Autoimmune disease – why one often follows another

Autoimmune diseases are becoming increasingly common, with the number of new cases of some conditions rising by as much as 9% each year (1). Approximately 4 million people in the UK are living with an autoimmune disease including: more than 100,000 people living with MS, 400,000 people with type 1 diabetes, more than 400,000 with rheumatoid arthritis and over 2 million people with hypothyroidism (2), (3).

That said, the prevalence of multiple autoimmune syndrome (MAS) – the incidence of 3 or more autoimmune diseases in a single individual, is also on the rise (4,5). Around 25% of patients with an autoimmune disease tend to develop additional autoimmune diseases (6).

A number of factors have been thought to contribute to the development of multiple autoimmune diseases. These include environmental triggers, such as a viral illness or prolonged exposure to certain toxic chemicals, as well as genetic factors.

What is an autoimmune disease?

Autoimmune diseases develop from a dysfunction of the immune system, where it mistakenly attacks your body.

Normally, the immune system is constantly on the lookout for foreign bodies and will send out an army of fighter cells to attack them.

However, in an individual with an autoimmune disease, the immune system mistakes parts of your body, like your joints or skin, as foreign. In this instance, it releases proteins called autoantibodies that attack healthy cells.

Several autoimmune diseases only attack one part of your body such as type 1 diabetes which damages the pancreas. Other diseases, like systemic lupus erythematosus (SLE), affect the whole body.

Common autoimmune diseases

There are more than 80 autoimmune diseases. Here are 7 of the most common.

• Type 1 diabetes
• Thyroid disease (Hashimoto's and Graves')
• Coeliac disease
• Multiple sclerosis
• Rheumatoid arthritis
• Addison’s disease
• Pernicious anaemia

The symptoms

The symptoms for autoimmune diseases vary depending on the type of autoimmune condition. However, some the most common symptoms are;

• Fatigue
• Skin rashes
• Achy joints
• Swelling and redness
• Hair loss
• Numbness and tingling in the hands and feet

Symptoms for autoimmune diseases such as psoriasis or rheumatoid arthritis often worsen during a flare-up and reduce during remission.

What causes autoimmune diseases?

The exact cause of autoimmune diseases remains a mystery, although there are many studies that indicate several theories about what causes the immune system to malfunction.

One thought is that autoimmune diseases such as MS and lupus run in families and are passed on through genetics. Not every family will have the same condition, but they are more at risk of inheriting an autoimmune disease.

According to one study, women get autoimmune diseases at a rate of about 2 to 1 compared to men – 6.4 percent of women vs. 2.7 percent of men (7). It is common for the disease to start during a woman’s childbearing years (ages 15 to 44).

Another suspected risk factor for developing an autoimmune disease is the “Western diet”. Consuming a diet which consists of high fat, high sugar and highly processed food has been linked to an increase of inflammation within the body. While it has not been proven yet, inflammation is thought to play a role in the development of several autoimmune diseases.

What is multiple autoimmune syndrome (MAS)?

Multiple autoimmune syndrome can be defined as the co-existence of at least three or more autoimmune diseases in one individual. The co-existence of more than five autoimmune diseases is extremely rare.

When a person develops additional autoimmune diseases, one of them is usually a dermatological (skin) condition, often being vitiligo or alopecia areata.

Multiple autoimmune syndrome can be classified into three categories; type 1, type 2 and type 3. The classification scheme can be helpful when trying to pinpoint a new autoimmune disease in a patient who has had two previous autoimmune diseases.

What causes MAS?

The fundamental mechanism of multiple autoimmune syndrome is not fully understood and requires further research. Nevertheless, many researchers suspect that genetic, infectious and psychological factors are involved.

Results from a study found that in 10 autoimmune diseases with began in childhood, there were 22 gene signals shared by two or more of the diseases and 19 shared by at least three of the autoimmune diseases.

Several of the gene signals identified were on pathways linked to cells and signalling that play a significant role in the immune system – and autoimmune processes, specifically (8).

Other studies suggest that when immunomodulatory drugs (drugs which alter the immune system) are given to treat an autoimmune disease, changes to the immune system may actually trigger the start of another autoimmune disease (9).

References

1. CIR (2018). [online] Immunology.org. Available at: https://www.immunology.org/sites/default/files/Immunology_News_March_2019_FINAL_web_1.pdf [Accessed 30 Aug. 2019].
2. MMSociety (2018). Ground-breaking research into autoimmune conditions. [online] Mssociety.org.uk. Available at: https://www.mssociety.org.uk/research/latest-research/latest-research-news-and-blogs/ground-breaking-research-into-autoimmune-conditions [Accessed 30 Aug. 2019].
3. QOF (2014). Hypothyroidism-UK - QOF Database. [online] Gpcontract.co.uk. Available at: https://www.gpcontract.co.uk/browse/UK/Hypothyroidism/14 [Accessed 5 Sep. 2019].
4. Anaya, J., Castiblanco, J., Rojas-Villarraga, A., Pineda-Tamayo, R., Levy, R., Gómez-Puerta, J., Dias, C., Mantilla, R., Gallo, J., Cervera, R., Shoenfeld, Y. and Arcos-Burgos, M. (2012). The Multiple Autoimmune Syndromes. A Clue for the Autoimmune Tautology. Clinical Reviews in Allergy & Immunology, 43(3), pp.256-264.
5. Rojas-Villarraga, A., Amaya-Amaya, J., Rodriguez-Rodriguez, A., Mantilla, R. and Anaya, J. (2012). Introducing Polyautoimmunity: Secondary Autoimmune Diseases No Longer Exist. Autoimmune Diseases, 2012, pp.1-9.
6. Cojocaru, M., Cojocaru, I. and Silosi, I. (2010). Multiple autoimmune syndrome. A Journal of Clinical Medicine, 5(2), pp.132-134.
7. Hayter, S. and Cook, M. (2012). Updated assessment of the prevalence, spectrum and case definition of autoimmune disease. Autoimmunity Reviews, 11(10), pp.754-765.
8. Li, Y., Li, J., Zhao, S., Bradfield, J. and Mentch, F. (2019). Meta-analysis of shared genetic architecture across ten pediatric autoimmune diseases. Nat Med, 21(9), pp.1018-1027.
9. Kong, Y., Wei, W. and Tomer, Y. (2010). Opportunistic autoimmune disorders. Annals of the New York Academy of Sciences, 1183(1), pp.222-236.