The exact cause of ALS is not yet known, but researchers are constantly learning more about the disease. In the vast majority of the cases-somewhere between 90 to 95 percent-there is no known cause, and is deemed as being sporadic ALS.
In the remaining 5 to 10 percent of cases, the disease is called familial ALS because it is passed down through families. A child born to someone with familial ALS has a 50-50 chance of getting the disease, as well.
In 1993, researchers made a huge breakthrough regarding the gene responsible for familial ALS. They discovered a change, or mutation, in a gene called superoxide dismutase (SOD1), which is the gene responsible for familial ALS.
When the gene is normal, it protects the motor neurons from by damage by directing the production of an enzyme to guard against free radicals. When the gene is mutated, however, the enzyme is unable to protect the motor neurons, which then are vulnerable to the free radicals.
An estimated 20 percent of the people who have familial ALS also have the SOD1 gene mutation. Researchers continue to search for other genes that might be involved.
Researchers think some other possible causes for ALS might include:
• An autoimmune response, in which the body attacks its motor neurons by mistake
• An exposure to viruses or toxic substances
• An abnormality of the immune system that leads to inflammation in the spinal cord and the brain
• A diet lacking in certain nutrients
However, there is a lack of scientific evidence to prove any of these theories.
More Answers from Discovery Health