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There are six different subtypes of juvenile idiopathic arthritis. One of the subtypes is known as enthesitis-related arthritis. This article outlines the causes, symptoms, diagnosis and treatment for enthesitis-related arthritis.

Juvenile idiopathic arthritis is a type of arthritis that occurs in children and adolescents. There are several subtypes of juvenile idiopathic arthritis, one of which is known as enthesitis-related juvenile idiopathic arthritis. It can also be called pondyloarthritis or ankylosing spondylitis.

This type of arthritis affects between 10 and 15 percent of all children with juvenile idiopathic arthritis and usually manifests either in late childhood or as a teenager, so most children are between the ages of eight and 15. This subtype is more commonly diagnosed in boys compared to girls. The severity of enthesitis-related juvenile idiopathic arthritis varies from individual to individual with some children experiencing mild symptoms that only last a short amount of time compared to others who experience more severe symptoms for a longer period of time.

What is unique about this subtype of arthritis is that — unlike other subtypes where the inflammation associated with arthritis only occurs in the joints or muscles — enthesitis-related juvenile idiopathic arthritis also causes inflammation in the the entheses, the connective tissue where the tendon or ligament meets the bone. Hence, patients with enthesitis-related juvenile idiopathic arthritis develop redness, swelling, pain and stiffness in the entheses.

Causes of enthesitis-related juvenile idiopathic arthritis

Generally, the immune system protects us from foreign pathogens, including bacteria, viruses and fungi. However, in some instances, the immune system does not function normally and starts to identify the body’s own healthy tissue as a threat. Thus, in autoimmune diseases, the immune system attacks healthy tissue and causes inflammation, pain and swelling. Enthesitis-related juvenile idiopathic arthritis is an autoimmune disease in which the immune system attacks the body’s joints, tendons, and entheses.

However, it is still unknown why some people develop enthesitis-related juvenile idiopathic arthritis while others don't, though some studies point to a role for genetics in the development of this disease.

Symptoms of enthesitis-related juvenile idiopathic arthritis

Symptoms of enthesitis-related juvenile idiopathic arthritis come on as flares, which refer to a period of time in which the symptoms are more severe. After flares, the patient goes into remission, in which the symptoms subside.

The following symptoms are associated with development of this disease:

  • Pain, swelling, stiffness, inflammation, and redness of joints in the hips, knees, feet, back and ankles. However, it mainly involves joints of the lower limbs while the back and base of spine are not commonly affected, at least at first. It can also involve joints of the upper limbs, such as the shoulder.
  • Pain in the foot, heel, or knee, which may be accompanied with swelling.
  • The pain, particularly in the lower back or butt, is more severe with rest and improves when the child is more active.
  • A subset of patients may also experience inflammation of the eye, which occurs in up to 30 percent of children with this subtype of arthritis. Generally, eye inflammation in this context develops in one eye, and can recur at a later time. This type of inflammation is known as acute anterior uveitis as it occurs in the iris of the eye. Symptoms of eye inflammation include having a red eye that is painful and sensitive to light. If this occurs in a child, it is important to take them to a doctor right away as if it is left untreated, it can damage the child’s vision. Generally, children with this subtype of arthritis frequently see an eye specialist and have regular eye check-ups to make sure nothing is going undetected and untreated.
  • Another small proportion of patients will develop a disease characterized by skin inflammation, known as psoriasis. Symptoms of this skin disease include red, scaly skin on the scalp, underarms, elbows or belly button.
  • Some patients can also develop inflammation of the intestine, known as bowel inflammation. This type of disease is known as inflammatory bowel disease, and patients have one of two different inflammatory bowel diseases, Crohn's disease and ulcerative colitis.

Diagnosis: How is enthesitis-related juvenile idiopathic arthritis diagnosed?

If your child’s doctor suspects that your child may have arthritis, they will refer you to a specialist known as a rheumatologist. In order to make a diagnosis of enthesitis-related juvenile idiopathic arthritis, the rheumatologist will first ask detailed questions about the child’s symptom, conduct a medical personal and family history, do a physical exam, and order tests. These tests include:

  • Blood tests, which will look for signs of inflammation and anemia (low red blood cell count).
  • A genetic test to look for a gene known as HLA-B27 that is more common in patients with enthesitis-related juvenile idiopathic arthritis. In fact, most children with this subtype will be positive for the presence of HLA-B27. However, if a child is negative for the gene, it does not mean that they do not have the disease.
  • Imaging tests such as X-rays and MRIs to look for severity of joint damage and to exclude other disease possibilities.

Treatment: How is enthesitis-related juvenile idiopathic arthritis managed?

As there is no cure for arthritis, doctors focus on treating the symptoms associated with the disease. Some medical treatments for the disease include:

  • Non-steroidal anti-inflammatory drugs (NSAIDs). These drugs help reduce inflammation, swelling and pain. Many NSAIDs are available over-the-counter and include ibuprofen (Advil) and naproxen (Aleve).
  • Corticosteroids. These are powerful anti-inflammatory medicines, such as prednisone, that can significantly reduce inflammation.
  • Biologic therapies. These drugs help treat the underlying inflammation and can be prescribed if NSAIDs or corticosteroids don’t work. These help suppress the immune system and prevent damage to the joints.

  • Colbert, Robert A. "Classification of juvenile spondyloarthritis: Enthesitis-related arthritis and beyond." Nature Reviews Rheumatology 6.8 (2010): 477.
  • Ravelli, Angelo, and Alberto Martini. "Juvenile idiopathic arthritis." The Lancet 369.9563 (2007): 767-778.
  • Photo courtesy of SteadyHealth.com

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