Here, by examination of the endophenotypes ‘AD and asthma’ and ‘AD no asthma’ and by comparison of our results with those of existing GWAS for other related phenotypes, we have found that AD is determined by a combination of specific and shared effects, with the c11orf30-LRRC2 locus on chromosome 11 in particular showing effects on AD, asthma and AR. This evidence concerns the gene LRRC2 and Alzheimer disease.