How can I tell if I have a hereditary form of ALS?

Familial ALS means that ALS has a genetic cause that can be passed down within a family (known as “familial ALS,” or FALS). The familial form of ALS is identified when more than one family member develops the disease.

A typical scenario is one in which—in addition to the patient—a case of ALS is already known to have occurred in the father, mother, an uncle or aunt, or among the grandparents or siblings. It is less common for siblings to develop the disease without a history of ALS or frontotemporal dementia (which is genetically linked to ALS) in previous generations. The family tree and the diseases associated with family members (family medical history) provide crucial clues regarding the presence of hereditary ALS.

The results of genetic testing (mutation detection) provide molecular genetic evidence of the “hereditary factor.” Currently, a mutation can be detected in about 50% of all people with hereditary ALS.