Restless Leg Syndrome (RLS) is a neurological condition defined by an urge to move the legs. This urge is often accompanied by uncomfortable sensations described as pulling, throbbing, or crawling deep within the limbs. These feelings emerge during periods of rest or inactivity, such as sitting down or trying to fall asleep, and are temporarily relieved by movement. For those with these symptoms, a common question is what causes the condition and if there is a family connection.
The Evidence for a Genetic Link
A person’s genetic makeup can play a large part in the development of RLS, as studies show the condition often appears in multiple generations. Between 40 and 90 percent of individuals with RLS report having at least one first-degree relative, like a parent or sibling, who also has the disorder. This pattern suggests a strong hereditary component, known as familial RLS.
Further evidence comes from studies involving twins. Research has shown that identical twins, who share nearly all of their DNA, have a higher concordance rate for RLS than non-identical twins. This means that if one identical twin has RLS, the other is much more likely to have it as well. The connection is particularly strong in cases where symptoms begin earlier in life.
Identifying Hereditary RLS vs. Other Causes
RLS is classified into two main types: primary and secondary. Primary RLS, also called idiopathic RLS, is the form most strongly linked to genetics where the condition is not caused by another medical issue. This type is often associated with an earlier onset of symptoms, typically before the age of 45.
Secondary RLS develops as a result of another medical condition or as a side effect of certain medications. A common trigger is iron deficiency, as the brain uses iron to produce dopamine, a chemical messenger involved in controlling movement. Other conditions associated with secondary RLS include end-stage kidney disease, diabetes, multiple sclerosis, and Parkinson’s disease. It can also arise during pregnancy.
Inheritance Patterns and Associated Genes
In many families where RLS is passed down, the condition appears to follow an autosomal dominant inheritance pattern. This means that inheriting just one copy of an altered gene from a single parent is enough to increase a person’s risk of developing the disorder. A parent with this gene has a 50% chance of passing it on to each child, which explains why the condition is seen in every generation of affected families.
Genetic analyses have pinpointed several specific gene variants that are more common in people with RLS. Among the most consistently identified are variations in genes known as MEIS1, BTBD9, and TOX3. While the exact functions of these genes in relation to RLS are still being investigated, their discovery confirms that genetic factors contribute to a person’s susceptibility to the condition.
Implications for Diagnosis and Family Members
Understanding the genetic component of RLS has practical implications for diagnosis. Because there is no single laboratory test for primary RLS, a detailed family health history becomes a valuable tool for physicians. Learning that a patient has relatives with similar symptoms can help a doctor confirm a diagnosis more confidently.
Relatives of someone with familial RLS have an increased likelihood of developing the condition themselves. However, inheriting a gene variant does not guarantee that a person will experience symptoms. This concept, known as incomplete penetrance, means that other genetic and environmental factors are also at play. Currently, genetic testing for RLS is not a standard part of the diagnostic process and is used mostly in research settings.