ankle, shoulder, and sacroiliac joint
  • fever
  • uveitis (painful red eye, vision changes)
  • gut inflammation ranging from mild, nonspecific symptoms to inflammatory bowel disease

Enthesitis-related arthritis vs. ankylosing spondylitis

ERA is part of the spectrum of juvenile idiopathic arthritis (JIA). Symptoms always start by age 16, and the arthritis can begin in any joint in the body.

Ankylosing spondylitis (AS) diagnoses usually occur in adults, but the disease can occasionally begin in childhood. In juvenile ankylosing spondylitis (JAS), autoimmune arthritis always inflames the joints of the spine.

ERA and JAS have many similarities. Some children with ERA can develop inflammation of the spine, and some people with JAS will also develop enthesitis or arthritis in places other than the spine. Both ERA and JAS are commonly associated with positive HLA-B27 genetic tests, and both can run in families.

As their condition evolves, some children with ERA may end up meeting the diagnostic criteria for juvenile or adult forms of AS. But this is not always the case.

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ERA and other forms of JIA are inflammatory autoimmune disorders. In these conditions, your immune system mistakenly begins attacking your own body.

In ERA, your immune system attacks your joints and entheses, causing inflammation, pain, and swelling at affected sites.

Doctors aren’t yet sure what causes the immune system to misfire. They suspect a combination of:

  • genetic risk factors
  • infections
  • microtrauma to the entheses
  • other environmental triggers

ERA usually develops in middle childhood, around age 6–15 years. It’s more frequent in males than females.

Compared with other JIA types, ERA is more common in people of Asian descent.

Your doctor will discuss your child’s symptoms and family medical history, perform a physical exam, and order blood tests. Imaging tests like X-rays, ultrasounds, or MRIs may also help.

Your child may also need to see other specialists to help diagnose and treat ERA, such as:

Types of juvenile idiopathic arthritis

JIA includes several different types of childhood autoimmune arthritis. All children with JIA have otherwise unexplained arthritis in at least one joint.

In addition to ERA, other types of JIA include:

  • Systemic: affects any number of joints and causing prolonged fevers, enlarged spleen or liver, and serositis
  • Oligoarticular: affects fewer than five joints
  • Polyarticular: affects five or more joints
  • Psoriatic: affects any number of joints in people, often with a family history of psoriasis, accompanied by dactylitis and abnormal nail findings
  • Undifferentiated: affects any number of joints without fitting into any of the above categories (or meeting criteria for multiple types)
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If your child receives a diagnosis of ERA, you’ll see both a primary care pediatrician and a rheumatologist who specializes in immune-mediated conditions. Depending on symptoms, your child might also see an ophthalmologist, gastroenterologist, or physical or occupational therapist.

Medications help treat ERA symptoms and prevent damage to your joints. Your doctor might suggest anti-inflammatory therapies like:

In certain circumstances, a doctor might consider steroid injections into the joint or enthesis.

Exercise regimens encouraging stretching and flexibility, supportive shoe inserts, and ice application can also help you manage symptoms and stay active.

ERA is a chronic autoinflammatory disease requiring long-term monitoring and treatment. Research suggests that children with ERA experience more persistent problems with pain and function than those with other forms of JIA.

Children with ERA often experience evolving symptoms into adulthood. But symptom management and even complete remission are possible.

Only a few studies have explored long-term outcomes in children with ERA. One older study found that approximately 15 years after diagnosis, 44% of ERA patients were in remission, though long-term complications such as reduced spinal flexion were common.

In 2016, researchers published a follow-up study of JIA patients 30 years after diagnosis. They found that 59% were in clinical remission and off medication.

Research also suggests that your long-term outlook with ERA may be poorer if you experience hip or knee arthritis.

Fortunately, advances in both treatment and monitoring for children diagnosed with ERA are ongoing.

What causes enthesitis to flare?

Enthesitis can happen in people who do not have autoimmune disease. One common trigger is sports overuse injury.

In children with ERA or other forms of JIA, the initial trigger causing autoimmune inflammation is unknown. Once you receive a diagnosis, disease flare-ups can also happen without obvious cause. Possible triggers include:

  • viral illness or infections
  • poor sleep
  • medication changes
  • missed medication doses

How rare is enthesitis-related arthritis?

JIA is one of the most common autoimmune diseases of childhood. Experts estimate 294,000 U.S. children are currently living with JIA. About 15–20% of these have ERA.

At what age does enthesitis-related arthritis occur?

ERA is a childhood disorder. Though symptoms may persist and evolve into adulthood, they must begin by age 16.

ERA is most common in male children ages 6 and older. Research shows that, on average, symptoms generally begin around 10–15 years of age.

ERA is a childhood autoinflammatory arthritis disorder. It is part of the spectrum of JIA.

Unlike most other forms of JIA, ERA tends to appear slightly later (around age 10–15) and is more common in males. ERA is also more prevalent in people of Asian descent.

ERA causes pain, swelling, and stiffness at affected joints and entheses, the tissue connecting tendons and ligaments to bones. ERA can also cause non-joint-related symptoms like fevers, eye problems, or gastrointestinal issues.

ERA is a chronic disease. Symptoms may evolve and change, and relapses can occur well into adulthood. Treatments are available to help manage symptoms and prevent joint damage. Advances in therapy are ongoing.