MAPT and Alzheimer disease: The axon is susceptible to tau pathology in these neurodegenerative diseases, with evidence of white matter changes indicative of axonal degeneration in tauopathies such as Alzheimer’s disease.1‐3 Studies in animal models have demonstrated that axonal dysfunction in tauopathy is typified by disrupted axonal transport,4‐6 due to tau hyperphosphorylation resulting in reduced cytoskeletal integrity.7 Additionally, axonal swellings and loss of white matter, hallmarks of axonal degeneration have been observed in P301L-tau mice, a model of familial frontotemporal dementia.8‐10