The authors studied whether olfactory dysfunction is present in parkin disease using the University of Pennsylvania Smell Identification Test (UPSIT). The mean UPSIT score in parkin patients was 27.3 (95% CI 24.4 to 30.2). This did not differ from the normal group mean of 29.4 (95% CI 28.0 to 30.7; p = 0.22) but was higher than the Parkinson disease group (mean 14.3; 95% CI 12.2 to 19.5; p < 0.0001) and the parkin-negative group (mean 17.1; 95% CI 14.8 to 16.3; p < 0.0001) values. Parkin disease may be a distinct and separate entity from Parkinson disease.