genetic factors in ad development

Two types of AD have been
identified: familial AD (FAD), which follows an inheritance pattern, and
sporadic AD. The Diagnostic and Statistical Manual of Mental Disorders (4th
ed., 1994, DSM-IV) describes AD as early-onset (younger than sixty-five
years) or late-onset (sixty-five years and older). Only 5 to 10 percent of AD
cases are early onset. Some forms of early-onset AD are inherited and often
progress faster than late-onset AD.