The Alzheimer amyloid protein precursor (APP) is subject to proteolysis by ADAM10 and ADAM17, precluding the formation of A?. Recently, coding variations in ADAM10 resulting in altered function have been reported in familial Alzheimer disease (AD). The authors carried out a large-scale (n = 576: Controls, 271; AD, 305) resequencing study of ADAM10 in sporadic AD. The results do not support a significant role for ADAM10 mutations in AD. The results also make it clear that the careful examination of ancestry required in any case-control comparison is especially true with rare variations, where even a very small number of variations might form the basis of scientific conclusions.