Patients with Alzheimer disease (AD) often have Lewy body pathology (LBP). Although the exact significance of LBP is unknown, LBP appears to be more common in persons with familial AD related to gene mutations of presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid precursor protein. To examine the genetics of LBP, the team from Puget Sound HCS, led by James B. Leverenz, MD, associate professor at the University of Washington in Seattle, reviewed 25 familial AD cases that included 9 known PSEN1 mutations and 14 familial AD cases that included a single PSEN2 mutation. The brain stem, limbic cortex, and neocortex were examined for LBP.