Indeed, in skin samples of dogs suffering from AD, CB1 and CB2 immunoreactivity [291], as well as levels of PEA [228] were shown to be higher than in skin samples of healthy animals, and not less than 18 genetic variants of PTPN22 were shown to be likely to be associated with AD in West Highland white terriers [292]. This evidence concerns the gene PTPN22 and Alzheimer disease.