As CSF brassicasterol levels have been reported to be reduced in AD patients and to improve the predictive power of CSF Aβ and tau levels as AD biomarkers, it will be of interest to determine whether serum and CSF brassicaterol levels are reduced in DS subjects throughout their lifespan or could be used as a prognostic biomarker of incipient AD neuropathology in DS subjects. The gene discussed is MAPT; the disease is Dravet syndrome.