Based on a serum biomarker analysis, Thijs et al. divided adult AD patients into four distinct clusters: the patients in cluster 1 were characterized by symptoms with high levels of severity, the involvement of large body surfaces and the highest levels of the pulmonary and activation-regulated chemokine (PARC/CCL18), tissue MP1 inhibitor and soluble CD14 antigen. Here, CCL18 is linked to Alzheimer disease.