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While type 1 diabetes (T1D) can run in families, most people who develop it don’t have a known family history. This article explores how genetics and the immune system play a role in risk, what autoantibody screening can reveal, and what parents and families should know about identifying risk early.
What does it mean when we say type 1 diabetes has a genetic component?
There is no single cause or single “type 1 diabetes gene.” T1D develops through a mix of genetic, immune and environmental factors. Some people inherit genes that make them more likely to develop T1D, but something in the environment (such as a viral infection or another immune trigger), is usually needed to start the process. More than 60 genes have been linked to increased risk, but none of them alone are enough to cause T1D, and it is still not fully understood what triggers its onset.
If type 1 diabetes runs in families, who specifically is at higher risk?
Having a close first or second-degree relative (for example, a sibling, parent, grandparent, aunt or uncle) with T1D increases risk, but it is still uncommon overall. In the general population, about 0.3% of people develop T1D, which is roughly three out of 1,000 people. For someone with a parent, sibling, or child with T1D, this risk increases to about 5%, or 50 out of 1,000. Fathers with T1D are slightly more likely to pass on risk than mothers. For second-degree relatives—such as grandparents, grandchildren, aunts, uncles, nieces or nephews—the risk is about 1%.
Even though family history increases risk, 80 to 90% of people diagnosed with T1D have no known family history, showing that other factors play a major role.
How can a child develop type 1 diabetes without any family history?
T1D is not directly inherited. It develops through a complex interaction between genes and environmental factors. Many different genes contribute to T1D risk, but having these genes does not mean someone will definitely develop T1D. A child can inherit a particular combination of these genes from both parents even if neither parent has T1D. These genes may make the immune system more likely to mistakenly attack the pancreas, but usually an environmental trigger, such as a viral infection or another unknown factor, is what starts this process. Because so many genes can influence risk, and environmental triggers are still not well understood, most people who develop T1D are the first in their families to have it.
What role does the immune system play in the development of type 1 diabetes?
The immune system plays a central role in the development of T1D. As an autoimmune condition, in T1D the body’s immune system mistakenly produces autoantibodies that attack its own insulin-producing cells in the pancreas. Antibodies are proteins made by the immune system to fight infections. However, in autoimmune diseases, the immune system mistakenly makes antibodies that target normal cells or tissues. This process starts long before any symptoms appear. The more types of diabetes autoantibodies someone has, the higher their risk of developing T1D
What are diabetes-related autoantibodies, and why are they important?
Normally, the immune system makes antibodies to protect the body from infections. In autoimmune diseases like T1D, however, the immune system mistakenly produces autoantibodies that target the body’s own cells. In T1D, four main types of autoantibodies attack the insulin-producing islet cells in the pancreas: insulin, glutamic acid decarboxylase 65 (GAD65), insulinoma antigen 2 (IA-2), and zinc transporter 8 (ZnT8). These autoantibodies contribute to the gradual loss of the pancreas’ ability to make insulin. They are important because they appear months to years before any symptoms or high blood sugar occur.
How is autoantibody screening used to identify type 1 diabetes risk?
Autoantibody screening involves a blood test that looks for one or more of the four diabetes-related autoantibodies in someone who does not yet have symptoms of diabetes. Finding these antibodies indicates a higher risk of developing T1D. The risk depends on the type and number of autoantibodies present, and the age at which they are detected. The risk of developing T1D increases with the number of autoantibodies found. People with multiple autoantibodies have more than a 90% chance of developing T1D, while those with only one autoantibody have a much lower risk and sometimes return to normal test results over time.
Should families with a child who has type 1 diabetes consider screening other siblings?
There can be benefits to screening siblings or other relatives of someone with T1D. Identifying higher risk before diabetes develops can allow time for education, help prevent serious complications such as diabetic ketoacidosis (DKA) at diagnosis, and may provide opportunities to take part in research or receive new treatments that could delay or prevent T1D.
However, screening can also cause emotional stress, as it involves regular follow-up and uncertainty about if or when T1D might develop. It is an important and personal decision that families should make with the support of their healthcare team or a diabetes specialist
What does a positive autoantibody test mean for a child’s future risk?
A positive autoantibody test does not mean a child will definitely develop T1D, but it does mean their risk is higher than average. The level of risk depends on how many autoantibodies are present, which ones are positive, and the child’s age and genetic background. Children who test positive for only one autoantibody have a low chance of developing T1D, especially if that autoantibody disappears within a few years. Doctors often recommend repeating the test once a year or two to see if additional antibodies have developed.
When two or more autoantibodies are present, the likelihood of developing T1D rises sharply. Children with multiple autoantibodies need closer follow-up, which may include periodic glucose testing and discussions about possible prevention or early-intervention studies. The younger the child is when these antibodies first appear, and the faster they accumulate, the higher the risk, so careful monitoring is especially important.
Can anything be done to delay or prevent type 1 diabetes in at-risk individuals?
There are many strategies being tested to delay or prevent type 1 diabetes. Health Canada recently granted Notice of Compliance (market authorization) for teplizumab, a medication that modifies the immune system to slow down its attack on insulin-producing cells. In clinical trials, teplizumab delayed the development of T1D by about two years on average in people who already had multiple autoantibodies and early signs of changes in blood sugar. Other medications that target the immune system are also being tested. In addition, researchers are studying cell-based therapies – such as using stem cells to create new insulin-producing cells or using specialized immune “regulatory” cells to reduce the immune attack – but these approaches are still experimental and not yet part of standard care.
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