Although the implied pathogenicity of single heterozygous Parkin mutation contradicts the widely accepted notion that Parkin mutations transmit in a classical autosomal recessive manner, one could envisage that Parkin haploinsufficiency arising from such mutations could increase the risk of heterozygous Parkin carriers for PD especially in view of the importance of optimal Parkin expression to neuroprotection. This evidence concerns the gene PRKN and Parkinson disease.