MAPT and juvenile Huntington disease: Unlike classical neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and ALS, which are prominently defined by the accumulation of misfolded and aggregated proteins (such as amyloid-β, tau, α-synuclein, TDP-43, or mutant huntingtin), MS is not driven by pathological protein aggregation.