ALS is directly hereditary in only 10 percent of families. The vast majority of ALS cases are sporadic, meaning that although there is likely a genetic predisposition involved, ALS is not directly inherited in a family.

Although there is a genetic test for ALS, it is still quite limited. In 20 percent of families with inherited ALS, a change in the gene called SOD1 on chromosome 21 has been found, however, 80 percent of families with inherited ALS do not show a change in their SOD1 gene.

Scientists are diligently looking for other genes that may be involved in ALS, but currently, there is no other genetic test that will identify ALS in families. Therefore, the determination that an individual has the inherited type of ALS is typically based on family history rather than a genetic test.

If you have some symptoms of ALS and there is someone in your family that has had ALS, such as a parent, grandparent, aunt, uncle, or brother or sister, you may wish to undergo genetic testing.

Keep in mind, however, that the SOD1 gene mutation will be present in only about 20 percent of families with ALS, and that in the other 80 percent of families there are still other unidentified genes that cause ALS.

A positive test means that the genetic cause of ALS has been identified, whereas a negative test means that ALS may still be present in families, but the gene is unidentified.

Some people may wish to be tested if there is someone in their family with ALS, even if they themselves do not show any neurological symptoms. This is called "presymptomatic testing", and can only be done if the family member that has ALS has the mutation in the SOD1 gene. If the family member with ALS does not have this gene, testing cannot be done, since it is an unidentified gene that is causing the ALS.

Also, it is important to know that even if you are diagnosed with the mutated SOD1 gene, this does not mean that you will automatically and definitely get ALS; however, if you do carry the gene, you may wish to use this knowledge to make important lifestyle changes, which may help to defer or even prevent the onset of the disease.

It may be wise to start following some of the ALS dietary and supplementary suggestions that have been put forward by various professionals, many of which can be found on this web site.