Juvenile Idiopathic Arthritis
Causes of Juvenile Idiopathic Arthritis
The cause of JIA is unknown.
JIA is an auto-inflammatory disability. [1] This means that the immune system malfunctions and attacks healthy cells in the body, leading to intense swelling in the joints, along with fevers and rashes. [1]
The immune system's job is to protect the body from illness. [1]
The reason for the immune system attacking its own healthy cells is unknown.
Children who get JIA have a genetic susceptibility that is triggered by something in the environment. There are a number of environmental triggers that have been proposed.
Genetic Susceptibility
Genetic predisposition only partially explains the cause of JIA.
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The genes that control white blood cell functioning, are not working the right way. [2]
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White blood cells are important in helping the immune system work properly and they do this by fighting harmful cells. [3]
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However, in children with JIA, white blood cell are being turned on and off at the wrong time. [2]
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The reason for this is not known, but it results in the cells in the immune system attacking healthy cells.
The child has a greater chance of having JIA if it runs in the family.
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Siblings have a 12 times higher risk of getting JIA, than someone in the general population. [1]
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Cousins have a 6 times greater risk. [1]
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Twin studies have shown that if one identical twin has JIA, there is a 25-40% chance that the other twin will also have it. [1]
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If JIA was entirely genetic, this chance would be 100%, but since it is not we know that environmental factors play a role.
Remember: It is not your fault if your child has a genetic susceptibility to JIA.
Potential Environmental Triggers
Environmental influences on JIA have received mixed results. These are several of the possible environmental triggers:
Infections During Childhood - Infections caused by viruses and bacteria can trigger the immune system's response. Some of the viruses and bacterial infections that have been associated with JIA are mononucleosis ("mono"), strep throat, scarlet fever, bronchitis, tuberculosis, and pneumonia. [2] It is important to note that if your child contracts one of these, it will NOT necessarily mean that they will get JIA.
Breastfeeding Duration - There is mixed evidence on this topic. Breastfeeding has been shown to protect the child from viruses and bacteria, and reduce the risk of chronic diseases. [2] Some researchers have found that mothers who did not breastfeed their child were more likely to have a child develop JIA. [2]
The "Hygiene Hypothesis" - This hypothesis says that children who are not exposed to various infections during childhood, will have a weaker and less resilient immune system. [4] This leads to an increased risk of contracting auto-inflammatory disorder.
Insufficient Vitamin D Intake - Vitamin D is not only essential for good bone health, but also plays a role in promoting a healthy immune system. [2] Vitamin D deficiency is common in children who have auto-inflammatory disorders because this vitamin influences the immune response. [2] Children should get the recommended intake of Vitamin D in their diet.
To support the "Hygiene Hypothesis", autoimmune disorders such as JIA are less common in developing countries because these countries have more exposure to infections, resulting in a stronger immune system. [4]
Glossary
Gene: a molecule that is inherited and holds information that impacts development
Immune System: Our body's way of staying healthy by getting rid of germs and other unfamiliar objects that enter our system
Auto-Inflammatory Disease: A condition where the immune system attacks its own cells, leading to swelling in various parts of the body for an unknown cause
White Blood Cell: A cell in the body that helps to fight infection and protects the body from germs
References
1. Mary Dunkin,"Is JIA Really an Autoimmune Disease," Kids Get Arthritis Too, accessed March 10, 2017, http://www.kidsgetarthritistoo.org/about-ja/the-basics/ja-autoimmunity.php
2. Justine Ellis, Jane Munro, and Anne-Louis Ponsonby, "Possible Environmental Determinants of Juvenile Idiopathic Arthritis," Rheumatology 49, no. 3 (2010): 411-425.
3. S.H. Abd-Allah, A.S. El-Shal, S.M. Shalaby, H.F. Pasha, A.M. Abou El-Saoud, S.M. Abdel Galil, and T.A. Mahmoud, “Influence of Matrix Metalloproteinase 1 and 3 Genetic Variations on Susceptibility and Severity of Juvenile Idiopathic Arthritis,” IUBMB Life 67, no. 12, (2015): 934-942.
4. "Hygiene Hypothesis," Fortress Biotech, accessed March 11, 2017, http://www.fortressbiotech.com/research-development/hygiene-hypothesis.cfm