Can alzheimer's usually run in the family?

Usually not genetic: Most of the time Alzheimer's disease does not run in families. There are a few genes where if you have the gene, you get the disease, but these are extremely, extremely rare. There are susceptibility genes as well. Most of the time when it runs in families, it is not a surprise, as many members have it, and it is usually at a much younger (i.e. 40s, low 50s) age.