Overall, p-MAPT staining was sparse in the fornix in cases with entorhinal neurofibrillary degeneration and there was no significant difference in fornix p-MAPT axonal staining between the 12 brains with B1 Alzheimer disease neuropathologic changes (8.7 ± 2.6 p-MAPT-positive axonal profiles) and the seven brains with possible Braak stage I-II PART (5.7 ± 2.2 p-MAPT-positive axonal profiles). The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.