Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. These nerve cells, called motor neurons, control voluntary muscle movement. As motor neurons degenerate and die, they stop sending messages to muscles, leading to loss of muscle control. This progressive loss impacts a person’s ability to speak, eat, move, and breathe over time.
How ALS Is Inherited
ALS has two main forms: sporadic ALS (SALS) and familial ALS (FALS). Sporadic ALS accounts for about 90-95% of cases, with no known family history. For SALS, the risk of a child inheriting ALS from a parent is not increased beyond the general population.
Familial ALS accounts for about 5-10% of cases and involves a known family history. This form implies an inherited genetic component. If a parent has FALS, the likelihood of inheriting the genetic predisposition can be higher, often around 50% for autosomal dominant patterns. However, inheriting the genetic mutation does not guarantee the development of the disease, as penetrance can vary.
Genetic Testing and Counseling
Several genes contribute to familial ALS. The most frequently associated genes include C9orf72, SOD1, TARDBP, and FUS. These account for a significant portion of inherited cases, though others are also under investigation.
Genetic testing analyzes DNA for mutations in these genes. It is considered for individuals with a strong family history, especially multiple affected relatives across generations. Results indicate if an individual carries a gene mutation linked to familial ALS.
Genetic counseling provides individuals and families with information and support. A genetic counselor helps interpret test results, explaining the implications of a positive, negative, or uncertain finding. Counselors also discuss ethical and psychological considerations of knowing one’s genetic status, particularly regarding pre-symptomatic testing.
Beyond Genetics: Other Influences and Coping
While genetics influence familial ALS, research suggests ALS development, even in sporadic cases, involves genetic predispositions and environmental factors. Scientists study environmental exposures and lifestyle elements that might contribute to ALS development, though no definitive environmental causes have been established. This ongoing research aims to understand the full spectrum of influences beyond direct genetic inheritance.
Uncertainty from a familial ALS history can be emotionally challenging. Focusing on well-being, rather than dwelling on future outcomes, is a supportive approach. Engaging in mental health activities, such as connecting with support groups or seeking individual counseling, provides coping mechanisms. Managing the emotional impact involves acknowledging feelings, seeking information from reliable sources, and concentrating on present health and quality of life.