MAPT and Alzheimer disease: If MAPT were mosaically altered in SAD brains, but perhaps in different cells or brain regions, it might contribute to AD progression, and importantly, explain the high co-morbidity between AD and PD/other proteinopathies (Kovacs et al., 2013; Brenowitz et al., 2017; Kapasi et al., 2017); further study is warranted.