There are no ways to tell the difference between sporadic and familial ALS in terms of symptoms. Two patients with either sporadic or familial ALS will both go to their doctor with complaints of weakness and fatigue in a certain area of the body.
However, the same cannot be said of Guamanian ALS. There is a noticeable difference in the clinical symptoms of this form of ALS compared to the others. Patients diagnosed with Guamanian ALS will have symptoms of the Parkinson-Dementia Complex with the tremors characteristic of Parkinson's patients, and the memory loss that is commonly seen in Alzheimer's patients. Since the 1960s, the incidence of Guamanian ALS has dropped to worldwide levels.