AbstractBackgroundThe IVS10+14 microtubule‐associated protein tau gene (MAPT) mutation causes dysregulated protein splicing of MAPT, resulting in abnormal 4‐repeat isoform tau accumulation and associated with neurodegeneration. Three families expressing the IVS10+14 MAPT mutation have been reported who express the IVS10+14 MAPT mutation displaying a high degree of interfamilial heterogeneity in their clinical presentation. Herein, we describe the clinical and neuropathological presentation of a new Canadian cohort with this mutation.MethodClinical and neuropathological records, including neuropsychological and cognitive assessments, and stained neuropathological sections, were obtained for three family members with the IVS10+14 MAPT mutation. The records were reviewed and compared to previously reported families with this mutation.ResultThe Canadian cohort displayed many of the symptoms previously described in cases with the IVS10+14 MAPT mutation, including prominent motor, cognitive, behavioural, and behavioural symptoms. Additionally, consistent with the interfamilial heterogeneity described in literature, our cohort exhibited profound sensory and sleep abnormalities. Neuropathological information was available for two cases, in which one had widespread cortical and subcortical tau deposition and atrophy, while neuropathological changes in the other case was milder with the exception substantia nigral atrophy.ConclusionOur cohort demonstrate that while the IVS10+14 MAPT mutation often results in motor, cognitive and behavioural clinical features, sensory and sleep abnormalities are also manifestations of the mutation. Clinicopathological correlations were able to explain symptom presence and severity for two of the three examined cases. This underlines the need to explore alternate mechanisms and metrics of brain dysfunction in tauopathy in addition to tau burden and neuronal loss. Reference: Maxwell SP, Cash MK, Rockwood K, Fisk JD, Darvesh S. 2021. Clinical and Neuropathological Variability in the Rare IVS10+14 Tau Mutation. Neurobiology of Aging. In Press. DOI: 10.1016/j.neurobiolaging.2021.01.004.