What goes wrong in lou gehrig's disease?

NOT fully clear. We do know it is a disease which results in loss of motor nerve cells in brain and spinal cord, and there is an incidence of 10% familial involvement. Rarely, there is a mutation in gene encoding of copper/zinc superoxide dismutase, but otherwise, we are not clear as to what is causing this devastating condition.
Nerve cell death. Nerve celles that produce movement begin to die causing weakness that affects the arms and legs and eventually the muscles that control swallow and speech.