What is lou gehrig disease caused by?

Most are sporadic: While most cases of lou gehrigs disease do not have a known cause ("sporadic als"), approximately 5% of cases do run in families ("familial als"). There have been many proposed risk factors for developing sporadic als, but no clear smoking gun has been found to date.

Do not know cause: A small percentage of cases are genetic or associated with frontotemporal dementias. Sporadic ALS is a disease associated with a misfolded protein, cooper/zinc superoxide dysmutase, but not fully clear why this happens, the drug Riluzole may be a clue, as it affects glutamate, and maybe here is one possible pathway for investigation.