Enthesitis Related Arthritis is a form of arthritis that begins in people under 16 years of age.  Although it is more commonly diagnosed in boys, girls can also have ERA.  Onset is usually between the ages of 9-12.

ERA is also sometimes simply called enthesitis.  If a child has been diagnosed with enthesitis by a pediatric rheumatologist and requires long-term follow-up, verify with the doctor that the full name of the disease is ERA aka enthesitis-related juvenile idiopathic arthritis.  Not only is enthesitis one of the forms of JIA, but it is also part of a group of diseases called spondyloarthropathies.

This type of arthritis is significantly different from osteoarthritis, which is the type of arthritis typically seen in older people and athletes. In osteoarthritis (OA), the cartilage cushion at the joint between two bones wears away.   Bone-on-bone is extremely painful.  With OA, tylenol can help.  So can surgery to replace grandma’s worn-out joint.  In stark contrast, ERA is an autoimmune disease (from G. autos – self, and L. immunus – from which we get our word “immune”).  In autoimmune diseases, the immune system commits treason and turns on the body’s tissues that it’s supposed to be protecting.  Tylenol does not help.  A full-body attack by the immune system is dramatically different than the wearing away of a single joint.

To understand ERA, a quick anatomy review is helpful:

  • ligaments attach bones to one another
  • tendons attach muscles to bones

The point at which ligaments and tendons attach to the bone is called the enthesis (plural entheses).  In Enthesitis Related Arthritis, the entheses are inflamed.



The pain of enthesitis can be very similar to tendonitis and bursitis.   Such pain without an injury to cause it can be puzzling.  Often, children with ERA complain that their heels hurt.  Or perhaps it’s their feet or knees.  Around the knee, tender spots are at 6:00, 10:00, and 2:00 circling the patella. Other common sites are the Achilles tendon insertion points, and the plantar fascia attachments. This pain can lead to limited range of motion.

In ERA, it’s typically the larger joints of the lower extremities that are painful, so hips are sometimes involved.  Shoulders can also be affected.  Later on, there might be spinal (back and neck) involvement.  Other symptoms of ERA can be weight loss, lack of appetite, abnormally slow growth, and Irritable Bowel Disease.


Enthesitis Related Arthritis is not limited to joints; it is systemic.  That means organ tissues can be affected.  With ERA patients, it is particularly important to watch the eyes for signs of uveitis.  Acute anterior uveitis occurs in 27% of ERA patients.

Another disease linked to ERA is IBD, ie Crohns or ulcerative colitis.  Flares of IBD coincide with flares of ERA.

Dental problems seem to be more common with JIA, perhaps because children are extremely sore and don’t brush as well as they ought.  Attention to good oral hygiene is important.

Diagnostic Criteria

There are two different ways that a child can qualify for an ERA diagnosis.

  • Both arthritis (joint inflammation) and enthesitis (inflammation of a tendon-insertion site),


  • Either arthritis or enthesitis, and at least two of the following
    • inflammation of the sacroiliac joints
    • positive HLA-B27 blood test
    • arthritis in males age 7-16 (some lists say ages >8)
    • a parent, full-sibling, half-sibling, aunt, uncle, niece, nephew, or grandparent diagnosed with a spondyloarthropathy (ie AS, USpA, ERA, or SI-joint inflammation plus IBD)
    • Acute anterior uveitis


Like all idiopathic diseases, the cause of ERA is unknown.  This disease is not hereditary, although there can sometimes be a genetic component.  There is a link to the HLA-B27 gene, however not everyone with the gene develops ERA, and not everyone with ERA has the gene.

ERA, like all forms of JIA, is not contagious.


The goal is to allow kids to live a normal life, so treatment will be multifaceted.

  • A professionally-developed stretching and exercise plan is important for the purpose of relieving pain, protecting joints, improving joint function, strengthening muscles to allow smooth movement of joints, and keeping heart, lungs, and bones strong.  A physical therapist can help design a good exercise routine, and will usually focus on the lower extremities and large joints.  An occupational therapist will contribute to the exercise routine, too, focusing on the upper extremities and small joints/fine-motor skills.
  • Medication will be used to reduce inflammation and pain, and slow progression of the disease.  A good relationship with your pharmacist can be helpful.
    • The first-line treatment of ERA is Non-Steroidal Anti-Inflammatory Drugs such as prescription-strength ibuprofen, meloxicam, or dicofenac.  NSAIDs must be taken religiously to be effective, and must be taken with food to protect the stomach.
    • If NSAIDs do not provide sufficient relief, Disease Modifying Anti-Rheumatic Drugs can be prescribed.   There are many different DMARDs.  If inexpensive DMARDs such as sulfasalazine and methotrexate are not effective enough, another class of DMARDs, called biologics or Biologic Response Modifiers can be prescribed.
    • Steroids such as prednisone can be extremely helpful short-term.  These medications can cause problems such as skin thinning, weight-gain, and moon-face when taken long-term, so doctors will prescribe them cautiously.  Steroids should not be stopped abruptly.  It is extremely important to follow a doctor’s tapering schedule when discontinuing prednisone and other steroid medications.
  • Dietary modification might be needed to include all vitamins and eliminate foods that trigger symptoms.  Anecdotes abound of children whose symptoms improve when they eliminate trigger-foods from their diet.  This is particularly true of people with IBD, but helps others, too.  Common triggers are gluten, dairy products, nightshades, and sugar.  Rheumatologists will sometimes write a referral to a dietician.
  • Counselling, if needed, can help children and families deal with the psychological aspect of living with a chronic disease.
  • Professional eye care will be needed to treat uveitis if it occurs.

Children experiencing a flare-up of symptoms are sometimes soothed by the application of heat to the affected joint.  Heating pads and hot water bottles are quite helpful.


This is a chronic condition, meaning that the goal of treatment is to minimize symptoms and slow possible disease progression.  There is not yet a cure.  Some children diagnosed with ERA will deal with it their entire lives.  Some go into remission.  A better outcome is anticipated when the arthritis is limited to peripheral joints.  When the disease is more aggressive, sacroilliac joints and spine are involved.  Remission rates range between 17% to 37%.


Q&A About Juvenile Arthritis
Juvenile Enthesitis-Related Arthritis
Exercises for Enthesitis and Arthritis
Enthesitis-Related Arthritis: A Guide for Teenagers
Enthesitis Related Arthritis – MedScape
Enthesitis Related Arthritis – OrphaNet
Outcome in patients with enthesitis related arthritis
Classification of juvenile spondyloarthritis: enthesitis-related arthritis and beyond
Juvenile Spondyloarthropathies
Juvenile Idiopathic Arthritis (page 4)
Early Identification of Juvenile Idiopathic Arthritis
Juvenile Idiopathic Arthritis >> Forms
JIA for the Primary Care Practitioner
Arthritis in Children



When I see my doctor, he doesn’t assume that I’ve reported every symptom; he takes what I’ve reported, looks for patterns, and asks questions to try to fill in the missing pieces so he can get an accurate picture of what’s going on.  I thought all doctors were trained to do that.

Some are obviously better at it than others.  Throughout her high school years, my niece saw pediatric cardiologists and pediatric neurologists.  Now she is in her second year of college and seeing an internist.  Last week I heard that she is trying to juggle classes and doctor appointments, and they suspected Crohns.  Crohns is linked to the spondyloarthropathies.  My niece has Raynauds and symptoms of Crohns.

I emailed my niece a few links so she could read about Crohns and some of the related arthritic diseases.  She called me after reading them.  Joint pain?  Nobody ever asked her about joint pain.  She’s had joint pain since she was twelve years old!  Knees, hips, and ankles are affected, sometimes shoulders; she has long-term, bilateral joint pain.  She doesn’t think to say anything about it; nor does she make an issue of the fact that she breathes regularly.  When something is always there, you don’t think to mention it.  She just buys ibuprofen in Costco-sized bottles and tries to make the best of things.

Autoimmune diseases such as RA and JIA have a genetic component.  It amazes me when this link is ignored.  I have Raynauds and RA/USpA.  My daughter has Raynauds and ERA.  We believe that my father had undiagnosed autoimmune arthritis.  My niece has Raynauds and a variety of other health problems that could all be explained as complications of JIA.  Even without our family history, it seems like the combination of Raynauds with other symptoms linked to autoimmune diseases would make a doctor include JIA in his list of possibilities to be investigated.

After a long talk with my niece, I’m fairly sure that she would benefit from a thorough exam by a rheumatologist.  Now she needs to figure out how to track symptoms (after figuring out which symptoms to track), record what she does that makes things better or worse, any other pertinent data (without knowing what might or might not be pertinent), and respectfully present information to her doctor in a way that will make him consider whether or not she’s had undiagnosed JIA for the past eight years.

It is astonishing that no doctor has ever asked the right questions to put the pieces together.  Unbelievable.

Suggestions on what data my niece should track,
and how to artfully feed her doctor the right information
so  that he can accurately determine whether or not
she should be referred to rheumatology
would be much appreciated.
Message me if you’d prefer to remain off-the-record:

Recognizing Arthritis in Kids

Old people can develop osteoarthritis  when the cartilage wears away at a joint, leaving no cushion between two bones.  The arthritis that kids get is very different – it’s actually an attack by the immune system and has nothing to do with the degeneration of cartilage.

The number of new cases of children diagnosed annually with arthritis is quite low.  Depending on the country doing the reporting, incidence is only 1-22 cases per 100,000 children.  This means that most doctors are not going to diagnose a new case of juvenile arthritis – it just doesn’t show up that often.

It’s important, then, for doctors – and parents searching for answers – to recognize that:

  1. kids do get arthritis, and
  2. there are different types of juvenile arthritis.

The least common type of juvenile arthritis is enthesitis, characterized by inflammation where tendons attach to the bone.  It is most commonly seen in boys aged 9-15, and is easily dismissed as growing pains.  This disease often affects large joints such as hips, shoulders, and knees; spinal involvement occurs later in the disease.  Enthesitis Related Arthritis can also include spondyloarthropathy, ankylosing spondylitis and irritable bowel disease.  Redness and swelling do not necessarily accompany the joint pain of ERA.  27% of ERA patients have uveitis, so eye exams are important.

Juvenile psoriatic arthritis can occur in children who do not have psoriasis.  This presents a challenge for the diagnostician, because skin involvement can take years to develop.  The arthritis is not necessarily symmetrical, and lab work will show a negative rheumatoid factor.

Systemic JIA was formerly called Stills Disease.  The typical SJIA patient is a young anemic child, either boy or girl, with a high fever and a rash.  Labs show elevated CRP, ESR, white count, and platelet count.  Diagnosis can be difficult because joint involvement does not necessarily occur at the same time as the initial fever and rash.  The remission rate is 60%-87%.

Affecting five or more joints in the first six months of disease, polyarticular JIA patients are at risk of uveitis.  Polyarthritis is divided into two different types:

Seropositive polyarticular JIA (blood test for rheumatoid factor is positive) usually affects adolescent girls.  Joint involvement is symmetric.  This disease is very similar to adult rheumatoid arthritis.

Seronegative polyarticular JIA (blood test for rheumatoid factor is negative) usually affects young girls and has a better prognosis than those who are RF+.

The most common type of juvenile idiopathic arthritis is oligoarticular.  Children with oligoarticular JIA are always RF negative, but about 70% have a positive ANA.  This type of JIA affects fewer than five joints during the first six months of disease.  Textbook presentation is little girls age 1-4, with a swollen (not necessarily painful) knee or ankle.

After six months, if there are still fewer than five joints affected, the diagnosis is  persistent oligoarticular JIA; this group of patients has a 75% remission rate.

If additional (5 or more) joints are affected after six months, the diagnosis is extended oligoarticular JIA; this group of patients has a 12% remission rate.

It is important to check the eyes of kids with oligoarticular JIA, because asymptomatic uveitis is a significant risk.

Undifferentiated is the JIA that refuses to be put in a box.  These kids have arthritis, but

  • don’t meet all the criteria for a specific diagnosis in one of the above-mentioned subclasses, or
  • meet the criteria for more than one subclass, but are RF+ or have a close relative with psoriasis

My daughter who took four years to be diagnosed with ERA would like to remind you that diseases don’t read textbooks.  Kids who complain of joint pain need to be followed diligently until a diagnosis is reached.

For further reading:

Arthritis in Children, American College of Rheumatology
Questions and Answers about Juvenile Arthritis, NIAMS
Juvenile Idiopathic Arthritis, Orphanet
Growing Pains: The ILAR Classification of Juvenile Idiopathic Arthritis, Journal of Rheumatology
Early Identification of Juvenile Idiopathic Arthritis, Musculoskeletal Network