Hyposmia in pure autonomic failure

Parkinson disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) all present with varying degrees of dysautonomia and are pathologically characterized by accumulation of alpha-synuclein. Hyposmia and olfactory pathway pathology are found in PD and MSA. We tested odor identification in 16 patients with PAF and compared the results with those found in patients with PD, patients with MSA, and control subjects.

The University of Pennsylvania Smell Identification Test (UPSIT) was used to evaluate the sense of smell in 16 patients with PAF, 14 patients with MSA, 191 patients with PD, and 145 control subjects. Multiple linear regression analyses were used to evaluate the effect of the diseases on the mean UPSIT score when adjusted for age, sex, and smoking habit.

The mean UPSIT score was higher in the controls than in patients with PAF (p < 0.001) or MSA (p < 0.001); it was lower in patients with PD than in patients with PAF (p = 0.005) or patients with MSA (p = 0.006); and no difference was found between patients with MSA and patients with PAF (p = 0.9) when adjusted for age, gender, and smoking habits.

Hyposmia may be a feature of pure autonomic failure (PAF), but to a lesser degree than that found in Parkinson disease. Further research into the olfactory pathways in patients with PAF is warranted.