When doctors consider a potential autoimmune disease diagnosis, they look at various factors. Symptoms, lab and imaging results, medical history, lifestyle, and family history can each indicate a potential condition.
If your doctor asks about your family medical history, they are likely trying to assess your genetic risk. But, are autoimmune diseases genetic? If so, how much of a role do your genes play in autoimmunity?
How are genetics involved in an autoimmune disease diagnosis?
There are two types of genetic risk (or predisposition): monogenic and polygenic. Monogenic risk means that a single gene causes mutations and therefore, disease risk. Polygenic risk means that the interaction of multiple genes causes a genetic predisposition.
In 2007, the entire human genome was being investigated using a method called genome-wide association studies (GWAS). The researchers originally identified several regions, rather than single genes, of the genetic code that were strongly associated with autoimmunity.
Since then, GWAS have found hundreds of regions of the genome involved in various autoimmune diseases. These mutations typically have small individual effects. But, in considering their polygenic effect, their collective contribution to autoimmunity risk is significant.
It is possible that some of your genes may be tested during your clinical journey. However, at this point, genetic testing is uncommon outside of clinical trials. It is much more likely that a doctor would consider any known family history of autoimmunity when approaching a diagnosis.
Which autoimmune diseases most often run in families?
Authorities in autoimmunity categorize between 80 and 100 different illnesses as autoimmune diseases.
In some families, there are clusters of the same autoimmune conditions. In this case, members of the family have been diagnosed with the same condition. Alternatively, other families have clusters of autoimmunity, but with different autoimmune disease types. So, a family like this would have various autoimmune diseases.
The following diseases are known to cluster in families (with either the same or different autoimmune diseases):
- Rheumatoid arthritis (RA)
- Systemic lupus erythematosus (lupus)
- Multiple sclerosis (MS)
- Autoimmune thyroid disease (Grave’s disease or Hashimoto’s thyroiditis)
- Type 1 Diabetes
As an example, lupus and RA may run in your family, and you may be diagnosed with Hashimoto’s thyroiditis.
Does having a family member with autoimmunity increase your likelihood of having an autoimmune disease?
Genetic and environmental risk profiles may inform whether or not there is a cluster of autoimmunity within a family. Current research indicates that approximately 30% of the risk of developing an autoimmune disease is due to hereditary factors.
Separate autoimmune diseases affect different areas of the body and may require different specialists or treatments. But, if autoimmunity is in your family, the reason why you may have developed an autoimmune disease may be the same.
Family members may share similar genetic predispositions. They may have been exposed to similar environmental toxins or stressful experiences that triggered autoimmune diseases or symptoms.
Often, people are unaware that their disease or the disease of a member of their family is considered an autoimmune disease. This lack of awareness could mean that people do not relay helpful information to their doctors.
To best inform your physician, try to find out the number and types of autoimmune diseases that run in your family.
Do genetics alone cause autoimmune disease?
Autoimmune diseases are not just caused by genetics. Instead, autoimmune diseases are considered to be caused by a combination of factors.
Importantly, while genetic risk may be present, genes must also interact with other factors from a person’s environment. Viruses, bacteria, lifestyle, metabolism, and nutritional health each play a role. Ultimately, the true risk of an individual developing an autoimmune disease is difficult to assess.
If autoimmune diseases were solely genetic then identical twins would be genetically programmed to develop the same diagnoses at relatively the same age. Yet, research contradicts this hypothesis.
In 2015, a Stanford University team concluded their trial on identical twins. Their research found that non-heritable influences, not genes, are the prime drivers of autoimmune disease susceptibility. More often, microbes, infections, and other physical and environmental factors (like hormones and chemicals) are to blame.
The nature versus nurture debate surrounding autoimmunity has been long-standing. But, science confirms that it is not either nature or nurture that causes disease, but the interplay between the two.
We should all consider our genetic and familial inheritance and do our best to report important information to our doctors. However, the largest part of the development of autoimmune disease lies in our internal and external environments. Addressing our lifestyles, diets, exposures, and more can provide even greater insight into our immune health and long-term wellbeing.