familial form

[dana]

How do you know if you have the familial form of ALS? I know that it only happens in 5-10% of cases, but how do you officially find out? My dad was diagnosed with Lymes, but they have not ruled out ALS either. No one else in our family history has ever had ALS that we know of, but I wonder if this is something that we need to worry about or not.
Just curious,
Dana