Juvenile Enthesitis-Related Arthritis (ERA)

What is juvenile idiopathic arthritis (JIA)?

Juvenile idiopathic arthritis (JIA) is arthritis that affects children who are less than 16 years old. It is also called childhood arthritis.

  • Arthritis means "joint swelling" or "joint inflammation". Arthritis leads to pain, swelling, stiffness and loss of motion in the joints.
  • "Idiopathic" means that we do not know the cause.

What is enthesitis-related arthritis (ERA)?

There are many different types of arthritis. Enthesitis-related arthritis (ERA) is one type. Arthritis is a disease that causes pain, swelling, stiffness and loss of motion in the joints. Enthesitis (say: en-tha-SIE-tis) is swelling or inflammation where tendons or ligaments attach to bone. Both enthesitis and arthritis can be seen together in ERA.

Between 10% and 15% of all children with JIA have ERA. It is usually seen in late childhood or adolescence (8 to 15 years of age). It affects boys more often than girls.

The severity of ERA can vary. For some children, it can be mild and last only a short time. For others, it can be more severe and last a long time. Some children may develop inflammation in the back when they are adults.

ERA is sometimes referred to as spondyloarthritis.

ERA is an autoimmune disorder

Inflammation (irritation and swelling) is a normal process in the body. It is how our immune systems protect our bodies from bacteria and viruses that cause infection.

In ERA, like other types of childhood arthritis, there is no infection. Instead, the immune system mistakenly attacks normal cells and tissues. This causes inflammation. Inflammation from ERA leads to redness, swelling, pain, warmth, stiffness, or loss of movement in the joints. For this reason, ERA is called an autoimmune disease. So far, we do not understand what causes these problems.

Signs and symptoms of ERA

Children with ERA have pain, swelling, or stiffness in joints (arthritis). The arthritis is mainly in the lower limbs (the hip, knee, and foot). Arthritis in the back (spondylitis) and the base of the spine at the sacroiliac joint (sacroiliitis) is not as common at first, but can occur later. Children with spondylitis or sacroiliitis often complain of lower back or buttock pain that is worse with rest and better with activity. Arthritis can also occur in the upper limbs, especially the shoulders.

Joints Affected by Enthesitis Arthritis (ERA)
Get Adobe Flash player
Arthritis in the lower joints can be part of ERA. Some children have just the arthritis, some have just the enthesitis, some have a combination of both.

Enthesitis is inflammation of the entheses (say: en-THEE-sees), where tendons and ligaments attach into the bone. The most common areas for enthesitis are the knees, heels, and bottom of the feet. As a result, children with enthesitis report heel, foot or knee pain, with or without swelling. To help with enthesitis pain in the foot and heel, the health care team may recommend supportive footwear and padded heel inserts for your child's shoes.

Entheses Affected by Enthesitis Arthritis (ERA)
Get Adobe Flash player
Entheses are where tendons and ligaments insert into bone. Enthesitis is inflammation of entheses.

Possible other symptoms of ERA

Not all children with ERA will have these other symptoms, but the doctors will always be checking for these:

  • Eye inflammation can occur in up to 30% of children who have ERA. It usually occurs in one eye and can reoccur. Inflammation occurs in the iris, where it is called acute anterior uveitis (say: you-vee-EYE-tis). The eye is usually red, painful, and sensitive to light. Eye inflammation is an emergency. Your child needs to see an eye doctor (ophthalmologist) right away. Your child will need to have routine eye exams with a "slit lamp" to look for early signs of eye inflammation. Please speak to your doctor about how often your child will need to have an eye exam.
  • Skin inflammation can also occur in children with ERA. Inflammation in the skin is called psoriasis (say: sore-EYE-a-sis). This is a persistent skin rash that looks like red patches covered with white scales. It can be found on the scalp, underarms, elbows, and around the belly button.
  • Bowel inflammation can also occur in children with ERA. Inflammation in the intestines is called inflammatory bowel disease (IBD). There are two types of IBD: Crohn's disease, which mostly affects the small intestines, and colitis, which mostly affects the large intestines.

There are several steps to diagnose ERA

The doctor will ask you about your child's symptoms and medical history. The doctor will also do a physical exam to see if your child has any signs of joint inflammation. They may suspect ERA when a child has joint pain and swelling, especially in the lower limbs: pain in the lower back or buttocks; or signs of enthesitis for more than 6 weeks. The doctor will usually order blood tests, X-rays, and sometimes additional tests, like magnetic resonance imaging (MRI), to help diagnose the disease.

One blood test that can be helpful when trying to diagnosis ERA is the HLA-B27 genetic marker. It can tell us who is at higher risk of developing ERA. Most children with ERA are "positive" for the HLA-B27 marker, but it is important to note that:

  • Not every person who carries this marker will have ERA.
  • A child can have ERA and still be "negative" for HLA-B27.

ERA is treated with medicine

ERA is treated with various types of medicine:

  • Some medicine can improve symptoms of inflammation. It helps to reduce pain and stiffness and improve movement in the joints. 
  • Some people with ERA need stronger medicine that suppresses the immune system and helps to control inflammation and prevent joint damage.

For more information, please see "Juvenile Enthesitis Related Arthritis: Treatment", "Living with ERA", "Exercises for Enthesitis and Arthritis", and "Enthesitis-Related Arthritis: A Guide for Teens".

Key points

  • ERA is a disease that causes pain, swelling, and stiffness in the joints of the hips, knees, ankle, feet, and lower back.
  • People with ERA may also have inflammation in the eyes, skin, or intestines.
  • ERA is an autoimmune disease. We do not know why some people get ERA.
  • There are several steps to diagnose ERA. Your child will need various tests.

Shirley Tse, MD, FRCPC
Michelle Anderson, BScN
Kristi Whitney, MSc, BScPT