Alzheimer’s disease affects about 30% of adults above the age of 85. Scientists have identified many common genetic variants that contribute to the disease and are now searching for rare mutations with significant effects in the population. In this study scientists focus on the U.S. and Europe to analyze more than 11,000 genes in 1,393 late-onset Alzheimer’s disease patients. They identify a variant in the TM2D3 gene that is associated with both a higher risk and earlier age of onset of Alzheimer’s disease. The TM2D3 genetic variant is about 10 times more common in Icelanders compared to the European population in general.