Abnormal tau-reactive filaments in olfactory mucosa in biopsy specimens of patients with probable Alzheimer's disease.

We immunocytochemically analyzed pieces of olfactory mucosa removed by biopsy in 8 patients with probable Alzheimer's disease (AD) and 6 age-matched controls, with tau and ubiquitin antisera. There were tau-reactive and, partially, ubiquitin-reactive dystrophic neurites in the lamina propria of olfactory mucosa in all AD cases. The tau-reactive neurites contained abnormal straight filaments, 15 to 18 nm in diameter, morphologically identical to those found in AD cerebral brain tissue obtained at autopsy. Tau and ubiquitin immunoreactivity were absent in controls. If these neuritic alterations are confirmed in a larger number of cases, analysis of olfactory mucosa may increase the current reliability of clinical diagnosis of AD.