Corticobasal Degeneration (CBD) is a rare, progressive neurodegenerative disorder impacting the brain. Many wonder if such conditions are hereditary. This article clarifies the hereditary aspects of CBD.
What is Corticobasal Degeneration
CBD is a neurological condition where brain cells degenerate and die. It specifically affects regions like the cerebral cortex, which handles memory and voluntary movements, and the basal ganglia, important for motor control. A hallmark of CBD is the abnormal accumulation of tau protein within brain cells. These tau protein clumps, known as neurofibrillary tangles, contribute to brain cell damage and death.
Is CBD Inherited
The vast majority of Corticobasal Degeneration cases are “sporadic,” meaning they occur without a clear family history. However, rare familial forms of CBD do exist, where the condition can run in families.
These uncommon inherited cases are typically linked to specific genetic changes. For example, mutations in the MAPT gene, which provides instructions for making the tau protein, have been identified in some families. Other genes like GRN and C9ORF72 are also associated with familial forms of corticobasal syndrome. These familial forms represent a very small percentage of all CBD diagnoses.
Genetic Influences Beyond Direct Inheritance
Even when Corticobasal Degeneration is not directly inherited, genetic factors can still influence an individual’s susceptibility to the condition. Certain genetic variations, often referred to as risk factors, can increase a person’s predisposition to developing neurodegenerative diseases like CBD. These genetic predispositions do not guarantee that someone will develop the disease, but they can make it more likely.
A notable example is the H1 haplotype of the MAPT gene, which is a strong genetic risk factor for sporadic CBD. This specific genetic pattern is more common in individuals with CBD compared to the general population. Conversely, the H2 haplotype of the MAPT gene is associated with a decreased risk of CBD. It is important to note that many people carry the H1 haplotype without ever developing CBD, highlighting that it is a risk factor, not a direct cause.
Understanding Genetic Information for Families
Given that most cases of Corticobasal Degeneration are sporadic, the risk for other family members to develop the condition is generally very low. This can provide reassurance to families where a loved one has been diagnosed with the sporadic form of CBD. For families with a known, rare familial form of CBD, genetic counseling can offer valuable insights.
Genetic counseling helps families understand inheritance patterns and assess potential risks for future generations. Genetic testing may be considered in these specific situations, especially when there is a strong family history suggestive of an inherited neurodegenerative disorder. Such testing assists in clarifying the genetic basis of the disease within that particular family, guiding discussions about potential implications.