What Is Multiple Autoimmune Syndrome?

Multiple autoimmune syndrome, by definition, is the combined occurrence of at least three autoimmune diseases in the same person. About 25 percent of those with an autoimmune disease have a tendency or likelihood of developing other autoimmune diseases as well. People with multiple autoimmune syndrome usually have at least one dermatological (skin) condition, which commonly is vitiligo or alopecia areata. The co-occurrence of five autoimmune diseases is considered extremely rare.

Classifications of Multiple Autoimmune Syndrome

A classification scheme was developed for people with two autoimmune diseases based on the prevalence of certain conditions occurring together. The classification scheme, which separates multiple autoimmune syndrome into three types, is useful for detecting a new condition when symptoms first appear. It helps determine where the third condition most likely "fits in."

• Type 1 Multiple Autoimmune Syndrome: myasthenia gravis, thymoma, polymyositis, giant cell myocarditis
• Type 2 Multiple Autoimmune Syndrome: Sjögren's syndrome, rheumatoid arthritis, primary biliary cirrhosis, scleroderma, autoimmune thyroid disease
• Type 3 Multiple Autoimmune Syndrome: autoimmune thyroid disease, myasthenia gravis and/or thymoma, Sjögren's syndrome, pernicious anemia, idiopathic thrombopenic purpura, Addison's disease, type 1 diabetes mellitus, vitiligo, autoimmune hemolytic anemia, systemic lupus erythematosus, dermatitis herpetiformis

Cause of Multiple Autoimmune Syndrome

The underlying mechanism that leads to multiple autoimmune syndrome is not fully understood. That said, researchers suspect that environmental triggers and genetic susceptibility are involved. It is also known that certain autoantibodies are present in certain conditions and multiple organ systems may be affected. Because multiple autoimmune conditions can occur in the same person, or within a family, an immunogenetic mechanism associated with autoimmunity is involved.

Results from a meta-analysis published in Nature Medicine (2015) revealed that in 10 autoimmune diseases with onset 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. Many of the gene signals discovered were on pathways linked to cell activation, cell proliferation, and signaling systems that play a significant role in the immune system—and autoimmune processes, specifically. The 10 autoimmune diseases were type 1 diabetes, celiac disease, juvenile idiopathic arthritis, common variable immunodeficiency disease, systemic lupus erythematosus, Crohn's disease, ulcerative colitis, psoriasis, autoimmune thyroiditis, and ankylosing spondylitis. 

Other genome-wide association studies have found hundreds of susceptibility genes among autoimmune diseases that primarily affect adults. While identifying the genes helps us to understand the cause of multiple autoimmune syndrome, it may also lead to more targets for treatment.

While some combination of genetic associations and environmental triggers is the current thinking, other possibilities have been put forth by researchers. It has been suggested that when immunomodulatory drugs are introduced to treat one autoimmune disease, changes to the immune system may occur which set in motion the development of another autoimmune disease.

Two or More Autoimmune Diseases in Rheumatology

Co-occurrence of two or more autoimmune diseases is not considered uncommon. It is commonly seen with systemic lupus erythematosus, rheumatoid arthritis, scleroderma, Sjögren's syndrome, vasculitis, and polymyositis.

Studies have shown that rheumatoid arthritis and autoimmune thyroiditis are among the most common autoimmune diseases found in the general population. According to Healio Rheumatology, if someone has one of the two conditions, their risk of developing the other is 1.5 times higher than for those without either condition.

Interestingly, there is an inverse relationship between rheumatoid arthritis and multiple sclerosis, meaning that if you have one of the two conditions, there is decreased susceptibility to develop the other. While we can surely call this a curious observation, genetic variants may offer the reason for it.

It is worth mentioning that autoimmune diseases are much more prevalent among women than men. The gender difference adds a layer of complication for researchers who try to ascertain the risk of developing a second autoimmune condition or multiple autoimmune syndrome. Is the risk the same for males and females? So much is yet to be learned.

A Word From Verywell

For people who have one autoimmune condition, there must be continued vigilance for the development of other autoimmune conditions. It is known that multiple autoimmune diseases occur with increased frequency among those who have at least one autoimmune condition. Always discuss changes that you observe in your condition with your healthcare provider. Early diagnosis and treatment work in your favor.