OLFACTORY DYSFUNCTION IN FAMILIAL PARKINSONISM

Impaired olfactory function is commonly observed in idiopathic Parkins on's disease (TPD). However, it is unknown whether it is also found in familial parkinsonism. To address this issue we administered a smell test to 12 affected, three monosymptomatic, and 12 at-risk individuals from six large parkinsonian kindreds. Three kindreds exhibited an IPD phenotype and three exhibited a parkinsonism-plus syndrome (PPS) phen otype. All but one of the affected individuals had impaired olfactory function. In contrast, only five of the 12 at-risk individuals had imp aired olfactory function. The degree of olfactory impairment in the at -risk individuals was less severe than in the affected individuals. Th e difference in the degree of olfactory impairment in individuals exhi biting the TPD and tile PPS phenotypes was not statistically significa nt. These findings suggest that olfactory dysfunction is a phenotypic characteristic of familial parkinsonism and that it is independent of the kindred phenotype. The appearance of olfactory dysfunction soon af ter disease onset raises the possibility that it is part of the neurod egenerative disease process.