We similarly have observed patients presenting with a progressive dysexecutive syndrome from a wide variety of aetiologies, including GRN mutation carriers as described by Tábuas-Pereira et al. In our experience, we have found that the parietofrontal hypometabolism observed in these GRN cases is strikingly asymmetric in comparison to the hypometabolism observed in sporadic Alzheimer’s disease cases with the same clinical syndrome. The gene discussed is GRN; the disease is Alzheimer disease.