Partly. Autoimmune diseases tend to run in families, and certain inherited genes make the immune system more likely to turn on the body. But for nearly everyone, genes only load the dice: something in a person’s life, or plain chance, usually decides whether disease ever starts.1PubMed Central. Viral triggers for autoimmunity What gets inherited is often a general tendency toward autoimmunity rather than one specific disease, so a single family can carry several different conditions.
What Your Family History Means for Your Risk
Closeness of the relationship matters. A sibling of someone with lupus is about 24 times as likely to get lupus as someone with no affected family.2PubMed. Familial Aggregation of Systemic Lupus Erythematosus and Coaggregation of Autoimmune Diseases in Affected Families Parents and children of someone with lupus are about 11 to 14 times as likely.3PubMed. Familial Aggregation of Systemic Lupus Erythematosus and Coaggregation of Autoimmune Diseases in Affected Families Those are big multipliers, but lupus is uncommon to begin with, so even a much higher risk leaves most relatives unaffected. Spouses, who share no genes, are still about 4 times as likely, a hint that shared homes and habits matter too.4PubMed. Familial Aggregation of Systemic Lupus Erythematosus and Coaggregation of Autoimmune Diseases in Affected Families
“Times as likely” multiplies a small starting chance; it is not a coin flip. The same multiplier means more for a common condition like thyroid disease, because a modest multiple of a higher baseline gives a much larger absolute chance. These figures come from studies of whole groups, so they describe how families compare on average and cannot say what will happen to one person. The useful question for your doctor is the baseline rate of that specific disease for someone of your age and sex, since that is the number your multiplier applies to.
Families also share different diseases, not just the same one. Having a parent, sibling or child with lupus raises the chance of other conditions, such as Sjögren syndrome about 6 times and rheumatoid arthritis about 2.7 times.5PubMed. Familial Aggregation of Systemic Lupus Erythematosus and Coaggregation of Autoimmune Diseases in Affected Families Relatives of people with thyroid autoimmune disease, type 1 diabetes, rheumatoid arthritis or MS carry a 1.3 to 2.4 times higher risk of some autoimmune disease.6PubMed Central. How do autoimmune diseases cluster in families? A systematic review and meta-analysis
A mother with thyroid disease, a sister with celiac disease and a cousin with psoriasis can together be one family pattern, even though no two relatives share a diagnosis. So a family history of any autoimmune condition is worth mentioning to your doctor, even if your own symptoms look different. Writing down each relative’s diagnosis and the age it started gives your doctor something concrete to work from, and vague labels like “a thyroid problem” are worth confirming with the relative. If you come from such a family and have unexplained tiredness, rashes or joint pain, it is reasonable to raise it sooner rather than waiting to see if it passes.
How Much Is Genes and How Much Is Everything Else
Identical twins are a natural experiment. They share all their genes, so if genes alone decided autoimmune disease, both twins would always get it. Yet often only one develops the disease, which shows other causes are at work.7PubMed. Twin studies in autoimmune disease: genetics, gender and environment Still, an identical twin of someone with lupus is about 316 times as likely to have lupus as the general population.8PubMed. Familial Aggregation of Systemic Lupus Erythematosus and Coaggregation of Autoimmune Diseases in Affected Families
Identical twins share their genes but not their lives. They may meet different infections, work in different jobs, eat differently or differ in whether they smoke. Chemical tags that switch genes on and off can differ between identical twins.9PubMed Central. Epigenetics of discordant monozygotic twins: implications for disease The chemical switches that turn genes up or down keep changing over a lifetime, and some of those changes can reverse. Chance also plays a part, because the immune system builds its recognition cells through random shuffling, so even identical genes can produce different collections of immune cells.
The genetic share differs from disease to disease. Celiac disease and psoriasis are among the most strongly genetic autoimmune conditions, while in rheumatoid arthritis and systemic sclerosis genes play a more limited role.10PubMed. Lessons learned from twins in autoimmune and chronic inflammatory diseases MS often strikes only one of two identical twins.11PubMed Central. DNA methylation signatures of monozygotic twins clinically discordant for multiple sclerosis
For autoimmune disease, “genetic” usually means many small gene effects added together. Most autoimmune disease shows up in people with no clear family history.
The Genes Behind Autoimmune Risk
The biggest cluster of risk genes is the HLA genes, the instructions the immune system uses to tell the body’s own cells from invaders. This gene region is linked to hundreds of diseases, including autoimmune ones.12Journal of Bio-X Research. The human leukocyte antigen and genetic susceptibility in human diseases Some versions make it easier for the immune system to misread your own tissue as foreign. One version of these genes raises autoimmune risk about 2 times.13PubMed. Exploring the role of genetic variants in susceptibility to autoimmune Diseases: A molecular genetics approach
A risk gene that doubles your odds is a nudge, not a cause. Many healthy people carry these variants, which is why finding one in yourself says little by itself. Risk builds when several variants combine with triggers such as infections or smoking.
Many risk genes are shared across diseases. Outside the HLA region, a gene called PTPN22 raises risk for lupus, vasculitis and other autoimmune diseases.14PubMed Central. PTPN22: the archetypal non-HLA autoimmunity gene One common PTPN22 variant raises risk about 1.8 times.15PubMed. Exploring the role of genetic variants in susceptibility to autoimmune Diseases: A molecular genetics approach Roughly half of the gene regions linked to two or more autoimmune diseases act the same way in each.16PubMed Central. Common genetic factors among autoimmune diseases That is how one inherited tendency can show up as lupus in one relative and arthritis in another.
When a Single Gene Is the Cause
Autoimmune diseases caused by a single faulty gene are rare.17PubMed Central. Monogenic Autoimmune Diseases: Insights into Self-Tolerance One example, APECED, comes from a broken AIRE gene that normally teaches young immune cells to ignore the body’s own tissues.18PubMed. Genetic basis of altered central tolerance and autoimmune diseases: a lesson from AIRE mutations Single-gene forms of hormone-gland autoimmunity usually start younger than common forms.19PubMed. Monogenic autoimmune diseases of the endocrine system Even with the same mutation, family members can be affected very differently.20PubMed. Monogenic autoimmune diseases of the endocrine system Childhood onset plus several autoimmune conditions or unusual features is when doctors consider genetic testing.21PubMed. Monogenic autoimmune diseases of the endocrine system
Unusual extras, such as repeated yeast infections alongside hormone-gland problems, are one clue. A common adult-onset disease in a few relatives usually fits the many-small-genes pattern instead, and is not a reason to suspect a single-gene cause. If the childhood signs do appear, a referral to a genetics service is the usual route to testing and counselling.
Why Women Get Autoimmune Diseases More Often
Women have two X chromosomes, and one is normally switched off in every cell. One immune gene can escape that shutdown in some immune cells of women.22PubMed Central. The Inactive X Chromosome: A Genetic Driver of Female‐Biased Rheumatic Autoimmune Disorders? Those cells then react more strongly to signals that drive antibody-making cells.23PubMed Central. The Inactive X Chromosome: A Genetic Driver of Female‐Biased Rheumatic Autoimmune Disorders? Men with an extra X, as in Klinefelter syndrome, show the same escape.24PubMed Central. The Inactive X Chromosome: A Genetic Driver of Female‐Biased Rheumatic Autoimmune Disorders? In female mice, loosening the X shutdown caused lupus-like disease on its own.25PubMed Central. Altered X-chromosome inactivation predisposes to autoimmunity Hormones and pregnancy also shape immune activity, so genes are only part of the female bias.
Can a Genetic Test Tell You If You Will Get One
Celiac gene tests are good at ruling the disease out. Almost everyone with celiac disease carries one of two gene types, called HLA-DQ2 and HLA-DQ8, so testing negative for both nearly rules celiac disease out.26PubMed. Accuracy of serologic tests and HLA-DQ typing for diagnosing celiac disease The catch is that about 4 in 10 people checked for celiac without having it also carried one of these genes.27secure.arkansasbluecross.com. Genetic Test: Celiac Disease, HLA Typing (HLA-DQ) A positive result only says celiac is possible; in one group only about 1 in 13 positives had the disease.28secure.arkansasbluecross.com. Genetic Test: Celiac Disease, HLA Typing (HLA-DQ)
That makes the test useful if you are already eating gluten-free and cannot do standard blood tests, because those need gluten in your diet to work. It can also help relatives of someone with celiac decide whether repeat screening is needed, since a negative result means they can likely stop worrying. A positive result changes little by itself, so if symptoms appear you still need antibody blood tests.
Combined gene scores are mainly a specialist tool. A polygenic risk score adds many small gene effects into one number.29PubMed. A polygenic risk score to help discriminate primary adrenal insufficiency of different etiologies Such scores helped doctors spot children whose adrenal disease had a single-gene cause and was misdiagnosed.30PubMed. A polygenic risk score to help discriminate primary adrenal insufficiency of different etiologies For most people, consumer gene results showing “raised risk” are not a diagnosis. The flagged variants are common and usually harmless alone, and they don’t account for environment or the other genes you carry. Bring a home DNA report to a doctor rather than acting on it.
What Turns a Genetic Risk Into Disease
Smoking is the clearest example for rheumatoid arthritis. Carrying a risk gene version without smoking raises risk about 2.8 times, and smoking without the gene raises it about 2.4 times.31PubMed. A gene-environment interaction between smoking and shared epitope genes in HLA-DR provides a high risk of seropositive rheumatoid arthritis Smokers with the gene face about 7.5 times the risk, and about 16 times with two copies.32PubMed. A gene-environment interaction between smoking and shared epitope genes in HLA-DR provides a high risk of seropositive rheumatoid arthritis If rheumatoid arthritis runs in your family, not smoking is one of the most useful protective steps.
Infections and gut bacteria can also act as triggers. Some viruses and bacteria look enough like body tissue that the immune response can spill onto self, though this only causes disease when the body’s usual safeguards also fail.33PubMed Central. Viral triggers for autoimmunity HLA risk genes are linked to different gut bacteria in infants.34PubMed Central. Genetic risk for autoimmunity is associated with distinct changes in the human gut microbiome In mice, genes and gut bacteria together set the risk of nervous-system autoimmunity.35PubMed Central. Interactions between host genetics and gut microbiota determine susceptibility to CNS autoimmunity
If autoimmune disease runs in your family, keep vaccinations current and have infections treated promptly. Learn the early symptoms of the diseases in your family so you can raise them early. Ask your doctor whether screening such as thyroid or celiac blood tests makes sense for you.
How Genes Can Shape Treatment
Azathioprine, an immune-calming drug, can be dangerous for people with certain TPMT or NUDT15 gene variants.36PubMed Central. Precision Medicine for Rheumatologists: Lessons from the Pharmacogenomics of Azathioprine US drug labels include guidance for these variants, and people with two non-working copies are advised not to take it for non-cancer conditions.37PubMed Central. Precision Medicine for Rheumatologists: Lessons from the Pharmacogenomics of Azathioprine If azathioprine is on the table, ask whether TPMT and NUDT15 testing is needed before starting.
The test is usually a simple blood or cheek-swab sample, and results may lead to a lower dose or a different drug. Using genes to predict which drug will work best is still developing.