If someone in your family has been diagnosed with Lewy body dementia, it is natural to wonder whether you or your children are at risk. The short answer: in the large majority of cases, Lewy body dementia is not inherited. Most people who develop it have no family history of the disease. A small minority of cases do run in families, and researchers have identified a handful of genes linked to higher risk. But for most families, genetics is not the main driver.
That distinction matters. It separates the rare inherited forms from the far more common sporadic form, and it shapes what genetic testing can and cannot tell you.
What Is Lewy Body Dementia?
Lewy body dementia is a progressive brain disorder caused by abnormal clumps of a protein called alpha-synuclein inside brain cells. These clumps are called Lewy bodies. They damage the brain regions involved in thinking, movement, behavior, and sleep regulation.
It is one of the most common forms of dementia, though estimates of how common vary. It sits alongside Alzheimer’s disease and vascular dementia as a leading cause. The condition has two related presentations that clinicians often group together: dementia with Lewy bodies and Parkinson’s disease dementia. Both involve Lewy bodies. The difference is largely about timing. In dementia with Lewy bodies, cognitive symptoms appear first or within about a year of movement symptoms. In Parkinson’s disease dementia, the movement symptoms of Parkinson’s have usually been present for years before dementia develops.
This overlap is one reason the genetics are complicated. The underlying protein problem is similar, but the way it plays out differs from person to person.
Is Lewy Body Dementia Hereditary?
No, Lewy body dementia is not hereditary in the way some conditions clearly are. The vast majority of cases are sporadic, meaning they occur without any clear family pattern.
When researchers study families, they find that having a relative with Lewy body dementia raises risk only modestly for most people. That is different from conditions caused by a single dominant gene, where a parent with the mutation passes it on with a predictable chance. Lewy body dementia does not behave that way in most cases.
That said, “not hereditary” does not mean “no genetic component at all.” Genetics can influence risk without directly causing the disease. Think of it as one factor among several, not a switch that is flipped.
When Does Lewy Body Dementia Run in Families?
In a small number of families, Lewy body dementia does appear to be inherited. These cases tend to stand out. They often involve multiple relatives across generations, an earlier age of onset, or a pattern that looks dominant.
Researchers have linked some of these rare familial cases to specific gene mutations. The most studied involve the SNCA gene, which provides instructions for making alpha-synuclein. Rare mutations in this gene can cause abnormal protein buildup and are associated with inherited forms of Lewy body disease and related conditions. Other genes, including LRRK2 and GBA, have been linked to Parkinson’s disease and, in some cases, to Lewy body dementia risk.
These inherited forms are uncommon. They represent a small slice of all Lewy body dementia cases. If a family has several affected members, that is a signal worth discussing with a doctor or genetic counselor, but it is not the typical picture.
What Role Do Genes Play in Sporadic Lewy Body Dementia?
Even in cases with no family history, genes still matter. Certain genetic variants are more common in people who develop the disease than in those who do not.
The APOE gene is one example. A particular version of it, known as APOE e4, is a well-established risk factor for Alzheimer’s disease. Its relationship to Lewy body dementia is less clear. Some studies suggest it may also raise risk, but the evidence is not as strong or as consistent as it is for Alzheimer’s.
The GBA gene is another. Variants in this gene are among the most common genetic risk factors for Parkinson’s disease, and some research indicates they also appear more often in people with Lewy body dementia. These variants do not cause the disease on their own. They increase susceptibility.
This is the key concept: risk genes are not destiny. They tilt the odds. Many people with these variants never develop dementia, and many people without them do.
What Other Factors Contribute to Lewy Body Dementia?
Genetics is only part of the story. Age is the strongest known risk factor. Lewy body dementia becomes more common as people get older, and most diagnoses occur after age 60.
Being male appears to raise risk somewhat, though the reasons are not fully understood. Some research points to additional factors, but the evidence varies. Unlike Alzheimer’s disease, where factors like cardiovascular health and lifestyle have been studied extensively, the research on modifiable risk factors for Lewy body dementia is more limited.
What is clear is that this is a complex condition. No single cause explains most cases. It likely arises from a mix of age, genetics, and other influences that researchers are still working to identify.
Should You Get Genetic Testing for Lewy Body Dementia?
For most people, genetic testing is not recommended. There is no single gene test that can tell you whether you will develop Lewy body dementia, and the risk genes identified so far do not provide clear, actionable answers for the general population.
Testing may be considered in specific situations. These include a strong family history with multiple affected relatives, an unusually early age of onset, or a pattern that suggests an inherited form. In those cases, a genetic counselor can help weigh the benefits and limits of testing.
It is worth being direct about what testing can and cannot do. Even when a risk variant is found, it usually cannot predict whether or when symptoms will appear. And a negative result does not guarantee you will not develop the disease. This is why testing is a decision to make with professional guidance, not something to pursue casually.
What Does This Mean for Families?
For most families, the message is reassuring in a measured way. Having one relative with Lewy body dementia does not mean you will develop it. The disease is not passed down in a simple, predictable pattern for the majority of people.
At the same time, it is honest to acknowledge that family history does carry some weight. If you have a parent or sibling with the condition, your risk may be somewhat higher than average. That is worth mentioning to your doctor, especially as you get older.
If you are concerned about a strong family pattern, a conversation with a genetic counselor or neurologist can help clarify your situation. They can review your family history and explain whether testing or other steps make sense.
What you should not do is assume the worst from a single family diagnosis, or assume you are completely in the clear. The reality sits in between, and it depends on your specific circumstances.
Frequently Asked Questions
Is Lewy body dementia hereditary?
In most cases, no. The large majority of Lewy body dementia cases are sporadic and occur without a clear family pattern, though a small number of inherited forms exist.
Can Lewy body dementia skip a generation?
It can appear to, but this is not because of a predictable inheritance pattern in most cases. Sporadic cases occur without any clear generational link, so a family may see it in one generation and not the next.
What genes are linked to Lewy body dementia?
Rare mutations in the SNCA gene are linked to inherited forms, while variants in GBA and LRRK2 are associated with higher risk. The APOE e4 variant may also play a role, though the evidence is less consistent.
Should I get tested if a parent had Lewy body dementia?
Not routinely. Testing is generally considered only when there is a strong family history or an unusually early onset, and it should be done with guidance from a genetic counselor.
