Complex relationship between Parkin mutations and Parkinson disease

Abstract
Mutations in the Parkin gene cause juvenile and early onset Parkinsonism. While Parkin‐related disease is presumed to be an autosomal‐recessive disorder, cases have been reported where only a single Parkin allele is mutated and raise the possibility of a dominant effect. In this report, we re‐evaluate twenty heterozygous cases and extend the mutation screening to include the promoter and intron/exon boundaries. Novel deletion, point and intronic splice site mutations are described, along with promoter variation. These data, coupled with a complete review of published Parkin mutations, confirms that not only is recessive loss of Parkin a risk factor for juvenile and early onset Parkinsonism but that Parkin haploinsufficiency may be sufficient for disease in some cases.