However, Hague et al[23] indicated that the existence of the association between NOS1 exon29 polymorphism and PD risk in the study from Levecque et al[1] might be a false positive result, because the association between NOS1 exon29 and PD could not represent linkage disequilibrium with an unidentified pathogenic variant due to the constructed haplotypes across NOS1. This evidence concerns the gene NOS1 and Parkinson disease.